Discover Your Talent

Linked List

2009-02-07T16:33:00.001+05:30

Linked List Concepts

Printing Linked list without traversing the list:

void printreverse(Node *node)
{
if (node)
{
printreverse(node->next);
printf("%d -> ",node->info);
}
}

Reversing the list using stack:
Push all the nodes, pop one by one and print them… Here is the program for this..

void printreverse(Node* node)
{
Node *tmpnode;
Stack *stack = CreateStack();
while(node)
{
Push(stack, node);
node = node->next;
}
tmpnode = Pop(stack);
while(tmpnode)
{
tmpnode = Pop(stack);
printf("%d -> ", tmpnode->info);
}
DestroyStack(stack);
}
Reverse linked list using pointers
Reversing a single list can achieved using a stack very easily. however this can be done without using stack, and by simply using three additional pointers. Let us say we are using curr, next, result pointers, curr points to current node, next obviously points to the next node, result points to the new reversed linked list.
here is the pictorial representation of this operation for better understanding…

now result holds one reversed node, and curr points to the rest of the linked list..

now result holds a pointer to the reversed linked list (reversed two pointers already)…. curr holds rest of the list

we reversed successfully….

here is the routine for doing this…..
void reverse_single_linked_list(struct node** headRef)
{
struct node* result = NULL;
struct node* current = *headRef;
struct node* next;
while (current != NULL)
{
next = current->next; // tricky: note the next node
current->next = result; // move the node onto the result
result = current;
current = next;
}
*headRef = result;
Question: How could you determine if a linked list contains a cycle in it, and, at what node the cycle starts?
Answer: There are a number of approaches. The approach I shared is in time N (where N is the number of nodes in your linked list). Assume that the node definition contains a boolean flag, bVisited.
// error checking and checking for NULL at end of list omitted
p1 = p2 = head;

do {
p1 = p1->next;
p2 = p2->next->next;
} while (p1 != p2);
p2 is moving through the list twice as fast as p1. If the list is circular, (i.e. a cycle exists) it will eventually get around to that sluggard, p1.

Question: How would you reverse a doubly-linked list?
Answer: This problem isn't too hard. You just need to start at the head of the list, and iterate to the end. At each node, swap the values of pNext and pPrev. Finally, set pHead to the last node in the list.
Node * pCurrent = pHead, *pTemp;
while (pCurrent)
{
pTemp = pCurrent->pNext;
pCurrent->pNext = pCurrent->pPrev;
pCurrent->pPrev = temp;

pHead = pCurrent;

pCurrent = temp;
}
________________________________________
Question: Assume you have an array that contains a number of strings (perhaps char * a[100]). Each string is a word from the dictionary. Your task, described in high-level terms, is to devise a way to determine and display all of the anagrams within the array (two words are anagrams if they contain the same characters; for example, tales and slate are anagrams.)
Answer: Begin by sorting each element in the array in alphabetical order. So, if one element of your array was slate, it would be rearranged to form aelst (use some mechanism to know that the particular instance of aelst maps to slate). At this point, you slate and tales would be identical: aelst.
Next, sort the entire array of these modified dictionary words. Now, all of the anagrams are grouped together. Finally, step through the array and display duplicate terms, mapping the sorted letters (aelst) back to the word (slate or tales).
________________________________________
Question: Given the following prototype:
int compact(int * p, int size);
write a function that will take a sorted array, possibly with duplicates, and compact the array, returning the new length of the array. That is, if p points to an array containing: 1, 3, 7, 7, 8, 9, 9, 9, 10, when the function returns, the contents of p should be: 1, 3, 7, 8, 9, 10, with a length of 5 returned.
Answer: A single loop will accomplish this.
int compact(int * p, int size)
{
int current, insert = 1;
for (current=1; current < size; current++)
if (p[current] != p[insert-1])
{
p[insert] = p[current];
current++;
insert++;
} else
current++;
}
Happy Programming!

RE: write a c program to reverse the string without us...
________________________________________
#include
#include
main()
{
char str[50],revstr[50];
int i=0,j=0;
printf("Enter the string to be reversed : ");
scanf("%s",str);
for(i=strlen(str)-1;i>=0;i--)
{
revstr[j]=str[i];
j++;
}
revstr[j]='\0';
printf("Input String : %s",str);
printf("\nOutput String : %s",revstr);
getch();
}

write a c program to find whether a stack is
progressing in forward or reverse direction.

#include

void show_stack_dir(int * p) {
printf("%s\n", p < (int*)(&p) ? "up" : "down");
}

int main(int argc, char ** argv) {
show_stack_dir(&argc);
return 0;
}

Given a number, how can u determine using C, whether it is divisible by 3, without using *, /, % operators.

You may assume that itoa() function is available.
convert the number to the string using itoa();

add up all the digits
checkDivisibility(int num){
char *str=itoa(num)

while (1)
{
for (i =0 ; i < strlen(str);i++)
sum= sum + (str[i] - "0");

if (sum > 10)
str=itoa(sum);
else
break;
}

if(sum == 3 || sum == 6 || sum == 9)
printf("Number divisible by 3");
else
printf("Number not divisible by 3");

}

Re: Hexadecimal Conversion
« Reply #6 on: Jul 26th, 2007, 1:02am » Quote Modify

________________________________________
We can change this to...

if( ch >= '0' && ch <='9')
index=ch-'0';
else if(ch >= 'A' && ch <= 'F')
index=10+ch-'A';
else if(ch >='a' && ch <= 'f')
index=10+ch-'a';

Re: Find the Repeated Number
« Reply #5 on: Aug 1st, 2007, 3:20am » Quote Modify

________________________________________

Try and debug thru this code with an appropriate example

int findRepeated(int *arr,int length)
{
int counter=0;
int current=arr[0];
for(i=0;i{
if(counter==0)
{
counter++;
current=arr [ i ];
}
if(counter > 0)
{
if(current == arr [ i ])
{
counter++;
else
counter--;
}
}

return current;

}

Function for finding greatest of three numbers:
int maxof3(int a, int b, int c)
{
return (a + b + c * 2 + abs(a - b) + abs(a + b - c * 2 + abs(a - b))) / 4;
}
Function for finding greatest of four numbers:
int maxof4(int a, int b, int c, int d)
{
return (a + b + c + d + abs (b - a) + abs(d - c) + abs(a + b - c - d + abs( b - a) - abs(d - c)))/ 4;
}

GOOGLE CHROME - THE BEST WEB BROWSER

2009-02-07T16:27:00.000+05:30

GOOGLE CHROME

Google Chrome is a web browser developed by Google and based on the WebKit layout engine and application framework. In December 2008, it had a share of 1.04% of the browser market.[1] It was first released as a beta version for Microsoft Windows on September 2, 2008. The name is derived from the graphical user interface frame, or "chrome", of web browsers. The public stable release was on December 11, 2008.
• Chromium is the open source project behind Google Chrome.[2] The Google-authored portion of it is released under the BSD license, with other parts being subject to a variety of different permissive open-source licenses, including the MIT License, the LGPL, the Microsoft Permissive License and a MPL/GPL/LGPL tri-license.[3] It implements the same feature set as Chrome, but has a slightly different logo.
History
Announcement
The release announcement was originally scheduled for September 3, 2008, and a comic by Scott McCloud was to be sent to journalists and bloggers explaining the features of and motivations for the new browser.[5] Copies intended for Europe were shipped early and German blogger Philipp Lenssen of Google Blogoscoped[6] made a scanned copy of the 38-page comic available on his website after receiving it on September 1, 2008.[7] Google subsequently made the comic available on Google Books and their site[8] and mentioned it on its official blog along with an explanation for the early release.[9]
Public release

The Chromium Test Shell on Linux
The browser was first publicly released for Microsoft Windows (XP and later only) on September 2, 2008 in 43 languages, officially a beta version.[10] Chrome quickly gained about 1% market share. Mac OS X and Linux versions are under development.[11][12][13][14] Recently, in the Chromium project's developer wiki[15] a message was placed that a "test shell" is available to build on Linux. Some have tried this shell, which apparently lacks many features, but appears to function quite well in rendering web sites (including JavaScript).[16][17]
On September 2, a CNET news item[18] drew attention to a passage in the terms of service for the initial beta release, which seemed to grant to Google a license to all content transferred via the Chrome browser. The passage in question was inherited from the general Google terms of service.[19] On the same day, Google responded to this criticism by stating that the language used was borrowed from other products, and removed the passage in question from the Terms of Service.[20] Google noted that this change would "apply retroactively to all users who have downloaded Google Chrome."[21] There were subsequent concern and confusion about whether and what information the program communicates back to Google. The company stated[22] that usage metrics are only sent when users opt in by checking the option "help make Google Chrome better by automatically sending usage statistics and crash reports to Google" when the browser is installed.[23]
The first release of Google Chrome passed the Acid1 and Acid2 tests. It also passed 79 out of the 100 subtests of the Acid3, higher than both Internet Explorer 7 (14) and Firefox 3 (71), but lower than Opera (83)[vague].[24] When compared with development builds of Firefox, Internet Explorer, Opera, and Safari, Chrome scored lower than Firefox 3.1 Beta 1 (85), Opera (100), and Safari 4 (Developer Preview) (100),[24] but still higher than Internet Explorer (21)[citation needed].
On January 9, 2009, CNET reports that Google plans to release versions for Mac OS X and Linux by the first half of the year.[25]
Unofficial Chromium releases
• On September 15, 2008, CodeWeavers released an unofficial bundle of a Wine derivative and Chromium Developer Build 21 for Linux and Mac OS X, which they dubbed CrossOver Chromium.[26][27]
• SRWare Iron is a release of Chromium software that explicitly disables the collection and transmission of usage information to Google which is optional within Chrome.[28]
Development
Primary design goals were improvements in security, speed, and stability compared to existing browsers. There also were extensive changes in the user interface.[8] Chrome was assembled from 26 different code libraries from Google and others from third parties such as Netscape.[29]
Security
Chrome periodically downloads updates of two blacklists (one for phishing and one for malware), and warns users when they attempt to visit a harmful site. This service is also made available for use by others via a free public API called "Google Safe Browsing API". Google notifies the owners of listed sites who may not be aware of the presence of the harmful software.[8]
Chrome will typically allocate each tab to fit into its own process to "prevent malware from installing itself" or "using what happens in one tab to affect what happens in another", however the actual process allocation model is more complex.[30] Following the principle of least privilege, each process is stripped of its rights and can compute, but can not write files or read from sensitive areas (e.g. documents, desktop)—this is similar to the "Protected Mode" that is used by Internet Explorer 7 on Windows Vista. The Sandbox Team is said to have "taken this existing process boundary and made it into a jail";[31] for example, malicious software running in one tab is unable to sniff credit card numbers, interact with the mouse, or tell "Windows to run an executable on start-up" and it will be terminated when the tab is closed. This enforces a simple computer security model whereby there are two levels of multilevel security (user and sandbox) and the sandbox can only respond to communication requests initiated by the user.[32]
Typically, plugins such as Adobe Flash Player are not standardized and as such, cannot be sandboxed as tabs can be. These often need to run at, or above, the security level of the browser itself. To reduce exposure to attack, plugins are run in separate processes that communicate with the renderer, itself operating at "very low privileges" in dedicated per-tab processes. Plugins will need to be modified to operate within this software architecture while following the principle of least privilege.[8] Chrome supports the Netscape Plugin Application Programming Interface (NPAPI),[33][34] but does not support the embedding of ActiveX controls.[34] Also, Chrome does not have an extension system such as Mozilla's XPInstall architecture.[35] Java applets support is available in Chrome as part of Java 6 update 11, which currently is the latest stable version.[36][37]
A private browsing feature called Incognito mode is provided that prevents the browser from storing any history information or cookies from the websites visited. This feature has been referred to as a porn mode similar to the private browsing feature available in Apple's Safari and the latest beta version of Internet Explorer 8.[38]
A denial-of-service vulnerability was found that allowed a malicious web page to crash the whole web browser.[39][40] However, Google Chrome developers confirmed the flaw, and it was fixed in the 0.2.149.29 release.[41]
Speed
The JavaScript virtual machine was considered a sufficiently important project to be split off (as was Adobe/Mozilla's Tamarin) and handled by a separate team in Denmark. According to Google, existing implementations were designed "for small programs, where the performance and interactivity of the system weren't that important," but web applications such as Gmail "are using the web browser to the fullest when it comes to DOM manipulations and Javascript." The resulting V8 JavaScript engine has features such as hidden class transitions, dynamic code generation, and precise garbage collection.[8] Tests by Google showed that V8 was about twice as fast as Firefox 3.0 and the Safari 4 beta.[42]
Several websites performed benchmark tests using the SunSpider JavaScript Benchmark[43] tool as well as Google's own set of computationally intense benchmarks, which includes ray tracing and constraint solving.[44] They unanimously reported that Chrome performed much faster than all competitors against which it had been tested, including Safari, Firefox 3.0, Internet Explorer 7, and Internet Explorer 8.[45][46][47][48] While Opera had not been compared to Chrome in those comparisons, in previous tests, it had been shown to be slightly slower than Firefox 3.0, which in turn, was slower than Chrome.[49][50] Another blog post by Mozilla developer Brendan Eich compared Chrome's V8 engine to his own TraceMonkey Javascript engine which was introduced in Firefox 3.1alpha, stating that some tests were faster in one engine and some were faster in the other, with Firefox 3.1a faster overall.[51] John Resig, Mozilla's JavaScript evangelist, further commented on the performance of different browsers on Google's own suite, finding Chrome "decimating" other browsers, but he questions whether Google's suite is representative of real programs. He stated that Firefox 3.0 performed poorly on recursion intensive benchmarks, such as those of Google, because the Mozilla team had not implemented recursion-tracing yet.[52]
Chrome also uses DNS prefetching to speed up website lookups.[53]
Stability
The Gears team was considering a multithreaded browser (noting that a problem with existing web browser implementations was that they are inherently single-threaded) and Chrome implemented this concept with a multi-process architecture,[54] similar to Loosely Coupled Internet Explorer (LCIE) recently implemented by Internet Explorer 8.[55] By default, a separate process is allocated to each site instance and plugin.[56] This prevents tasks from interfering with each other, which is good for security and stability; an attacker successfully gaining access to one application does not gain access to all, and failure in one application results in a Sad Tab screen of death, similar to the well-known Sad Mac, except only one single tab crashes instead of the whole application. This strategy exacts a fixed per-process cost up front, but results in less memory bloat overall as fragmentation is confined to each process and no longer results in further memory allocations.[57]
Chrome features a process management utility called the Task Manager which allows the user to "see what sites are using the most memory, downloading the most bytes and abusing [their] CPU" (as well as the plugins which run in separate processes) and terminate them.[8] Some users have reported a conflict with Internet Explorer, often resulting in the blue screen error on Windows.[58]
User interface

When Chrome is maximized, the title bar becomes hidden and instead, the tab bar is displayed at the top. Also, when the mouse is moved over a link, the URL of the link is displayed in a status bar at the bottom left. Otherwise, the status bar is invisible.

When Chrome is not maximized, the title bar is shown on top of the tab bar.
The main user interface includes back, forward, refresh, bookmark, go, and cancel options. The options are similar to Safari, while the location of the settings is similar to versions of Internet Explorer starting with version 7. The design of the window is based on Windows Vista.
When the window is not maximized, the tab bar appears directly under the title bar. When maximized, the title bar disappears, and instead, the tab bar is shown at the very top of the window. Unlike other browsers such as Internet Explorer or Firefox which also have a full-screen mode that hides the operating system's interface completely, Chrome can only be maximized like a standard Windows application. Therefore, the Windows task bar, notification area, and start menu link still take space at all times unless they have been configured to hide at all times.
Chrome includes Gears, which adds features for web developers typically relating to the building of web applications (including offline support).[8]
Chrome replaces the browser home page which is displayed when a new tab is created with a New Tab Page. This shows[59] thumbnails of the nine most visited web sites along with the sites most often searched, recent bookmarks, and recently closed tabs.[8]
The Omnibox is the URL box at the top of each tab, which combines the functionalities of both URL box and search box. It includes autocomplete functionality, but only will autocomplete URLs that were manually entered (rather than all links), search suggestions, top pages (previously visited), popular pages (unvisited), and text search over history. Search engines also can be captured by the browser when used via the native user interface by pressing Tab.[8]
Popup windows "are scoped to the tab they came from" and will not appear outside the tab unless the user explicitly drags them out.[8]
Chrome uses the WebKit rendering engine to display web pages, on advice from the Android team.[8] Like most browsers, Chrome was extensively tested internally before release with unit testing, "automated user interface testing of scripted user actions" and fuzz testing, as well as WebKit's layout tests (99% of which Chrome is claimed to have passed). New browser builds are automatically tested against tens of thousands of commonly accessed websites inside of the Google index within 20-30 minutes.[8]
Tabs are the primary component of Chrome's user interface and as such, have been moved to the top of the window rather than below the controls. This subtle change contrasts with many existing tabbed browsers which are based on windows and contain tabs. Tabs (including their state) can be transferred seamlessly between window containers by dragging. Each tab has its own set of controls, including the Omnibox.[8]
Chrome allows users to make local desktop shortcuts that open web applications in the browser. The browser, when opened in this way, contains none of the regular interface except for the title bar, so as not to "interrupt anything the user is trying to do." This allows web applications to run alongside local software (similar to Mozilla Prism and Fluid).[8]
By default, the status bar is hidden whenever it is not being used. However, it appears at the bottom left corner whenever a page is loading and when a hyperlink is hovered over.
For web developers, Chrome features an element inspector similar to the one in Firebug.[53]
Usage tracking
Usage tracking is an option presented to the user during the software's installation. Once accepted, it is possible to disable the transmission of this information by modifying Chrome's "Under the Hood" options.[60] Freeware programs such as UnChrome can remove the unique ID without having to change the browser.[61] Unofficial builds, such as SRWare Iron, seek to remove these features from the browser altogether.[62]
Extensions
As of October 2008, Google Chrome does not support 3rd party extensions.[63][64]
As of version 3499, Google Chrome has rudimentary Greasemonkey support. This feature is off by default, and may be turned on by launching the application with a specific command-line argument.
Google Chrome extensions: Not yet, but later. "We don't have that in the beta today, but we definitely plan an extension API," or application programming interface, Sundar Pichai, a Google vice president of product management, said at the Chrome launch event here Tuesday. "It is one of the things we will get to next."
—CNet News
Stable, Beta and Dev Releases
On January 08, 2009 Google introduced a new release channels system, whereby now there are three distinct release channels: Stable channel, Beta channel, and Developer preview channel. Before this change, there were only two channels: Beta channel and Developer preview channel. All previous Dev channel users were moved to Beta channel, the reason is that now the new Dev channel builds will be less stable and polished than what Dev channel users have been getting during Google Chrome's Beta period. Now the stable channel will be updated with features and fixes once they have been thoroughly tested in the Beta channel, and the Beta channel will be updated roughly monthly with stable and complete features from the Dev channel. The Dev channel is where ideas get tested (and sometimes fail), and it can be very unstable at times. [67][68] See http://googlechromereleases.blogspot.com/ for more information on specific releases.
Reception
The Daily Telegraph's Matthew Moore summarizes the verdict of early reviewers: "Google Chrome is attractive, fast and has some impressive new features, but may not—yet—be a threat to its Microsoft rival."[69]
Microsoft reportedly "played down the threat from Chrome" and "predicted that most people will embrace Internet Explorer 8." Opera Software said that "Chrome will strengthen the Web as the biggest application platform in the world."[70] Mozilla said that Chrome's introduction into the web browser market comes as "no real surprise", that "Chrome is not aimed at competing with Firefox", and furthermore that it should not affect Google's financing of Firefox.[71][72]
Chrome’s design bridges the gap between desktop and so-called “cloud computing.” At the touch of a button, Chrome lets you make a desktop, Start menu, or Quick Launch shortcut to any Web page or Web application, blurring the line between what’s online and what’s inside your PC. For example, I created a desktop shortcut for Google Maps. When you create a shortcut for a Web application, Chrome strips away all of the toolbars and tabs from the window, leaving you with something that feels much more like a desktop application than like a Web application or page.
—PC World[73]
On September 9, 2008, when Chrome still had been in beta, the German Federal Office for Information Security (BSI) issued a statement about their first examination of Chrome, expressing a concern over the prominent download links on Google's German web page, because "beta versions should not be employed for general use applications" and browser manufacturers should provide appropriate instructions regarding the use of pre-released software. They did, however, praise the browser's technical contribution to improving security on the web.[74]
Concern about Chrome's optional usage collection and tracking have been noted in several publications.[75][76]

Java Interview Questions

2009-02-07T16:25:00.000+05:30

Java Interview Questions

Question: What is the difference between an Interface and an Abstract class?

Question: What is the purpose of garbage collection in Java, and when is it used?

Question: Describe synchronization in respect to multithreading.

Question: Explain different way of using thread?

Question: What are pass by reference and passby value?

Question: What is HashMap and Map?

Question: Difference between HashMap and HashTable?

Question: Difference between Vector and ArrayList?

Question: Difference between Swing and Awt?

Question: What is the difference between a constructor and a method?

Question: What is an Iterator?

Question: State the significance of public, private, protected, default modifiers both singly and in combination and state the effect of package relationships on declared items qualified by these modifiers.

Question: What is an abstract class?

Question: What is static in java?

Question: What is final?

Q: What is the difference between an Interface and an Abstract class?
A: An abstract class can have instance methods that implement a default behavior. An Interface can only declare constants and instance methods, but cannot implement default behavior and all methods are implicitly abstract. An interface has all public members and no implementation. An abstract class is a class which may have the usual flavors of class members (private, protected, etc.), but has some abstract methods.
.

Q: What is the purpose of garbage collection in Java, and when is it used?
A: The purpose of garbage collection is to identify and discard objects that are no longer needed by a program so that their resources can be reclaimed and reused. A Java object is subject to garbage collection when it becomes unreachable to the program in which it is used.

Q: Describe synchronization in respect to multithreading.
A: With respect to multithreading, synchronization is the capability to control the access of multiple threads to shared resources. Without synchonization, it is possible for one thread to modify a shared variable while another thread is in the process of using or updating same shared variable. This usually leads to significant errors.

Q: Explain different way of using thread?
A: The thread could be implemented by using runnable interface or by inheriting from the Thread class. The former is more advantageous, 'cause when you are going for multiple inheritance..the only interface can help.

Q: What are pass by reference and passby value?
A: Pass By Reference means the passing the address itself rather than passing the value. Passby Value means passing a copy of the value to be passed.

Q: What is HashMap and Map?
A: Map is Interface and Hashmap is class that implements that.

Q: Difference between HashMap and HashTable?
A: The HashMap class is roughly equivalent to Hashtable, except that it is unsynchronized and permits nulls. (HashMap allows null values as key and value whereas Hashtable doesnt allow). HashMap does not guarantee that the order of the map will remain constant over time. HashMap is unsynchronized and Hashtable is synchronized.

Q: Difference between Vector and ArrayList?
A: Vector is synchronized whereas arraylist is not.

Q: Difference between Swing and Awt?
A: AWT are heavy-weight componenets. Swings are light-weight components. Hence swing works faster than AWT.

Q: What is the difference between a constructor and a method?
A: A constructor is a member function of a class that is used to create objects of that class. It has the same name as the class itself, has no return type, and is invoked using the new operator.
A method is an ordinary member function of a class. It has its own name, a return type (which may be void), and is invoked using the dot operator.

Q: What is an Iterator?
A: Some of the collection classes provide traversal of their contents via a java.util.Iterator interface. This interface allows you to walk through a collection of objects, operating on each object in turn. Remember when using Iterators that they contain a snapshot of the collection at the time the Iterator was obtained; generally it is not advisable to modify the collection itself while traversing an Iterator.

Q: State the significance of public, private, protected, default modifiers both singly and in combination and state the effect of package relationships on declared items qualified by these modifiers.
A: public : Public class is visible in other packages, field is visible everywhere (class must be public too)
private : Private variables or methods may be used only by an instance of the same class that declares the variable or method, A private feature may only be accessed by the class that owns the feature.
protected : Is available to all classes in the same package and also available to all subclasses of the class that owns the protected feature.This access is provided even to subclasses that reside in a different package from the class that owns the protected feature.
default :What you get by default ie, without any access modifier (ie, public private or protected).It means that it is visible to all within a particular package.

Q: What is an abstract class?
A: Abstract class must be extended/subclassed (to be useful). It serves as a template. A class that is abstract may not be instantiated (ie, you may not call its constructor), abstract class may contain static data. Any class with an abstract method is automatically abstract itself, and must be declared as such.
A class may be declared abstract even if it has no abstract methods. This prevents it from being instantiated.

Q: What is static in java?
A: Static means one per class, not one for each object no matter how many instance of a class might exist. This means that you can use them without creating an instance of a class.Static methods are implicitly final, because overriding is done based on the type of the object, and static methods are attached to a class, not an object. A static method in a superclass can be shadowed by another static method in a subclass, as long as the original method was not declared final. However, you can't override a static method with a nonstatic method. In other words, you can't change a static method into an instance method in a subclass.

Q: What is final?
A: A final class can't be extended ie., final class may not be subclassed. A final method can't be overridden when its class is inherited. You can't change value of a final variable (is a constant).
Java Interview Questions

Question: What if the main method is declared as private?

Question: What if the static modifier is removed from the signature of the main method?

Question: What if I write static public void instead of public static void?

Question: What if I do not provide the String array as the argument to the method?

Question: What is the first argument of the String array in main method?

Question: If I do not provide any arguments on the command line, then the String array of Main method will be empty or null?

Question: How can one prove that the array is not null but empty using one line of code?

Question: What environment variables do I need to set on my machine in order to be able to run Java programs?

Question: Can an application have multiple classes having main method?

Question: Can I have multiple main methods in the same class?

Question: Do I need to import java.lang package any time? Why ?

Question: Can I import same package/class twice? Will the JVM load the package twice at runtime?

Question: What are Checked and UnChecked Exception?

Question: What is Overriding?

Question: What are different types of inner classes?

Q: What if the main method is declared as private?
A: The program compiles properly but at runtime it will give "Main method not public." message.
[ Received from Sandesh Sadhale]

Q: What if the static modifier is removed from the signature of the main method?
A: Program compiles. But at runtime throws an error "NoSuchMethodError".
[ Received from Sandesh Sadhale]

Q: What if I write static public void instead of public static void?
A: Program compiles and runs properly.
[ Received from Sandesh Sadhale]

Q: What if I do not provide the String array as the argument to the method?
A: Program compiles but throws a runtime error "NoSuchMethodError".
[ Received from Sandesh Sadhale]

Q: What is the first argument of the String array in main method?
A: The String array is empty. It does not have any element. This is unlike C/C++ where the first element by default is the program name.
[ Received from Sandesh Sadhale]

Q: If I do not provide any arguments on the command line, then the String array of Main method will be empty or null?
A: It is empty. But not null.
[ Received from Sandesh Sadhale]

Q: How can one prove that the array is not null but empty using one line of code?
A: Print args.length. It will print 0. That means it is empty. But if it would have been null then it would have thrown a NullPointerException on attempting to print args.length.
[ Received from Sandesh Sadhale]

Q: What environment variables do I need to set on my machine in order to be able to run Java programs?
A: CLASSPATH and PATH are the two variables.
[ Received from Sandesh Sadhale]

Q: Can an application have multiple classes having main method?
A: Yes it is possible. While starting the application we mention the class name to be run. The JVM will look for the Main method only in the class whose name you have mentioned. Hence there is not conflict amongst the multiple classes having main method.
[ Received from Sandesh Sadhale]

Q: Can I have multiple main methods in the same class?
A: No the program fails to compile. The compiler says that the main method is already defined in the class.
[ Received from Sandesh Sadhale]

Q: Do I need to import java.lang package any time? Why ?
A: No. It is by default loaded internally by the JVM.
[ Received from Sandesh Sadhale]

Q: Can I import same package/class twice? Will the JVM load the package twice at runtime?
A: One can import the same package or same class multiple times. Neither compiler nor JVM complains abt it. And the JVM will internally load the class only once no matter how many times you import the same class.
[ Received from Sandesh Sadhale]

Q: What are Checked and UnChecked Exception?
A: A checked exception is some subclass of Exception (or Exception itself), excluding class RuntimeException and its subclasses.
Making an exception checked forces client programmers to deal with the possibility that the exception will be thrown. eg, IOException thrown by java.io.FileInputStream's read() method•
Unchecked exceptions are RuntimeException and any of its subclasses. Class Error and its subclasses also are unchecked. With an unchecked exception, however, the compiler doesn't force client programmers either to catch the
exception or declare it in a throws clause. In fact, client programmers may not even know that the exception could be thrown. eg, StringIndexOutOfBoundsException thrown by String's charAt() method• Checked exceptions must be caught at compile time. Runtime exceptions do not need to be. Errors often cannot be.

Q: What is Overriding?
A: When a class defines a method using the same name, return type, and arguments as a method in its superclass, the method in the class overrides the method in the superclass.
When the method is invoked for an object of the class, it is the new definition of the method that is called, and not the method definition from superclass. Methods may be overridden to be more public, not more private.

Q: What are different types of inner classes?
A: Nested -level classes, Member classes, Local classes, Anonymous classes
Nested -level classes- If you declare a class within a class and specify the static modifier, the compiler treats the class just like any other -level class.
Any class outside the declaring class accesses the nested class with the declaring class name acting similarly to a package. eg, outer.inner. -level inner classes implicitly have access only to static variables.There can also be inner interfaces. All of these are of the nested -level variety.

Member classes - Member inner classes are just like other member methods and member variables and access to the member class is restricted, just like methods and variables. This means a public member class acts similarly to a nested -level class. The primary difference between member classes and nested -level classes is that member classes have access to the specific instance of the enclosing class.

Local classes - Local classes are like local variables, specific to a block of code. Their visibility is only within the block of their declaration. In order for the class to be useful beyond the declaration block, it would need to implement a
more publicly available interface.Because local classes are not members, the modifiers public, protected, private, and static are not usable.

Anonymous classes - Anonymous inner classes extend local inner classes one level further. As anonymous classes have no name, you cannot provide a constructor.

Java Interview Questions

Question: Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?

Question: Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?

Question: What is the difference between declaring a variable and defining a variable?

Question: What is the default value of an object reference declared as an instance variable?

Question: Can a level class be private or protected?

Question: What type of parameter passing does Java support?

Question: Primitive data types are passed by reference or pass by value?

Question: Objects are passed by value or by reference?

Question: What is serialization?

Question: How do I serialize an object to a file?

Question: Which methods of Serializable interface should I implement?

Question: How can I customize the seralization process? i.e. how can one have a control over the serialization process?

Question: What is the common usage of serialization?

Question: What is Externalizable interface?

Question: When you serialize an object, what happens to the object references included in the object?

Question: What one should take care of while serializing the object?

Question: What happens to the static fields of a class during serialization?

Q: Are the imports checked for validity at compile time? e.g. will the code containing an import such as java.lang.ABCD compile?
A: Yes the imports are checked for the semantic validity at compile time. The code containing above line of import will not compile. It will throw an error saying,can not resolve symbol
symbol : class ABCD
location: package io
import java.io.ABCD;
[ Received from Sandesh Sadhale]

Q: Does importing a package imports the subpackages as well? e.g. Does importing com.MyTest.* also import com.MyTest.UnitTests.*?
A: No you will have to import the subpackages explicitly. Importing com.MyTest.* will import classes in the package MyTest only. It will not import any class in any of it's subpackage.
[ Received from Sandesh Sadhale]

Q: What is the difference between declaring a variable and defining a variable?
A: In declaration we just mention the type of the variable and it's name. We do not initialize it. But defining means declaration + initialization.
e.g String s; is just a declaration while String s = new String ("abcd"); Or String s = "abcd"; are both definitions.
[ Received from Sandesh Sadhale]

Q: What is the default value of an object reference declared as an instance variable?
A: null unless we define it explicitly.
[ Received from Sandesh Sadhale]

Q: Can a level class be private or protected?
A: No. A level class can not be private or protected. It can have either "public" or no modifier. If it does not have a modifier it is supposed to have a default access.If a level class is declared as private the compiler will complain that the "modifier private is not allowed here". This means that a level class can not be private. Same is the case with protected.
[ Received from Sandesh Sadhale]

Q: What type of parameter passing does Java support?
A: In Java the arguments are always passed by value .
[ Update from Eki and Jyothish Venu]

Q: Primitive data types are passed by reference or pass by value?
A: Primitive data types are passed by value.
[ Received from Sandesh Sadhale]

Q: Objects are passed by value or by reference?
A: Java only supports pass by value. With objects, the object reference itself is passed by value and so both the original reference and parameter copy both refer to the same object .
[ Update from Eki and Jyothish Venu]

Q: What is serialization?
A: Serialization is a mechanism by which you can save the state of an object by converting it to a byte stream.
[ Received from Sandesh Sadhale]

Q: How do I serialize an object to a file?
A: The class whose instances are to be serialized should implement an interface Serializable. Then you pass the instance to the ObjectOutputStream which is connected to a fileoutputstream. This will save the object to a file.
[ Received from Sandesh Sadhale]

Q: Which methods of Serializable interface should I implement?
A: The serializable interface is an empty interface, it does not contain any methods. So we do not implement any methods.
[ Received from Sandesh Sadhale]

Q: How can I customize the seralization process? i.e. how can one have a control over the serialization process?
A: Yes it is possible to have control over serialization process. The class should implement Externalizable interface. This interface contains two methods namely readExternal and writeExternal. You should implement these methods and write the logic for customizing the serialization process.
[ Received from Sandesh Sadhale]

Q: What is the common usage of serialization?
A: Whenever an object is to be sent over the network, objects need to be serialized. Moreover if the state of an object is to be saved, objects need to be serilazed.
[ Received from Sandesh Sadhale]

Q: What is Externalizable interface?
A: Externalizable is an interface which contains two methods readExternal and writeExternal. These methods give you a control over the serialization mechanism. Thus if your class implements this interface, you can customize the serialization process by implementing these methods.
[ Received from Sandesh Sadhale]

Q: When you serialize an object, what happens to the object references included in the object?
A: The serialization mechanism generates an object graph for serialization. Thus it determines whether the included object references are serializable or not. This is a recursive process. Thus when an object is serialized, all the included objects are also serialized alongwith the original obect.
[ Received from Sandesh Sadhale]

Q: What one should take care of while serializing the object?
A: One should make sure that all the included objects are also serializable. If any of the objects is not serializable then it throws a NotSerializableException.
[ Received from Sandesh Sadhale]

Q: What happens to the static fields of a class during serialization?
A: There are three exceptions in which serialization doesnot necessarily read and write to the stream. These are
1. Serialization ignores static fields, because they are not part of ay particular state state.
2. Base class fields are only hendled if the base class itself is serializable.
3. Transient fields.
[ Received from Sandesh Sadhale Modified after P.John David comments.]

Java Interview Questions

Question: Does Java provide any construct to find out the size of an object?

Question: Give a simplest way to find out the time a method takes for execution without using any profiling tool?

Question: What are wrapper classes?

Question: Why do we need wrapper classes?

Question: What are checked exceptions?

Question: What are runtime exceptions?

Question: What is the difference between error and an exception??

Question: How to create custom exceptions?

Question: If I want an object of my class to be thrown as an exception object, what should I do?

Question: If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?

Question: How does an exception permeate through the code?

Question: What are the different ways to handle exceptions?

Question: What is the basic difference between the 2 approaches to exception handling...1> try catch block and 2> specifying the candidate exceptions in the throws clause?
When should you use which approach?

Question: Is it necessary that each try block must be followed by a catch block?

Question: If I write return at the end of the try block, will the finally block still execute?

Question: If I write System.exit (0); at the end of the try block, will the finally block still execute?

Q: Does Java provide any construct to find out the size of an object?
A: No there is not sizeof operator in Java. So there is not direct way to determine the size of an object directly in Java.
[ Received from Sandesh Sadhale]

Q: Give a simplest way to find out the time a method takes for execution without using any profiling tool?
A: Read the system time just before the method is invoked and immediately after method returns. Take the time difference, which will give you the time taken by a method for execution.
To put it in code...
long start = System.currentTimeMillis ();
method ();
long end = System.currentTimeMillis ();
System.out.println ("Time taken for execution is " + (end - start));
Remember that if the time taken for execution is too small, it might show that it is taking zero milliseconds for execution. Try it on a method which is big enough, in the sense the one which is doing considerable amout of processing.
[ Received from Sandesh Sadhale]

Q: What are wrapper classes?
A: Java provides specialized classes corresponding to each of the primitive data types. These are called wrapper classes. They are e.g. Integer, Character, Double etc.
[ Received from Sandesh Sadhale]

Q: Why do we need wrapper classes?
A: It is sometimes easier to deal with primitives as objects. Moreover most of the collection classes store objects and not primitive data types. And also the wrapper classes provide many utility methods also. Because of these resons we need wrapper classes. And since we create instances of these classes we can store them in any of the collection classes and pass them around as a collection. Also we can pass them around as method parameters where a method expects an object.
[ Received from Sandesh Sadhale]

Q: What are checked exceptions?
A: Checked exception are those which the Java compiler forces you to catch. e.g. IOException are checked Exceptions.
[ Received from Sandesh Sadhale]

Q: What are runtime exceptions?
A: Runtime exceptions are those exceptions that are thrown at runtime because of either wrong input data or because of wrong business logic etc. These are not checked by the compiler at compile time.
[ Received from Sandesh Sadhale]

Q: What is the difference between error and an exception?
A: An error is an irrecoverable condition occurring at runtime. Such as OutOfMemory error. These JVM errors and you can not repair them at runtime. While exceptions are conditions that occur because of bad input etc. e.g. FileNotFoundException will be thrown if the specified file does not exist. Or a NullPointerException will take place if you try using a null reference. In most of the cases it is possible to recover from an exception (probably by giving user a feedback for entering proper values etc.).
[ Received from Sandesh Sadhale]

Q: How to create custom exceptions?
A: Your class should extend class Exception, or some more specific type thereof.
[ Received from Sandesh Sadhale]

Q: If I want an object of my class to be thrown as an exception object, what should I do?
A: The class should extend from Exception class. Or you can extend your class from some more precise exception type also.
[ Received from Sandesh Sadhale]

Q: If my class already extends from some other class what should I do if I want an instance of my class to be thrown as an exception object?
A: One can not do anytihng in this scenarion. Because Java does not allow multiple inheritance and does not provide any exception interface as well.
[ Received from Sandesh Sadhale]

Q: How does an exception permeate through the code?
A: An unhandled exception moves up the method stack in search of a matching When an exception is thrown from a code which is wrapped in a try block followed by one or more catch blocks, a search is made for matching catch block. If a matching type is found then that block will be invoked. If a matching type is not found then the exception moves up the method stack and reaches the caller method. Same procedure is repeated if the caller method is included in a try catch block. This process continues until a catch block handling the appropriate type of exception is found. If it does not find such a block then finally the program terminates.
[ Received from Sandesh Sadhale]

Q: What are the different ways to handle exceptions?
A: There are two ways to handle exceptions,
1. By wrapping the desired code in a try block followed by a catch block to catch the exceptions. and
2. List the desired exceptions in the throws clause of the method and let the caller of the method hadle those exceptions.
[ Received from Sandesh Sadhale]

Q: What is the basic difference between the 2 approaches to exception handling.
1> try catch block and
2> specifying the candidate exceptions in the throws clause?
When should you use which approach?
A: In the first approach as a programmer of the method, you urself are dealing with the exception. This is fine if you are in a best position to decide should be done in case of an exception. Whereas if it is not the responsibility of the method to deal with it's own exceptions, then do not use this approach. In this case use the second approach. In the second approach we are forcing the caller of the method to catch the exceptions, that the method is likely to throw. This is often the approach library creators use. They list the exception in the throws clause and we must catch them. You will find the same approach throughout the java libraries we use.
[ Received from Sandesh Sadhale]

Q: Is it necessary that each try block must be followed by a catch block?
A: It is not necessary that each try block must be followed by a catch block. It should be followed by either a catch block OR a finally block. And whatever exceptions are likely to be thrown should be declared in the throws clause of the method.
[ Received from Sandesh Sadhale]

Q: If I write return at the end of the try block, will the finally block still execute?
A: Yes even if you write return as the last statement in the try block and no exception occurs, the finally block will execute. The finally block will execute and then the control return.
[ Received from Sandesh Sadhale]

Q: If I write System.exit (0); at the end of the try block, will the finally block still execute?
A: No in this case the finally block will not execute because when you say System.exit (0); the control immediately goes out of the program, and thus finally never executes.
[ Received from Sandesh Sadhale]

Java Interview Questions

Question: How are Observer and Observable used?

Question: What is synchronization and why is it important?

Question: How does Java handle integer overflows and underflows?

Question: Does garbage collection guarantee that a program will not run out of
memory?

Question: What is the difference between preemptive scheduling and time slicing?

Question: When a thread is created and started, what is its initial state?

Question: What is the purpose of finalization?

Question: What is the Locale class?

Question: What is the difference between a while statement and a do statement?

Question: What is the difference between static and non-static variables?

Question: How are this() and super() used with constructors?

Question: What are synchronized methods and synchronized statements?

Question: What is daemon thread and which method is used to create the daemon thread?

Question: Can applets communicate with each other?

Question: What are the steps in the JDBC connection?

Question: How does a try statement determine which catch clause should be used to handle an exception?

Q: How are Observer and Observable used?
A: Objects that subclass the Observable class maintain a list of observers. When an Observable object is updated it invokes the update() method of each of its observers to notify the observers that it has changed state. The Observer interface is implemented by objects that observe Observable objects.
[Received from Venkateswara Manam]

Q: What is synchronization and why is it important?
A: With respect to multithreading, synchronization is the capability to control
the access of multiple threads to shared resources. Without synchronization, it is possible for one thread to modify a shared object while another thread is in the process of using or updating that object's value. This often leads to significant errors.
[ Received from Venkateswara Manam]

Q: How does Java handle integer overflows and underflows?
A: It uses those low order bytes of the result that can fit into the size of the type allowed by the operation.
[ Received from Venkateswara Manam]

Q: Does garbage collection guarantee that a program will not run out of memory?
A: Garbage collection does not guarantee that a program will not run out of memory. It is possible for programs to use up memory resources faster than they are garbage collected. It is also possible for programs to create objects that are not subject to garbage collection
.
[ Received from Venkateswara Manam]

Q: What is the difference between preemptive scheduling and time slicing?
A: Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.
[ Received from Venkateswara Manam]

Q: When a thread is created and started, what is its initial state?
A: A thread is in the ready state after it has been created and started.
[ Received from Venkateswara Manam]

Q: What is the purpose of finalization?
A: The purpose of finalization is to give an unreachable object the opportunity to perform any cleanup processing before the object is garbage collected.
[ Received from Venkateswara Manam]

Q: What is the Locale class?
A: The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region.
[ Received from Venkateswara Manam]

Q: What is the difference between a while statement and a do statement?
A: A while statement checks at the beginning of a loop to see whether the next loop iteration should occur. A do statement checks at the end of a loop to see whether the next iteration of a loop should occur. The do statement will always execute the body of a loop at least once.
[ Received from Venkateswara Manam]

Q: What is the difference between static and non-static variables?
A: A static variable is associated with the class as a whole rather than with specific instances of a class. Non-static variables take on unique values with each object instance.
[ Received from Venkateswara Manam]

Q: How are this() and super() used with constructors?
A: This() is used to invoke a constructor of the same class. super() is used to invoke a superclass constructor.
[ Received from Venkateswara Manam]

Q: What are synchronized methods and synchronized statements?
A: Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
[ Received from Venkateswara Manam]

Q: What is daemon thread and which method is used to create the daemon thread?
A: Daemon thread is a low priority thread which runs intermittently in the back ground doing the garbage collection operation for the java runtime system. setDaemon method is used to create a daemon thread.
[ Received from Shipra Kamra]

Q: Can applets communicate with each other?
A: At this point in time applets may communicate with other applets running in the same virtual machine. If the applets are of the same class, they can communicate via shared static variables. If the applets are of different classes, then each will need a reference to the same class with static variables. In any case the basic idea is to pass the information back and forth through a static variable.

An applet can also get references to all other applets on the same page using the getApplets() method of java.applet.AppletContext. Once you get the reference to an applet, you can communicate with it by using its public members.

It is conceivable to have applets in different virtual machines that talk to a server somewhere on the Internet and store any data that needs to be serialized there. Then, when another applet needs this data, it could connect to this same server. Implementing this is non-trivial.
[ Received from Krishna Kumar ]

Q: What are the steps in the JDBC connection?
A: While making a JDBC connection we go through the following steps :

Step 1 : Register the database driver by using :
Class.forName(\" driver classs for that specific database\" );
Step 2 : Now create a database connection using :
Connection con = DriverManager.getConnection(url,username,password);
Step 3: Now Create a query using :
Statement stmt = Connection.Statement(\"select * from TABLE NAME\");
Step 4 : Exceute the query :
stmt.exceuteUpdate();
[ Received from Shri Prakash Kunwar]

Q: How does a try statement determine which catch clause should be used to handle an exception?
A: When an exception is thrown within the body of a try statement, the catch clauses of the try statement are examined in the order in which they appear. The first catch clause that is capable of handling the exceptionis executed. The remaining catch clauses are ignored.
[ Received from P Rajesh]

Java Interview Questions

Question: Can an unreachable object become reachable again?

Question: What method must be implemented by all threads?

Question: What are synchronized methods and synchronized statements?

Question: What is Externalizable?

Question: What modifiers are allowed for methods in an Interface?

Question: What are some alternatives to inheritance?

Question: What does it mean that a method or field is "static"? ?

Question: What is the difference between preemptive scheduling and time slicing?

Question: What is the catch or declare rule for method declarations?

Q: Can an unreachable object become reachable again?
A: An unreachable object may become reachable again. This can happen when the object's finalize() method is invoked and the object performs an operation which causes it to become accessible to reachable objects.
[Received from P Rajesh]

Q: What method must be implemented by all threads?
A: All tasks must implement the run() method, whether they are a subclass of Thread or implement the Runnable interface.
[ Received from P Rajesh]

Q: What are synchronized methods and synchronized statements?
A: Synchronized methods are methods that are used to control access to an object. A thread only executes a synchronized method after it has acquired the lock for the method's object or class. Synchronized statements are similar to synchronized methods. A synchronized statement can only be executed after a thread has acquired the lock for the object or class referenced in the synchronized statement.
[ Received from P Rajesh]

Q: What is Externalizable?
A: Externalizable is an Interface that extends Serializable Interface. And sends data into Streams in Compressed Format. It has two methods, writeExternal(ObjectOuput out) and readExternal(ObjectInput in)
[ Received from Venkateswara Manam]

Q: What modifiers are allowed for methods in an Interface?
A: Only public and abstract modifiers are allowed for methods in interfaces.
[ Received from P Rajesh]

Q: What are some alternatives to inheritance?
A: Delegation is an alternative to inheritance. Delegation means that you include an instance of another class as an instance variable, and forward messages to the instance. It is often safer than inheritance because it forces you to think about each message you forward, because the instance is of a known class, rather than a new class, and because it doesn't force you to accept all the methods of the super class: you can provide only the methods that really make sense. On the other hand, it makes you write more code, and it is harder to re-use (because it is not a subclass).
[ Received from P Rajesh]

Q: What does it mean that a method or field is "static"?
A: Static variables and methods are instantiated only once per class. In other words they are class variables, not instance variables. If you change the value of a static variable in a particular object, the value of that variable changes for all instances of that class.
Static methods can be referenced with the name of the class rather than the name of a particular object of the class (though that works too). That's how library methods like System.out.println() work out is a static field in the java.lang.System class.
[ Received from P Rajesh]

Q: What is the difference between preemptive scheduling and time slicing?
A: Under preemptive scheduling, the highest priority task executes until it enters the waiting or dead states or a higher priority task comes into existence. Under time slicing, a task executes for a predefined slice of time and then reenters the pool of ready tasks. The scheduler then determines which task should execute next, based on priority and other factors.
[ Received from P Rajesh]

Q: What is the catch or declare rule for method declarations?
A: If a checked exception may be thrown within the body of a method, the method must either catch the exception or declare it in its throws clause.
[ Received from P Rajesh]

Java Interview Questions

Question: Is Empty .java file a valid source file?

Question: Can a .java file contain more than one java classes?

Question: Is String a primitive data type in Java?

Question: Is main a keyword in Java?

Question: Is next a keyword in Java?

Question: Is delete a keyword in Java?

Question: Is exit a keyword in Java?

Question: What happens if you dont initialize an instance variable of any of the primitive types in Java?

Question: What will be the initial value of an object reference which is defined as an instance variable?

Question: What are the different scopes for Java variables?

Question: What is the default value of the local variables?

Question: How many objects are created in the following piece of code?
MyClass c1, c2, c3;
c1 = new MyClass ();
c3 = new MyClass ();

Question: Can a public class MyClass be defined in a source file named YourClass.java?

Question: Can main method be declared final?

Question: What will be the output of the following statement?
System.out.println ("1" + 3);

Question: What will be the default values of all the elements of an array defined as an instance variable?

Q: Is Empty .java file a valid source file?
A: Yes, an empty .java file is a perfectly valid source file.
[Received from Sandesh Sadhale]

Q: Can a .java file contain more than one java classes?
A: Yes, a .java file contain more than one java classes, provided at the most one of them is a public class.
[ Received from Sandesh Sadhale]

Q: Is String a primitive data type in Java?
A: No String is not a primitive data type in Java, even though it is one of the most extensively used object. Strings in Java are instances of String class defined in java.lang package.
[ Received from Sandesh Sadhale]

Q: Is main a keyword in Java?
A: No, main is not a keyword in Java.
[ Received from Sandesh Sadhale]

Q: Is next a keyword in Java?
A: No, next is not a keyword.
[ Received from Sandesh Sadhale]

Q: Is delete a keyword in Java?
A: No, delete is not a keyword in Java. Java does not make use of explicit destructors the way C++ does.
[ Received from Sandesh Sadhale]

Q: Is exit a keyword in Java?
A: No. To exit a program explicitly you use exit method in System object.
[ Received from Sandesh Sadhale]

Q: What happens if you dont initialize an instance variable of any of the primitive types in Java?
A: Java by default initializes it to the default value for that primitive type. Thus an int will be initialized to 0, a boolean will be initialized to false.
[ Received from Sandesh Sadhale]

Q: What will be the initial value of an object reference which is defined as an instance variable?
A: The object references are all initialized to null in Java. However in order to do anything useful with these references, you must set them to a valid object, else you will get NullPointerExceptions everywhere you try to use such default initialized references.
[ Received from Sandesh Sadhale]

Q: What are the different scopes for Java variables?
A: The scope of a Java variable is determined by the context in which the variable is declared. Thus a java variable can have one of the three scopes at any given point in time.
1. Instance : - These are typical object level variables, they are initialized to default values at the time of creation of object, and remain accessible as long as the object accessible.
2. Local : - These are the variables that are defined within a method. They remain accessbile only during the course of method excecution. When the method finishes execution, these variables fall out of scope.
3. Static: - These are the class level variables. They are initialized when the class is loaded in JVM for the first time and remain there as long as the class remains loaded. They are not tied to any particular object instance.
[ Received from Sandesh Sadhale]

Q: What is the default value of the local variables?
A: The local variables are not initialized to any default value, neither primitives nor object references. If you try to use these variables without initializing them explicitly, the java compiler will not compile the code. It will complain abt the local varaible not being initilized..
[ Received from Sandesh Sadhale]

Q: How many objects are created in the following piece of code?
MyClass c1, c2, c3;
c1 = new MyClass ();
c3 = new MyClass ();
A: Only 2 objects are created, c1 and c3. The reference c2 is only declared and not initialized.
[ Received from Sandesh Sadhale]

Q: Can a public class MyClass be defined in a source file named YourClass.java?
A: No the source file name, if it contains a public class, must be the same as the public class name itself with a .java extension.
[ Received from Sandesh Sadhale]

Q: Can main method be declared final?
A: Yes, the main method can be declared final, in addition to being public static.
[ Received fromSandesh Sadhale]

Q: What will be the output of the following statement?
System.out.println ("1" + 3);
A: It will print 13.
[ Received from Sandesh Sadhale]

Q: What will be the default values of all the elements of an array defined as an instance variable?
A: If the array is an array of primitive types, then all the elements of the array will be initialized to the default value corresponding to that primitive type. e.g. All the elements of an array of int will be initialized to 0, while that of boolean type will be initialized to false. Whereas if the array is an array of references (of any type), all the elements will be initialized to null.
[ Received from Sandesh Sadhale]

Java Collection Interview Questions

Question: What is the Collections API?

Question: What is the List interface?

Question: What is the Vector class?

Question: What is an Iterator interface?

Question: Which java.util classes and interfaces support event handling?

Question: What is the GregorianCalendar class?

Question: What is the Locale class?

Question: What is the SimpleTimeZone class?

Question: What is the Map interface?

Question: What is the highest-level event class of the event-delegation model?

Question: What is the Collection interface?

Question: What is the Set interface?

Question: What is the typical use of Hashtable?

Question: I am trying to store an object using a key in a Hashtable. And some other object already exists in that location, then what will happen? The existing object will be overwritten? Or the new object will be stored elsewhere?

Question: What is the difference between the size and capacity of a Vector?

Question: Can a vector contain heterogenous objects?

Q: What is the Collections API?
A: The Collections API is a set of classes and interfaces that support operations on collections of objects.
[ Received from Prasanna Inamanamelluri]

Q: What is the List interface?
A: The List interface provides support for ordered collections of objects.
[ Received from SPrasanna Inamanamelluri]

Q: What is the Vector class?
A: The Vector class provides the capability to implement a growable array of objects.
[ Received from Prasanna Inamanamelluri]

Q: What is an Iterator interface?
A: The Iterator interface is used to step through the elements of a Collection .
[ Received from Prasanna Inamanamelluri]

Q: Which java.util classes and interfaces support event handling?
A: The EventObject class and the EventListener interface support event processing.
[ Received from Prasanna Inamanamelluri]

Q: What is the GregorianCalendar class?
A: The GregorianCalendar provides support for traditional Western calendars
[ Received from Prasanna Inamanamelluri]

Q: What is the Locale class?
A: The Locale class is used to tailor program output to the conventions of a particular geographic, political, or cultural region .
[ Received from Prasanna Inamanamelluri]

Q: What is the SimpleTimeZone class?
A: The SimpleTimeZone class provides support for a Gregorian calendar .
[ Received from Prasanna Inamanamelluri]

Q: What is the Map interface?
A: The Map interface replaces the JDK 1.1 Dictionary class and is used associate keys with values.
[ Received from Prasanna Inamanamelluri]

Q: What is the highest-level event class of the event-delegation model?
A: The java.util.EventObject class is the highest-level class in the event-delegation class hierarchy.
[ Received from Prasanna Inamanamelluri]

Q: What is the Collection interface?
A: The Collection interface provides support for the implementation of a mathematical bag - an unordered collection of objects that may contain duplicates.
[ Received from Prasanna Inamanamelluri]

Q: What is the Set interface?
A: The Set interface provides methods for accessing the elements of a finite mathematical set. Sets do not allow duplicate elements.
[ Received from Prasanna Inamanamelluri]

Q: What is the typical use of Hashtable?
A: Whenever a program wants to store a key value pair, one can use Hashtable.
[ Received from Sandesh Sadhale]

Q: I am trying to store an object using a key in a Hashtable. And some other object already exists in that location, then what will happen? The existing object will be overwritten? Or the new object will be stored elsewhere?
A: The existing object will be overwritten and thus it will be lost.
[ Received from Sandesh Sadhale]

Q: What is the difference between the size and capacity of a Vector?
A: The size is the number of elements actually stored in the vector, while capacity is the maximum number of elements it can store at a given instance of time.
[ Received from Sandesh Sadhale]

Q: Can a vector contain heterogenous objects?
A: Yes a Vector can contain heterogenous objects. Because a Vector stores everything in terms of Object.
[ Received from Sandesh Sadhale]

Q: Can a ArrayList contain heterogenous objects?
A: Yes a ArrayList can contain heterogenous objects. Because a ArrayList stores everything in terms of Object.
[ Received from Sandesh Sadhale]

Q: What is an enumeration?
A: An enumeration is an interface containing methods for accessing the underlying data structure from which the enumeration is obtained. It is a construct which collection classes return when you request a collection of all the objects stored in the collection. It allows sequential access to all the elements stored in the collection.
[ Received from Sandesh Sadhale]

Q: Considering the basic properties of Vector and ArrayList, where will you use Vector and where will you use ArrayList?
A: The basic difference between a Vector and an ArrayList is that, vector is synchronized while ArrayList is not. Thus whenever there is a possibility of multiple threads accessing the same instance, one should use Vector. While if not multiple threads are going to access the same instance then use ArrayList. Non synchronized data structure will give better performance than the synchronized one.
[ Received from Sandesh Sadhale]

Q: Can a vector contain heterogenous objects?
A: Yes a Vector can contain heterogenous objects. Because a Vector stores everything in terms of Object.
[ Received from Sandesh Sadhale]

C/C++ Algorithm for Interview

2009-02-07T16:24:00.001+05:30

1. Reverse a singly linked list

//
// iterative version
//
Node* ReverseList( Node ** List )
{

Node *temp1 = *List;
Node * temp2 = NULL;
Node * temp3 = NULL;

while ( temp1 )
{
*List = temp1; //set the head to last node
temp2= temp1->pNext; // save the next ptr in temp2
temp1->pNext = temp3; // change next to privous
temp3 = temp1;
temp1 = temp2;
}

return *List;
}

2. Delete a node in double linked list

void deleteNode(node *n)
{
node *np = n->prev;
node *nn = n->next;
np->next = n->next;
nn->prev = n->prev;
delete n;
}

3. Sort a linked list

//sorting in descending order
struct node
{
int value;
node* NEXT;
}
//Assume HEAD pointer denotes the first element in the //linked list
// only change the values…don’t have to change the //pointers

Sort( Node *Head)
{
node* first,second,temp;
first= Head;
while(first!=null)
{
second=first->NEXT;
while(second!=null)
{
if(first->value < second->value)
{
temp = new node();
temp->value=first->value;
first->value=second->value;
second->value=temp->value;
delete temp;
}
second=second->NEXT;
}

first=first->NEXT;
}
}

4. Reverse a string

void ReverseString (char *String)
{
char *Begin = String;
char *End = String + strlen(String) - 1;
char TempChar = '\0';

while (Begin < End)
{
TempChar = *Begin;
*Begin = *End;
*End = TempChar;
Begin++;
End--;
}
}

5. Insert a node a sorted linked list

void sortedInsert(Node * head, Node* newNode)
{
Node *current = head;

// traverse the list until you find item bigger the // new node value
//
while (current!= NULL && current->data < newNode->data)
{
current = current->next);
}
//
// insert the new node before the big item
//
newNode->next = current->next;
current = newNode;
}

6. Covert a string to upper case

void ToUpper(char * S)
{
while (*S!=0)
{
*S=(*S >= 'a' && *S <= 'z')?(*S-'a'+'A'):*S;
S++;
}
}

7. Multiple a number by 7 without using * and + operator.

NewNum = Num << 3; // mulitplied by 2 ^ 3 = 8

NewNum = NewNum - Num; // 8 – 1 = 7

8. Write a function that takes in a string parameter and checks to see whether or not it is an integer, and if it is then return the integer value.

#include

int strtoint(char *s)
{
int index = 0, flag = 0;

while( *(s+index) != '\0')
{
if( (*(s + index) >= '0') &&
*(s + index) <= '9')
{
flag = 1;
index++;
}
else
{
flag = 0;
break;
}
}

if( flag == 1 )
return atoi(s);
else
return 0;
}

main()
{
printf("%d",strtoint("0123"));
printf("\n%d",strtoint("0123ii"));
}

9. Print a data from a binary tree – In-order(ascending)

//
// recursive version
//

Void PrintTree ( struct * node node )
{
if ( node == NULL )
return;

PrintTree(node->left );
Printf(“%d”, node->data);
PrintTree(node->right );
}

10. print integer using only putchar

//
// recursive version
//
void PrintNum ( int Num )
{
if ( Num == 0 )
return;
PrintNum ( Num / 10 );
Puthcar ( ‘0’+ Num % 10 );
}

11. Find the factorial of number

//
// recursive version
//

int Factorial( int Num )
{

If ( num > 0 )
return Num * Factorial ( Num –1 );
else
return 1;
}

//
// iterative version
//

int Factorial( int Num )
{
int I
int result = 1;

for ( I= Num; I > 0; I-- )
{
result = result * I;
}

return result;
}

12. Generate Fib numbers:

int fib( n ) // recursive version
{

if ( n < 2 )
return 1;
else
return fib ( n –1 ) + fib ( n –2 );

}

int fib( n ) //iterative version
{
int f1 =1, f2 = 1;

if ( n < 2 )
return 1;
for ( i = 1; i < N; i++)
{
f = f1 + f2;
f1= f2;
f = f1;
}

return f;
}

13. Write a function that finds the last instance of a character in a string

char *lastchar(char *String, char ch)
{
char *pStr = NULL;

// traverse the entire string

while( * String ++ != NULL )
{
if( *String == ch )
pStr = String;
}

return pStr;
}

14. Return Nth the node from the end of the linked list in one pass.

Node * GetNthNode ( Node* Head , int NthNode )
{
Node * pNthNode = NULL;
Node * pTempNode = NULL;
int nCurrentElement = 0;

for ( pTempNode = Head; pTempNode != NULL; pTempNode = pTempNode->pNext )
{
nCurrentElement++;
if ( nCurrentElement - NthNode == 0 )
{
pNthNode = Head;
}
else
if ( nCurrentElement - NthNode > 0)
{
pNthNode = pNthNode ->pNext;
}
}
if (pNthNode )
{
return pNthNode;
}
else
return NULL;
}

15. Counting set bits in a number.

First version:

int CoutSetBits(int Num)
{

for(int count=0; Num; Num >>= 1)
{
if (Num & 1)
count++;
}
return count;
}

Optimized version:

int CoutSetBits(int Num)
{

for(int count =0; Num; count++)
{
Num &= Num -1;
}
}

DBMS Interview Question and Answer

2009-02-07T16:22:00.000+05:30

DBMS Interview Questions and Answers
QUESTION 1:
What is database?
ANSWER:
A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.
QUESTION 2:
What is DBMS?
ANSWER:
• Redundancy is controlled.
• Unauthorised access is restricted.
• Providing multiple user interfaces.
• Enforcing integrity constraints.
• Providing backup and recovery.
QUESTION 4:
What is a Database system?
ANSWER:
The database and DBMS software together is called as Database system.
QUESTION 5:
Disadvantage in File Processing System?
ANSWER:
• Data redundancy & inconsistency.
• Difficult in accessing data.
• Data isolation.
• Data integrity.
• Concurrent access is not possible.
• Security Problems. .
QUESTION 6:
Describe the three levels of data abstraction?
ANSWER:
The are three levels of abstraction:
• Physical level: The lowest level of abstraction describes how data are stored.
• Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
• View level: The highest level of abstraction describes only part of entire database.
QUESTION 7:
Define the "integrity rules"
ANSWER:
There are two Integrity rules.
• Entity Integrity: States that “Primary key cannot have NULL value”
• Referential Integrity: States that “Foreign Key can be either a NULL value or should be Primary Key value of other relation.
QUESTION 8:
What is extension and intension?
ANSWER:
Extension -It is the number of tuples present in a table at any instance. This is time dependent.
Intension - It is a constant value that gives the name, structure of table and the constraints laid on it.
QUESTION 9:
What is System R? What are its two major subsystems?
ANSWER:
System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center . It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system.
Its two subsystems are
• Research Storage
• System Relational Data System.
QUESTION 10:
How is the data structure of System R different from the relational structure?
ANSWER:
Unlike Relational systems in System R
• Domains are not supported
• Enforcement of candidate key uniqueness is optional
• Enforcement of entity integrity is optional
• Referential integrity is not enforced
QUESTION 11:
What is Data Independence?
ANSWER:
Data independence means that “the application is independent of the storage structure and access strategy of data”. In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
• Physical Data Independence : Modification in physical level should not affect the logical level.
• Logical Data Independence : Modification in logical level should affect the view level.
NOTE: Logical Data Independence is more difficult to achieve
QUESTION 12:
What is a view? How it is related to data independence?
ANSWER:
A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence. .
QUESTION 13:
What is Data Model?
ANSWER:
A collection of conceptual tools for describing data, data relationships data semantics and constraints.
QUESTION 14:
What is E-R model?
ANSWER:
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.
QUESTION 15:
What is Object Oriented model?
ANSWER:
This model is based on collection of objects. An object contains values stored in instance variables with in the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.
QUESTION 16:
What is an Entity?
ANSWER:
It is a 'thing' in the real world with an independent existence.
QUESTION 17:
What is an Entity type?
ANSWER:
It is a collection (set) of entities that have same attributes.
QUESTION 18:
What is an Entity set?
ANSWER:
It is a collection of all entities of particular entity type in the database.
QUESTION 19:
What is an Extension of entity type?
ANSWER:
The collections of entities of a particular entity type are grouped together into an entity set.
QUESTION 20:
What is Weak Entity set?
ANSWER:
An entity set may not have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its parent entity, then it is said to be Weak Entity set.
QUESTION 21:
What is an attribute?
ANSWER:
It is a particular property, which describes the entity.
QUESTION 22:
What is a Relation Schema and a Relation?
ANSWER:
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).
QUESTION 23:
What is degree of a Relation?
ANSWER:
It is the number of attribute of its relation schema.
QUESTION 24:
What is Relationship?
ANSWER:
It is an association among two or more entities.
QUESTION 25:
What is Relationship set?
ANSWER:
The collection (or set) of similar relationships.
QUESTION 26:
What is Relationship type?
ANSWER:
Relationship type defines a set of associations or a relationship set among a given set of entity types.
QUESTION 27:
What is degree of Relationship type?
ANSWER:
It is the number of entity type participating.
QUESTION 28:
What is Data Storage - Definition Language?
ANSWER:
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.
QUESTION 29:
What is DML (Data Manipulation Language)?
ANSWER:
This language that enable user to access or manipulate data as organised by appropriate data model.
• Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
• Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.
QUESTION 30:
What is VDL (View Definition Language)?
ANSWER:
It specifies user views and their mappings to the conceptual schema.
QUESTION 31:
What is DML Compiler?
ANSWER:
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.
QUESTION 32:
What is Query evaluation engine?
ANSWER:
It executes low-level instruction generated by compiler.
QUESTION 33:
What is DDL Interpreter?
ANSWER:
It interprets DDL statements and record them in tables containing metadata.
QUESTION 34:
What is Record-at-a-time?
ANSWER:
The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.
QUESTION 35:
What is Set-at-a-time or Set-oriented?
ANSWER:
The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.
QUESTION 36:
What is Relational Algebra?
ANSWER:
It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.
QUESTION 37:
What is Relational Calculus?
ANSWER:
It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.
QUESTION 38:
How does Tuple-oriented relational calculus differ from domain-oriented relational calculus
ANSWER:
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL
The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.
QUESTION 39:
What is normalization?
ANSWER:
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
• Minimizing redundancy
• Minimizing insertion, deletion and update anomalies.
QUESTION 40:
What is Functional Dependency?
ANSWER:
A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.
QUESTION 41:
When is a functional dependency F said to be minimal?
ANSWER:
• Every dependency in F has a single attribute for its right hand side.
• We cannot replace any dependency X A in F with a dependency Y A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
• We cannot remove any dependency from F and still have set of dependency that is equivalent to F.
QUESTION 42:
What is Multivalued dependency?
ANSWER:
Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties
• t3[x] = t4[X] = t1[X] = t2[X]
• t3[Y] = t1[Y] and t4[Y] = t2[Y]
• t3[Z] = t2[Z] and t4[Z] = t1[Z]
where [Z = (R-(X U Y)) ]
QUESTION 43:
What is Lossless join property?
ANSWER:
It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.
QUESTION 44:
What is 1 NF (Normal Form)?
ANSWER:
The domain of attribute must include only atomic (simple, indivisible) values.
QUESTION 45:
What is Fully Functional dependency?
ANSWER:
It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.
QUESTION 46:
What is 2NF?
ANSWER:
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.
QUESTION 47:
What is 3NF?
ANSWER:
A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
• X is a Super-key of R.
• A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.
QUESTION 48:
What is BCNF (Boyce-Codd Normal Form)?
ANSWER:
A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X A, X must be a candidate key.
QUESTION 49:
What is 4NF?
ANSWER:
A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true
• X is subset or equal to (or) XY = R.
• X is a super key.
QUESTION 50:
What is 5NF?
ANSWER:
A Relation schema R is said to be 5NF if for every join dependency {R1, R2, ..., Rn} that holds R, one the following is true
• Ri = R for some i.
• The join dependency is implied by the set of FD, over R in which the left side is key of R.

DATA BASE MANAGEMENT SYSTEM

2009-02-07T16:21:00.000+05:30

1. What is database?
A database is a logically coherent collection of data with some inherent meaning, representing some aspect of real world and which is designed, built and populated with data for a specific purpose.

2. What is DBMS?
It is a collection of programs that enables user to create and maintain a database. In other words it is general-purpose software that provides the users with the processes of defining, constructing and manipulating the database for various applications.

3. What is a Database system?
The database and DBMS software together is called as Database system.

4. Advantages of DBMS?
Ø Redundancy is controlled.
Ø Unauthorised access is restricted.
Ø Providing multiple user interfaces.
Ø Enforcing integrity constraints.
Ø Providing backup and recovery.

5. Disadvantage in File Processing System?
Ø Data redundancy & inconsistency.
Ø Difficult in accessing data.
Ø Data isolation.
Ø Data integrity.
Ø Concurrent access is not possible.
Ø Security Problems.

6. Describe the three levels of data abstraction?
The are three levels of abstraction:
Ø Physical level: The lowest level of abstraction describes how data are stored.
Ø Logical level: The next higher level of abstraction, describes what data are stored in database and what relationship among those data.
Ø View level: The highest level of abstraction describes only part of entire database.
7. Define the "integrity rules"
There are two Integrity rules.
Ø Entity Integrity: States that "Primary key cannot have NULL value"
Ø Referential Integrity: States that "Foreign Key can be either a NULL value or should be Primary Key value of other relation.

8. What is extension and intension?
Extension -
It is the number of tuples present in a table at any instance. This is time dependent.
Intension -
It is a constant value that gives the name, structure of table and the constraints laid on it.

9. What is System R? What are its two major subsystems?
System R was designed and developed over a period of 1974-79 at IBM San Jose Research Center. It is a prototype and its purpose was to demonstrate that it is possible to build a Relational System that can be used in a real life environment to solve real life problems, with performance at least comparable to that of existing system.
Its two subsystems are
Ø Research Storage
Ø System Relational Data System.

10. How is the data structure of System R different from the relational structure?
Unlike Relational systems in System R
Ø Domains are not supported
Ø Enforcement of candidate key uniqueness is optional
Ø Enforcement of entity integrity is optional
Ø Referential integrity is not enforced

11. What is Data Independence?
Data independence means that "the application is independent of the storage structure and access strategy of data". In other words, The ability to modify the schema definition in one level should not affect the schema definition in the next higher level.
Two types of Data Independence:
Ø Physical Data Independence: Modification in physical level should not affect the logical level.
Ø Logical Data Independence: Modification in logical level should affect the view level.
NOTE: Logical Data Independence is more difficult to achieve
12. What is a view? How it is related to data independence?
A view may be thought of as a virtual table, that is, a table that does not really exist in its own right but is instead derived from one or more underlying base table. In other words, there is no stored file that direct represents the view instead a definition of view is stored in data dictionary.
Growth and restructuring of base tables is not reflected in views. Thus the view can insulate users from the effects of restructuring and growth in the database. Hence accounts for logical data independence.

13. What is Data Model?
A collection of conceptual tools for describing data, data relationships data semantics and constraints.

14. What is E-R model?
This data model is based on real world that consists of basic objects called entities and of relationship among these objects. Entities are described in a database by a set of attributes.

15. What is Object Oriented model?
This model is based on collection of objects. An object contains values stored in instance variables with in the object. An object also contains bodies of code that operate on the object. These bodies of code are called methods. Objects that contain same types of values and the same methods are grouped together into classes.

16. What is an Entity?
It is a 'thing' in the real world with an independent existence.

17. What is an Entity type?
It is a collection (set) of entities that have same attributes.

18. What is an Entity set?
It is a collection of all entities of particular entity type in the database.

19. What is an Extension of entity type?
The collections of entities of a particular entity type are grouped together into an entity set.
20. What is Weak Entity set?
An entity set may not have sufficient attributes to form a primary key, and its primary key compromises of its partial key and primary key of its parent entity, then it is said to be Weak Entity set.

21. What is an attribute?
It is a particular property, which describes the entity.

22. What is a Relation Schema and a Relation?
A relation Schema denoted by R(A1, A2, …, An) is made up of the relation name R and the list of attributes Ai that it contains. A relation is defined as a set of tuples. Let r be the relation which contains set tuples (t1, t2, t3, ..., tn). Each tuple is an ordered list of n-values t=(v1,v2, ..., vn).

23. What is degree of a Relation?
It is the number of attribute of its relation schema.

24. What is Relationship?
It is an association among two or more entities.

25. What is Relationship set?
The collection (or set) of similar relationships.

26. What is Relationship type?
Relationship type defines a set of associations or a relationship set among a given set of entity types.

27. What is degree of Relationship type?
It is the number of entity type participating.

25. What is DDL (Data Definition Language)?
A data base schema is specifies by a set of definitions expressed by a special language called DDL.

26. What is VDL (View Definition Language)?
It specifies user views and their mappings to the conceptual schema
27. What is SDL (Storage Definition Language)?
This language is to specify the internal schema. This language may specify the mapping between two schemas.

28. What is Data Storage - Definition Language?
The storage structures and access methods used by database system are specified by a set of definition in a special type of DDL called data storage-definition language.

29. What is DML (Data Manipulation Language)?
This language that enable user to access or manipulate data as organised by appropriate data model.
Ø Procedural DML or Low level: DML requires a user to specify what data are needed and how to get those data.
Ø Non-Procedural DML or High level: DML requires a user to specify what data are needed without specifying how to get those data.

31. What is DML Compiler?
It translates DML statements in a query language into low-level instruction that the query evaluation engine can understand.

32. What is Query evaluation engine?
It executes low-level instruction generated by compiler.

33. What is DDL Interpreter?
It interprets DDL statements and record them in tables containing metadata.

34. What is Record-at-a-time?
The Low level or Procedural DML can specify and retrieve each record from a set of records. This retrieve of a record is said to be Record-at-a-time.

35. What is Set-at-a-time or Set-oriented?
The High level or Non-procedural DML can specify and retrieve many records in a single DML statement. This retrieve of a record is said to be Set-at-a-time or Set-oriented.

36. What is Relational Algebra?
It is procedural query language. It consists of a set of operations that take one or two relations as input and produce a new relation.
37. What is Relational Calculus?
It is an applied predicate calculus specifically tailored for relational databases proposed by E.F. Codd. E.g. of languages based on it are DSL ALPHA, QUEL.

38. How does Tuple-oriented relational calculus differ from domain-oriented relational calculus
The tuple-oriented calculus uses a tuple variables i.e., variable whose only permitted values are tuples of that relation. E.g. QUEL
The domain-oriented calculus has domain variables i.e., variables that range over the underlying domains instead of over relation. E.g. ILL, DEDUCE.

39. What is normalization?
It is a process of analysing the given relation schemas based on their Functional Dependencies (FDs) and primary key to achieve the properties
Ø Minimizing redundancy
Ø Minimizing insertion, deletion and update anomalies.

40. What is Functional Dependency?
A Functional dependency is denoted by X Y between two sets of attributes X and Y that are subsets of R specifies a constraint on the possible tuple that can form a relation state r of R. The constraint is for any two tuples t1 and t2 in r if t1[X] = t2[X] then they have t1[Y] = t2[Y]. This means the value of X component of a tuple uniquely determines the value of component Y.

41. When is a functional dependency F said to be minimal?
Ø Every dependency in F has a single attribute for its right hand side.
Ø We cannot replace any dependency X A in F with a dependency Y A where Y is a proper subset of X and still have a set of dependency that is equivalent to F.
Ø We cannot remove any dependency from F and still have set of dependency that is equivalent to F.

42. What is Multivalued dependency?
Multivalued dependency denoted by X Y specified on relation schema R, where X and Y are both subsets of R, specifies the following constraint on any relation r of R: if two tuples t1 and t2 exist in r such that t1[X] = t2[X] then t3 and t4 should also exist in r with the following properties
Ø t3[x] = t4[X] = t1[X] = t2[X]
Ø t3[Y] = t1[Y] and t4[Y] = t2[Y]
Ø t3[Z] = t2[Z] and t4[Z] = t1[Z]
where [Z = (R-(X U Y)) ]
43. What is Lossless join property?
It guarantees that the spurious tuple generation does not occur with respect to relation schemas after decomposition.

44. What is 1 NF (Normal Form)?
The domain of attribute must include only atomic (simple, indivisible) values.

45. What is Fully Functional dependency?
It is based on concept of full functional dependency. A functional dependency X Y is full functional dependency if removal of any attribute A from X means that the dependency does not hold any more.

46. What is 2NF?
A relation schema R is in 2NF if it is in 1NF and every non-prime attribute A in R is fully functionally dependent on primary key.

47. What is 3NF?
A relation schema R is in 3NF if it is in 2NF and for every FD X A either of the following is true
Ø X is a Super-key of R.
Ø A is a prime attribute of R.
In other words, if every non prime attribute is non-transitively dependent on primary key.

48. What is BCNF (Boyce-Codd Normal Form)?
A relation schema R is in BCNF if it is in 3NF and satisfies an additional constraint that for every FD X A, X must be a candidate key.

49. What is 4NF?
A relation schema R is said to be in 4NF if for every Multivalued dependency X Y that holds over R, one of following is true
Ø X is subset or equal to (or) XY = R.
Ø X is a super key.

50. What is 5NF?
A Relation schema R is said to be 5NF if for every join dependency {R1, R2, ..., Rn} that holds R, one the following is true
Ø Ri = R for some i.
Ø The join dependency is implied by the set of FD, over R in which the left side is key of R.
51. What is Domain-Key Normal Form?
A relation is said to be in DKNF if all constraints and dependencies that should hold on the the constraint can be enforced by simply enforcing the domain constraint and key constraint on the relation.

52. What are partial, alternate,, artificial, compound and natural key?
Partial Key:
It is a set of attributes that can uniquely identify weak entities and that are related to same owner entity. It is sometime called as Discriminator.
Alternate Key:
All Candidate Keys excluding the Primary Key are known as Alternate Keys.
Artificial Key:
If no obvious key, either stand alone or compound is available, then the last resort is to simply create a key, by assigning a unique number to each record or occurrence. Then this is known as developing an artificial key.
Compound Key:
If no single data element uniquely identifies occurrences within a construct, then combining multiple elements to create a unique identifier for the construct is known as creating a compound key.
Natural Key:
When one of the data elements stored within a construct is utilized as the primary key, then it is called the natural key.

53. What is indexing and what are the different kinds of indexing?
Indexing is a technique for determining how quickly specific data can be found.
Types:
Ø Binary search style indexing
Ø B-Tree indexing
Ø Inverted list indexing
Ø Memory resident table
Ø Table indexing

54. What is system catalog or catalog relation? How is better known as?
A RDBMS maintains a description of all the data that it contains, information about every relation and index that it contains. This information is stored in a collection of relations maintained by the system called metadata. It is also called data dictionary.
55. What is meant by query optimization?
The phase that identifies an efficient execution plan for evaluating a query that has the least estimated cost is referred to as query optimization.

56. What is join dependency and inclusion dependency?
Join Dependency:
A Join dependency is generalization of Multivalued dependency.A JD {R1, R2, ..., Rn} is said to hold over a relation R if R1, R2, R3, ..., Rn is a lossless-join decomposition of R . There is no set of sound and complete inference rules for JD.
Inclusion Dependency:
An Inclusion Dependency is a statement of the form that some columns of a relation are contained in other columns. A foreign key constraint is an example of inclusion dependency.

57. What is durability in DBMS?
Once the DBMS informs the user that a transaction has successfully completed, its effects should persist even if the system crashes before all its changes are reflected on disk. This property is called durability.

58. What do you mean by atomicity and aggregation?
Atomicity:
Either all actions are carried out or none are. Users should not have to worry about the effect of incomplete transactions. DBMS ensures this by undoing the actions of incomplete transactions.
Aggregation:
A concept which is used to model a relationship between a collection of entities and relationships. It is used when we need to express a relationship among relationships.

59. What is a Phantom Deadlock?
In distributed deadlock detection, the delay in propagating local information might cause the deadlock detection algorithms to identify deadlocks that do not really exist. Such situations are called phantom deadlocks and they lead to unnecessary aborts.

60. What is a checkpoint and When does it occur?
A Checkpoint is like a snapshot of the DBMS state. By taking checkpoints, the DBMS can reduce the amount of work to be done during restart in the event of subsequent crashes.61. What are the different phases of transaction?
Different phases are
Ø Analysis phase
Ø Redo Phase
Ø Undo phase

62. What do you mean by flat file database?
It is a database in which there are no programs or user access languages. It has no cross-file capabilities but is user-friendly and provides user-interface management.

63. What is "transparent DBMS"?
It is one, which keeps its Physical Structure hidden from user.

64. Brief theory of Network, Hierarchical schemas and their properties
Network schema uses a graph data structure to organize records example for such a database management system is CTCG while a hierarchical schema uses a tree data structure example for such a system is IMS.

65. What is a query?
A query with respect to DBMS relates to user commands that are used to interact with a data base. The query language can be classified into data definition language and data manipulation language.

66. What do you mean by Correlated subquery?
Subqueries, or nested queries, are used to bring back a set of rows to be used by the parent query. Depending on how the subquery is written, it can be executed once for the parent query or it can be executed once for each row returned by the parent query. If the subquery is executed for each row of the parent, this is called a correlated subquery.
A correlated subquery can be easily identified if it contains any references to the parent subquery columns in its WHERE clause. Columns from the subquery cannot be referenced anywhere else in the parent query. The following example demonstrates a non-correlated subquery.
E.g. Select * From CUST Where '10/03/1990' IN (Select ODATE From ORDER Where CUST.CNUM = ORDER.CNUM)

67. What are the primitive operations common to all record management systems?
Addition, deletion and modification.

Computer Abbreviations Dictionary

2009-02-07T16:19:00.000+05:30

Computer Abbreviations Dictionary
• ACE - Access Control Entry
• ACL - Access Control List
• ADO - Active Data Objects
• AGP - Accelerated Graphics Port
• AI - Artificial Intelligence
• ALGOL - Algorithmic Language
• ALU - Arithmetic Logic Unit
• AOL - America Online
• API - Application Program Interface
• APIPA - Automatic Private Internet Protocol Addressing
• ARP - Address Resolution Protocol
• ASCII - American Standard Code for Information Interchange
• ASF - Advanced Streaming Format
• ASM - Association for Systems Management
• ASP - Active Server Pages
• ATAPI - Advanced Technology Attachment Packet Interface
• ATM - Asynchronous Transfer Mode
• AUI - Attachment Unit Interface
• AVI - Audio Video Interleave
• B2B - Business to Business
• B2C - Business to Commerce
• BASIC - Beginner's All Purpose Symbolic Instruction Code
• BCD - Binary Coded Decimal
• BHTML - Broadcast Hyper Text Markup Language
• BIOS - Basic Input Output System
• BMP - Bitmap
• CAD - Computer Aided Design
• CAI - Computer Aided Instructuion
• CAM - Computer Aided Manufacturing
• CASE - Computer Aided Software Engineering
• CCNA - Cisco Certified Network Associate
• CD - Compact Disc
• CD - RW - Compact Disc Re-Writable
• CD - WORM - Compact Disc - Write Once Read Many
• C-DAC - Centre for Development of Advanced Computing
• CDONTS - Collabaration on Data Objects for Windows NT Server
• CGI - Common Gateway Interface
• CIDR - Classless Inter-Domain Routing
• CLR - Common Language Runtime
• CMOS - Complementary Metal Oxide Semiconductor
• CMS - Content Management System
• CMYK - Cyan, Magenta, Yellow, Key (black)
• COBOL - Common Business Oriented Language
• COM - Component Object Model
• CORBA - Common Object Request Broker Architecture
• CPU - Central Processing Unit
• CRC - Cyclic Redundancy Check
• CRM - Customer Relationship Management
• CROM - Control Read Only Memory
• CRT - Cathode Ray Tube
• CUI - Character User Interface
• DAC - Digital to Analog Converter
• DAO - Data Access Objects
• DAT - Digital Audio Tape
• DBA - Data Base Administrator
• DBMS - Data Base Management System
• DCOM - Distributed Component Object Model
• DDL - Data Definition Language
• DFS - Distributed File System
• DHCP - Domain Host Configuration Protocol
• DHTML - Dynamics Hyper Text Markup Language
• DLC - Data Link Control
• dll - dynamic link library
• DMA - Direct Memory Access
• DML - Data Manipulation Language
• DNS - Domain Name System
• DOM - Document Object Model
• DOS - Disk Operating System, Denial Of Service
• DDOS - Distributed Denial Of Service
• dpi - dots per inch
• DSL - Digital Subscriber Line
• DSN - Digital Subscriber Network
• DTD - Document Type Definition
• DVD - Digital Versatile Disc
• e - electronic
• EBCDIC - Extended Binary Coded Decimal Interchange Code
• EFS - Encrypted File System
• EPROM - Erasable Programmable Read Only Memory
• EEPROM - Electrically Erasable Programmable Read Only Memory
• EJB - Enterprise Java Beans
• ERP - Enterprise Resource Planning
• EULA - End User License Agreement
• FAT - File Allocation Table
• FDD- Floppy Disk Drive
• FDDI - Fiber Distributed Data Interface
• FIFO - First In First Out
• FLOPS - Floating Point Operations Per Second
• FO - Fiber Optics
• FORTRAN - FORmula TRANslation
• fps - frames per second
• FRAM - Ferro-electric Random Access Memory
• GB - Giga Bytes
• GIF - Graphic Interchange Format
• GIGO - Garbage In Garbage Out
• GNU - GNU's Not Unix
• GPL - General Public License
• GUI - Graphical User Interface
• HDD - Hard Disk Drive
• HFS - Hierarchical File System
• HP - Hewlett Packard
• HPC - High Performance Computing
• HPFS - High Performance File System
• HSR - Horizontal Scan Rate
• HTML - Hyper Text Markup Language
• HTTP - Hyper Text Transfer Protocol
• hw - Hardware
• IBM - International Business Machines
• ICMP - Internet Control Message Protocol
• IDE - Integrated Development Environment
• IGMP - Internet Group Management Protocol
• IIS - Internet Information Server
• IL - Intermediate Language
• I/O - Input Output
• IP - Internet Protocol
• IPX - Internetworked Packet Exchange
• IrDA - Infrared Data Association
• IRQ - Interrupt Request
• ISAPI - Internet Server Application Program Interface
• ISDN - Integrated Services Digital Network
• ISP - Internet Service Provider
• IT - Information Technology
• ITPL - Information Technology Park Limited (India)
• JCL - Job Control Language
• JDBC - Java Data Base Connectivity
• JHTML - Java within Hyper Text Markup Language
• JPEG - Joint Photographic Experts Group
• JSP - Java Server Pages
• kb - kilobytes
• kbps - Kilo bytes per second
• L2TP - Layer Two Tunneling Protocol
• LAN - Local Area Network
• LCD - Liquid Crystal Display
• LIFO - Last In First Out
• LIPS - Logical Interfaces Per Second
• LOC - Lines Of Code
• LSP - Layered Service Provider
• MB - Mega Bytes
• MBPS - Mega Bytes Per Second
• MBR - Master Boot Record
• MAC - Media Access Control
• MAN - Metropolitan Area Network
• MAU - Multi-station Access Unit
• MCP - Microsoft Certified Professional
• MCS - MultiCast Server
• MCSA - Microsoft® Certified Systems Administrator
• MCSD - Microsoft® Certified Solution Developer
• MCSE - Microsoft® Certified System Engineer
• MDI - Multiple Document Interface
• MFC - Microsoft Foundation Classes
• MFT - Master File Table
• MIDI - Musical Instrument Digital Interface
• MIMD - Multiple Instruction Multiple Data
• MIME - Multipurpose Internet Mail Extensions
• MISD - Multiple Instruction Single Data
• MIPS - Millions of Instructions Per Second
• MODEM - MOdulator and DEModulator
• MP3 - Motion Pictures Experts Group Layer - 3
• MPEG - Motion Pictures Experts Group
• MS - MicroSoft
• MSDN - MicroSoft Developer Network
• MSIL - Microsoft Intermediate Language
• MSIIS - MicroSoft Internet Information Server
• MSN - MicroSoft Network
• MSRAP - MicroSoft Remote Administration Protocol
• MSRPC - Microsoft Remote Procedure Call
• MTS - Microsoft Transaction Server
• MTU - Maximum Transmission Unit
• NASSCOM - National Association of Software & Service Companies
• NDIS - Network Driver Interface Specification
• NetBEUI - NetBIOS Enhanced User Interface
• NIC - National Informatics Centre,
• NIIT - National Institute of Information Technology
• NNTP - Network News Transfer Protocol
• NOW - Network Of Workstations
• NT (Windows) - New Technology
• NTP - Network Time Protocol
• NTFS - New Technology File System
• OCP - Oracle Certified Professional
• ODBC - Open Data Base Connectivity
• OLE - Object Linking and Embedding
• OMR - Optical Mark Reader
• ONE - Open Network Architecture
• OOAD - Object Oriented Analysis and Design
• OOPS - Object Oriented Programming System
• Open GL - Open Graphics Library
• OS - Operating System
• PC - Personal Computer
• PCI - Peripheral Component Interconnect
• PCMCIA - Personal Computer Memory Card International Association
• PDA - Personal Digital Assistant
• PDF - Portable Document Format
• PDL - Page Description Language
• PHP - PHP Hypertext Processor
• PLC - Programmable Logic Controller
• PNG - Portable Network Graphics
• PnP - Plug and Play
• POP - Post Office Protocol
• POST - Power On Self Test
• PPP - Peer to Peer Protocol
• PPTP - Point to Point Tunneling Protocol
• PROM - Programmable Read Only Memory
• PS - Post Script
• PSN - Processor Serial Number
• QoS - Quality of Service
• RAID - Redundant Array of Independent Disks
• RAM - Random Access Memory
• RAMDAC - Random Access Memory Digital to Analog Converter
• RDBMS - Relational Data Base Management System
• RDO - Remote Data Objects
• RDP - Remote Desktop Protocol
• RD RAM - Rambus Dynamic Random Access Memory
• R-DAT - Rotating Digital Audio Tape
• RFC - Request For Comments
• RGB - Red Green Blue
• RIP - Raster Image Processor
• RISC - Reduced Instruction Set Computer
• ROM - Read Only Memory
• RPC - Remote Procedure Call
• RTC - Real Time Clock
• RTF - Rich Text Format
• RTOS - Real Time Operating System
• SACK - Selective Acknowledgements
• SAM - Security Access Manager
• SAP - Service Access Point, Systems Applications Products
• SCSI - Small Computers Systems Interface
• SRAM - Static Random Access Memory
• SD RAM - Synchronous Dynamic Random Access Memory
• S - DAT - Stationary Digital Audio Tape
• SDK - Software Development Kit
• SGML - Standard Generalized Markup Language
• SG RAM - Synchronous Graphics Random Access Memory
• SIM - Subscriber Identification Module
• SIMD - Single Instruction Multiple Data
• SISD - Single Instruction Single Data
• SMS - Short Message Service
• SMTP - Simple Mail Transfer Protocol
• SNA - System Network Architecture
• SNAP - Sub Network Access Protocol
• SNMP - Simple Network Management Protocol
• SOAP - Simple Object Access Protocol
• SPX - Sequenced Packet Exchange
• SQL - Structured Query Language
• sw - software
• TB - Tera Bytes
• TAPI - Telephony Application Program Interface
• TCP - Transmission Control Protocol
• TCP/IP - Transmission Control Protocol / Internet Protocol
• TDI - Transport Data Interface
• TPM - Transactions Processing Monitor
• TSR - Terminate and Stay Residents
• UDP - User Datagram Protocol
• UNC - Universal Naming Convention
• UNIX - Uniplexed Information and Computer Systems
• UML - Unified Modelling Language
• URL - Universal Resource Locator
• USB - Universal Serial Bus
• UTP - Unshielded Twisted Pair
• VAN - Virtual Area Network
• VB - Visual Basic
• VC++ - Visual C++
• VCD - Video Compact Disc
• VGA - Video Graphics Array
• VHS - Video Home System
• VLIW - Very Long Instruction Words
• VLSI - Very Large Scale Integrated Circuits
• VPN - Virtual Private Network
• VRAM - Video Random Access Memory
• VRML - Virtual Reality Modelling Language
• VS - Visual Studio
• VSNL - Videsh Sanchar Nigam Limited
• VXD - Virtual Device Driver

• W3C - World Wide Web Consortium
• WAN - Wide Area Network
• WAP - Wireless Application Protocol
• WHQL - Windows Hardware Quality Lab
• Windows ME - Windows Millennium Edition
• Windows NT - Windows New Technology
• Windows XP - Windows eXPerienced
• WINS - Windows Internet Name Services
• WMI - Windows Management Instrumentation
• WML - Wireless Markup Language
• WORM - Write Once Read Many
• WYSIWYG - What You See Is What You Get
• WWW - World Wide Web
• XHTML - eXtensible Hyper Text Markup Language
• XML - eXtensible Markup Language
• XSL - eXtensible Style Sheet langauge
• Y2K - Year 2000
• ZIF - Zero Insertion Force

What is FLASH?

2009-02-07T16:17:00.000+05:30

What is Flash?
• Macromedia Flash is a multimedia graphics program specially for use on the Web
• Flash enables you to create interactive "movies" on the Web
• Flash uses vector graphics, which means that the graphics can be scaled to any size without losing clarity/quality
• Flash does not require programming skills and is easy to learn
________________________________________
Flash vs. Animated Images and Java Applets
Animated images and Java applets are often used to create dynamic effects on Web pages.
The advantages of Flash are:
• Flash loads much faster than animated images
• Flash allows interactivity, animated images do not
• Flash does not require programming skills, java applets do
Flash Embedded in HTML
After creating a Flash movie you choose File > Save As from the top menu to save your movie. Save the file as "Somefilename.fla".
To embed the Flash movie you just made into an HTML page, you should go back to your Flash program and do the following steps:
Step 1
Choose File > Open. Open a Flash movie you have created.
Step 2
Choose File > Export Movie.
Step 3
Name the file "somefilename.swf". Choose the location where the file is to be stored (in your Web folder). Click OK.
Step 4
Open the HTML page where you want to insert your Flash movie. Insert this code:

Note: This is the minimum code you need to embed a Flash movie in a browser. A broken icon will appear on the Web page if the user does not have the Flash plug-in installed.
Note: In the code above there is both an tag and an tag. This is because the tag is recognized by Internet Explorer, and Netscape recognizes the tag and ignores the tag.
Step 5
Type in the address of the HTML file in your browser and look at your first Flash movie.
________________________________________
Let the Flash Program do the Work
The code above is the absolute minimum code to embed Flash movies in HTML pages. It is not recommended to use the minimum code. There should be a few more attributes added:
• classid is an attribute to the tag. It tells Internet Explorer to load the ActiveX plug-in if it is not installed
• pluginspage is an attribute to the tag. It displays a link to the Shockwave download page if Netscape does not have it
The Flash program can add these attributes for you:
Step 1
Choose File > Publish. Flash will now create the , , and tags for you. It will also create the classid and pluginspage attributes.
Step 2
Open the HTML document that Flash created, view the HTML source and copy the code into your HTML page where you want your Flash movie.
Step 3
Be sure that you have the "somefilename.swf" in your Web folder.
Step 4
Type in the address of the HTML file in your browser and look at your first Flash movie.
Tweening comes from the words "in between".
With Tweening you can go from one keyframe to another and specify changes in the animation and let the Flash program create the frames in between.
________________________________________
Example
In this example you will learn how to make an object move across the screen.
Example
Step 1
Create a small circle to the left in the Stage area. Do this by selecting the circle tool from the left toolbar. Draw the circle in the Stage area.
Step 2
Select the Arrow tool from the left toolbar. Double-click on the circle to select it.
Step 3
Now we have to convert the circle to a symbol. When the circle is converted to a symbol we can create instances of the circle. From the top menu choose Modify > Convert to Symbol. Name the symbol "Ball", and select OK.
Step 4
Go to Frame 10 in the Timeline. Do this by clicking the gray field below 10. Then right click in this field. Choose Insert Keyframe. Keyframes appear as circles in a frame. This operation duplicates the image.
Note: A keyframe specifies changes in an animation. You create keyframes at important points in the Timeline and let Flash create the frames in between.
Step 5
Select the circle and move it to the right a couple of inches.
Step 6
Click on the Timeline any place between Frame 1 and Frame 10. Then right click and choose Create Motion Tween.
Step 7
Choose Control > Test Movie from the top menu to test your Flash movie.
With Motion Guide Tweening you can move an object from one location to another along a specified path.
________________________________________
Example
In this example you will learn how to draw a path an object should follow.
Example
Step 1
Choose Window > Common Libraries > Graphics. Select the image you want to use. In this example we have used a blue mouse.
Step 2
Click on the image and drag it outside the left edge of the Stage.
Step 3
Go to Frame 40 in the Timeline. Do this by clicking the gray field below 40. Then right click in this field. Choose Insert Keyframe. Keyframes appear as circles in a frame. This operation duplicates the image.
Step 4
Click on the Timeline any place between Frame 1 and Frame 40. Then right click and choose Create Motion Tween.
Step 5
Right click on Layer 1 (Click on the layer name, where it says "Layer 1"). Choose Add Motion Guide in the pop-up menu. The Flash program will now insert a motion guide layer on top of layer 1. Motion guide layers are used to draw lines an animated symbol should follow.
Step 6
Click on the Motion Guide Layer to make sure it is the active layer (Click on the layer name, where it says "Guide: Layer 1").
Step 7
Click on the Pencil tool in the left toolbox. Set the Pencil Mode to Smooth (in the Options section of the left toolbox).
Step 8
Draw a line. Begin on the image and draw a line to the other side of the Stage.
Step 9
Go back to Frame 1 in the Timeline. Click on the Arrow tool in the left toolbox. Select the "Snap to Objects" button in the Options section of the left toolbox.
Step 10
Place the image with its center on the beginning of the motion guide (the black line you have drawn with the Pencil). The center of the image shows as a +. A black circle appears when the image is snapped to the motion guide. Release the mouse button when the image is snapped to the guide.
Step 11
Go to Frame 40. Place the image with its center on the end of the motion guide.
Step 12
Choose Control > Test Movie from the top menu to test your Flash movie.
With Tint Tweening you can change the color of an object.
________________________________________
Example
In this example you will learn how to change the color of an object.
Example
Step 1
Choose Insert > New Symbol.
Note: To add Tint effects the object must be a symbol.
Step 2
Name the symbol "changecolor" and select the Graphic option in Behavior. Click OK.
Note: You will now be taken to the symbol generator in the Flash program. Here you create symbols. Symbols can be dragged to the stage of your movie after you have created them.
Step 3
Choose the Text tool in the left toolbox. Choose Text > Size > 36 from the top menu to make the text big. Choose Text > Style > Bold to make the text thick.
Step 4
Click in the work area and write "Color Changing Text".
Step 5
Jump back to the movie. Do this by choosing Edit > Edit Movie.
Step 6
Insert the symbol you just created into the movie. Choose Window > Library. Select the "changecolor" symbol and drag it into the middle of the Stage.
Step 7
Insert a keyframe in Frame 15 and in Frame 30.
Step 8
Go to Frame 15. Right click on the text in the Stage. In the pop-up menu, choose Panels > Effect.
Step 9
Choose Tint from the drop down menu. A color map will show. Set the colors to: R=0, G=255, B=0.
Step 10
Click on the Timeline any place between Frame 1 and Frame 15. Then right click and choose Create Motion Tween.
Step 11
Click on the Timeline any place between Frame 15 and Frame 30. Then right click and choose Create Motion Tween.
Step 12
Choose Control > Test Movie from the top menu to test your Flash movie.
With Shape Tweening you can change one object into another.
________________________________________
Example
In this example you will learn how to change one object into another.
Example
Step 1
Choose the Text tool in the left toolbox. Choose Text > Size > 48 from the top menu to make the text big. Choose Text > Style > Bold to make the text thick.
Step 2
Click in the work area and write "Hello".
Step 3
Right click on the text you just wrote and choose Panels > Align from the pop-up menu.
Step 4
In the Align box select the "To Stage" button first. Then click on the "Align Horizontal Center" button and the "Align Vertical Center" button. Close the Align box.
Step 5
Select the Arrow Tool and click on the text. Choose Modify > Break Apart from the top menu.
Step 6
Insert keyframes at Frame 24, 50 and 51.
Step 7
Delete the text "Hello" in Frame 24. Select it and press the Delete button on your keyboard.
Step 8
Write a new text on the Stage. Write "World!" (Font size: 48, style: bold).
Step 9
Right click on the text you just wrote and choose Panels > Align from the pop-up menu. In the Align box select the "To Stage" button first. Then click on the "Align Horizontal Center" button and the "Align Vertical Center" button. Close the Align box
Step 10
Select the Arrow Tool and click on the text. Choose Modify > Break Apart from the top menu.
Step 11
Insert a keyframe in Frame 26.
Step 12
Double click the keyframe in Frame 1. In the small pop-up box click on the Frame tab. Set Tweening to Shape. Close the pop-up box.
Step 13
Double click the keyframe in Frame 26. In the small pop-up box click on the Frame tab. Set Tweening to Shape. Close the pop-up box.
Step 14
Double click the keyframe in Frame 51. In the large pop-up box click on the Frame Actions tab. Click on the + sign. Choose Basic Actions > Go To. Close the pop-up boxes.
Step 15
Choose Control > Test Movie from the top menu to test your Flash movie.
Example
In this example you will learn how to insert an image, convert it to a button, and add a URL to it so it becomes a link.
Example
Step 1
Choose File > Import to import an image that will become a button. Locate the image and click Open. The image will be saved in the Library.
Step 2
Select the image with the Arrow tool.
Step 3
Convert the image to a symbol. Choose Insert > Convert to Symbol from the top menu. Name the symbol "button", choose Button from the Behavior list and click OK.
Step 4
Right click on the image. Choose Actions from the pop-up menu.
Step 5
In the Object Actions box click on the + sign. Choose Basic Actions > Get URL.
Step 6
Enter a full URL in the URL field (like http://www.w3schools.com).
Step 7
Choose target in the Window field. Close the Object Actions box.
Step 8
Choose Control > Test Movie from the top menu to test your Flash movie.
Example
In this example you will learn how to create your own button and add a URL to it so it becomes a link.
Example
Step 1
Choose Insert > New Symbol from the top menu.
Step 2
Name the symbol "button", choose Button from the Behavior list and click OK. In the Timeline area, you will now see the four states of a button: up, over, down, hit.
Step 3
Select the Rectangle tool, pick a light red Fill Color and draw a rectangle in the work area.
Step 4
Select the Text tool, pick a dark Fill Color and write "Click Me" over the rectangle.
Step 5
Select the Arrow tool and place the text in the middle of the rectangle.
Step 6
Add a keyframe to the Over State in the Timeline. The Over State indicates what should happen when you mouse over the button.
Step 7
Select the Rectangle, change the Fill color to a light green.
Step 8
Choose Edit > Edit Movie to go back to the movie.
Step 9
Choose Window > Library to locate the button. Drag the button into the work area.
Step 10
Right click on the image. Choose Actions from the pop-up menu.
Step 11
In the Object Actions box click on the + sign. Choose Basic Actions > Get URL.
Step 12
Enter a full URL in the URL field (like http://www.w3schools.com).
Step 13
Choose target in the Window field. Close the Object Actions box.
Step 14
Choose Control > Test Movie from the top menu to test your Flash movie.
Example
Example
Step 1
Insert a text in the upper left corner of the Stage area. Do this by selecting the text tool from the left toolbar. Write some text in the "textarea".
Step 2
Select the arrow tool from the left toolbar. Click on the text once to select it.
Step 3
Convert the text to a symbol. From the top menu choose Insert > Convert to Symbol. Name the symbol "text", choose graphic from the Behavior list and select OK.
Step 4
Go to Frame 30 in the Timeline. Do this by clicking the gray field below 30. Then right click in this field. Choose Insert Keyframe. Keyframes appear as circles in a frame.
Step 5
Click on the Timeline any place between Frame 1 and Frame 30. Then right click and choose Create Motion Tween.
Step 6
Go back to Frame 30 in the Timeline. Move the text to the lower right corner.
Step 7
Make sure the text is selected. Choose Modify > Transform > Flip Horizontal.
Step 8
Choose Control > Test Movie from the top menu to test your Flash movie. The text should move from the first location (in frame 1) to the second location (in frame 2). The text should also turn around on its way to the second location.
Example
Example
Step 1
Choose File > Import to import a sound file. Locate the sound file and click Open. The sound file will be saved in the Library.
Step 2
Click in the first frame of "Layer 1" in the Timeline. Choose Window > Panels > Sound from the top menu.
Step 3
In the pop up window (Sound) choose the sound you imported in the Sound field. Choose Stream in the Sync field. Close the pop up window.
Step 4
Go to frame 50 in the Timeline. Right click and choose Insert Frame.
Step 5
Choose Control > Test Movie from the top menu to test your Flash movie.

Learn Basics of Microsoft.NET

2009-02-07T16:16:00.000+05:30

Microsoft .NET is Microsoft's new Internet strategy.
.NET was originally called NGWS.
________________________________________
NGWS - Next Generation Windows Services
Before the official announcement of .NET, the term NGWS was used for Microsoft's plans for producing an "Internet-based platform of Next Generation Windows Services".
Steve Ballmer quote January 2000:
"Delivering an Internet-based platform of Next Generation Windows Services is the top priority of our company. The breakthroughs we’re talking about here include changes to the programming model, to the user interface, to the application integration model, the file system, new XML schema....."
________________________________________
Microsoft. NET
The Microsoft. NET strategy was presented by Microsoft officials to the rest of the world in June 2000:
• .NET is Microsoft's new Internet and Web strategy
• .NET is NOT a new operating system
• .NET is a new Internet and Web based infrastructure
• .NET delivers software as Web Services
• .NET is a framework for universal services
• .NET is a server centric computing model
• .NET will run in any browser on any platform
• .NET is based on the newest Web standards
________________________________________
.NET Internet Standards
.NET is built on the following Internet standards:
• HTTP, the communication protocol between Internet Applications
• XML, the format for exchanging data between Internet Applications
• SOAP, the standard format for requesting Web Services
• UDDI, the standard to search and discover Web Services
________________________________________
.NET Framework
The .NET Framework is the infrastructure for the new Microsoft .NET Platform.
The .NET Framework is a common environment for building, deploying, and running Web Services and Web Applications.
The .NET Framework contains common class libraries - like ADO.NET, ASP.NET and Windows Forms - to provide advanced standard services that can be integrated into a variety of computer systems.
The .NET Framework is language neutral. Currently it supports C++, C#, Visual Basic, JScript (The Microsoft version of JavaScript) and COBOL. Third-party languages - like Eiffel, Perl, Python, Smalltalk, and others - will also be available for building future .NET Framework applications.
The new Visual Studio.NET is a common development environment for the new .NET Framework. It provides a feature-rich application execution environment, simplified development and easy integration between a number of different development languages.
________________________________________
Additional Information
• The .NET plan includes a new version of the Windows operating system, a new version of Office, and a variety of new development software for programmers to build Web-based applications.
• The background for .NET is part of Microsoft's new strategy to keep Windows the dominant operating system in the market, as computing begins to move away from desktop computers toward Internet enabled devices, such as hand-held computers and cell phones.
• The most visual components of the new .NET framework are the new Internet Information Server 6.0, with ASP.NET and ADO.NET support, Visual Studio.NET software tools to build Web-based software, and new XML support in the SQL Server 2000 database.
• Bill Gates is supervising the .NET project.
.NET Building Blocks

________________________________________
.NET Building Blocks is a set of core Internet Services.
________________________________________
Web Services
Web Services provide data and services to other applications.
Future applications will access Web Services via standard Web Formats (HTTP, HTML, XML, and SOAP), with no need to know how the Web Service itself is implemented.
Web Services are main building blocks in the Microsoft .NET programming model.
________________________________________
Standard Communication
Official Web standards (XML, UDDI, SOAP) will be used to describe what Internet data is, and to describe what Web Services can do.
Future Web applications will be built on flexible services that can interact and exchange data, without the loss of integrity.
________________________________________
Internet Storages
.NET offers secure and addressable places to store data and applications on the Web. Allowing all types of Internet devices (PCs, Palmtops, Phones) to access data and applications.
These Web Services are built on Microsoft's existing NTFS, SQL Server, and Exchange technologies.
________________________________________
Internet Dynamic Delivery
Reliable automatic upgrades by demand and installation independent applications.
.NET will support rapid development of applications that can be dynamically reconfigured.
________________________________________
Internet Identity
.NET supports many different levels of authentication services like passwords, wallets, and smart cards.
These services are built on existing Microsoft Passport and Windows Authentication technologies.
________________________________________
Internet Messaging
.NET supports integration of messaging, e-mail, voice-mail, and fax into one unified Internet Service, targeted for all kinds of PCs or smart Internet devices.
These services are built on existing Hotmail, Exchange and Instant Messenger technologies.
________________________________________
Internet Calendar
.NET supports Internet integration of work, social, and private home calendars. Allowing all types of Internet devices (PCs, Palmtops, Phones) to access the data.
These services are built on existing Outlook and Hotmail technologies.
________________________________________
Internet Directory Services
.NET supports a new kind of directory services that can answer XML based questions about Internet Services, far more exactly than search engines and yellow pages.
These services are built on the UDDI standard.
________________________________________
NET Software

________________________________________
.NET is a mix of technologies, standards and development tools
________________________________________
Windows.NET
Today, Windows 2000 and Windows XP form the backbone of .NET.
In the future, the .NET infrastructure will be integrated into all Microsoft's operating systems, desktop and server products.
Windows.NET is the next generation Windows. It will provide support for all the .NET building blocks and .NET digital media. Windows.NET will be self-supporting with updates via Internet as users need them.
________________________________________
Office.NET
A new version of Microsoft Office - Office.NET - will have a new .NET architecture based on Internet clients and Web Services.
With Office.NET, browsing, communication, document handling and authoring will be integrated within a XML-based environment which allow users to store their documents on the Internet.
________________________________________
ASP.NET
ASP.NET is the latest version of ASP. It includes Web Services to link applications, services and devices using HTTP, HTML, XML and SOAP.
New in ASP.NET:
• New Language Support
• Programmable Controls
• Event Driven Programming
• XML Based Components
• User Authentication
• User Accounts and Roles
• High Scalability
• Compiled Code
• Easy Configuration
• Easy Deployment
• Not ASP Compatible
• Includes ADO.NET
You can read more about ASP.NET and ADO.NET in our ASP.NET Tutorial.
________________________________________
Visual Studio.NET
The latest version of Visual Studio - Visual Studio.NET - incorporates ASP.NET, ADO.NET, Web Services, Web Forms, and language innovations for Visual Basic. The development tools have deep XML support, an XML-based programming model and new object-oriented programming capabilities.
________________________________________
Visual Basic.NET
Visual Basic.NET has added language enhancements, making it a full object-oriented programming language.
________________________________________
SQL Server 2000
SQL Server 2000 is a fully web-enabled database.
SQL Server 2000 has strong support for XML and HTTP which are two of the main infrastructure technologies for .NET.
Some of the most important new SQL Server features are direct access to the database from a browser, query of relational data with results returned as XML, as well as storage of XML in relational formats.
________________________________________
Internet Information Services 6.0
IIS 6.0 has strong support for more programming to take place on the server, to allow the new Web Applications to run in any browser on any platform.
.NET Web Services

________________________________________
Web services are small units of code built to handle a limited task.
________________________________________
What are Web Services?
• Web services are small units of code
• Web services are designed to handle a limited set of tasks
• Web services use XML based communicating protocols
• Web services are independent of operating systems
• Web services are independent of programming languages
• Web services connect people, systems and devices
________________________________________
Small Units of Code
Web services are small units of code designed to handle a limited set of tasks.
An example of a web service can be a small program designed to supply other applications with the latest stock exchange prices. Another example can be a small program designed to handle credit card payment.
________________________________________
XML Based Web Protocols
Web services use the standard web protocols HTTP, XML, SOAP, WSDL, and UDDI.
HTTP
HTTP (Hypertext Transfer Protocol) is the World Wide Web standard for communication over the Internet. HTTP is standardized by the World Wide Web Consortium (W3C).
XML
XML (eXtensible Markup Language) is a well known standard for storing, carrying, and exchanging data. XML is standardized by the W3C.
You can read more about XML in our XML tutorial.
SOAP
SOAP (Simple Object Access Protocol) is a lightweight platform and language neutral communication protocol that allows programs to communicate via standard Internet HTTP. SOAP is standardized by the W3C.
You can read more about SOAP in our SOAP tutorial.
WSDL
WSDL (Web Services Description Language) is an XML-based language used to define web services and to describe how to access them. WSDL is a suggestion by Ariba, IBM and Microsoft for describing services for the W3C XML Activity on XML Protocols.
You can read more about WSDL in our WSDL tutorial.
UDDI
UDDI (Universal Description, Discovery and Integration) is a directory service where businesses can register and search for web services.
UDDI is a public registry, where one can publish and inquire about web services.
________________________________________
Independent of Operating Systems
Since web services use XML based protocols to communicate with other systems, web services are independent of both operating systems and programming languages.
An application calling a web service will always send its requests using XML, and get its answer returned as XML. The calling application will never be concerned about the operating system or the programming language running on the other computer.
________________________________________
Benefits of Web Services
• Easier to communicate between applications
• Easier to reuse existing services
• Easier to distribute information to more consumers
• Rapid development
Web services make it easier to communicate between different applications. They also make it possible for developers to reuse existing web services instead of writing new ones.
Web services can create new possibilities for many businesses because it provides an easy way to distribute information to a large number of consumers. One example could be flight schedules and ticket reservation systems.

Executables, C++ (and Java too) must die
Neither C++ nor Java can ever create standard components that can run on all computers. There is no room for these languages in future distributed applications. Executables are not standard. COM objects are not standard, DLL-files are not standard. Registry settings are not standard. INI-files are not standard. None of these components must be allowed to destroy your dream of a standard distributed application that will run on almost any computer in the world.
________________________________________
Clients must be Standard Internet Browsers
Application clients must be standard clients without any additional components. No part of the applications must be stored on client computers. The application must never use, or rely on, any components, dll- or ini-files, registry settings or any other non standard settings or files stored on the client computer. (Then you can start calling it a Thin Client). Our best suggestion is to let all clients use standard Internet browsers like Internet Explorer, Netscape, or Firefox running on Windows or Mac computers.
________________________________________
Servers must be Standard Internet Servers
Application servers must be standard Internet servers running standard software without any additional components. The application must never use, or rely on, any components, dll- or ini-files, registry settings or any other non standard settings or files stored on the server. Our best suggestion is to use a standard Internet server like Internet Information Services (IIS), with a standard request-handler like Active Server Pages (ASP), and a standard database connector like Active Data Objects (ADO). As your data-store you should use a standard SQL based database like Oracle or Microsoft's SQL Server.
________________________________________
Applications must use Internet Communication
Application clients and servers must not be allowed to communicate via any proprietary protocol. Clients must request servers via a standard Internet protocol and servers must respond via the same protocol. Clients must be able to use any service without having to maintain a permanent connection to the server. Our best suggestion is to let servers be requested with standard stateless Internet HTTP requests. Servers should respond with a standard stateless Internet HTTP response.
The paragraphs below describes W3Schools' vision about future Internet Distributed Applications.
________________________________________
Applications must be a Set of Services
Applications can no longer be allowed to contain large masses of compiled executable code. Applications must be broken down into a number of smaller individual services that are easier to create and easier to maintain. Individual services should be developed and maintained by smaller groups of people. Services are not the same as executables, or components, or DLL's. Services should be answers to submitted requests. Services should be returned as data. Our best suggestion is to develop services as a number of server-side HTML and/or XML pages.
________________________________________
Services must not be Purpose Built
Our history is full of applications that were purpose built for a single task. Many of these applications died before they were introduced, because they could not manage new changes in the requirements. This is a terrible waste of money and time. We (and the people that pay for our applications) want to create flexible applications that are so generalized that they can gracefully support future changes. Future - not even thought about - changes should easily hook into our application without crumbling or destroying it. Our best suggestion is to create flexible standard services that can be used to serve a lot of different requests.
________________________________________
Services must be easy to Create and Edit
Services should not be coded if it can be avoided. If a service has to be coded, our best suggestion is to use scripts. Services should never be compiled into executables. That makes services too hard to access and to edit. Any pre-compiled component used in an application will threaten the possibility of creating an application that can move, scale and gracefully support future extensions or changes. Services should be created and modified by editing their properties and methods, not by changing their executable code. Our best suggestion is to use an XML editor to create and edit services, and to use a standard service engine to provide services by executing the service description. The service descriptions should be stored in a data store like a database or in an XML/HTML file.
________________________________________
Services and data must be Self Describing
Application clients must be able to query a server for a service and to ask for the current server functions. Clients and servers must also be able to exchange data in a way so that both understand each element in the data. Our best suggestion is to use an XML based information vocabulary with a DTD (Document Type Definition) to exchange server functions, and to use XML to exchange data.

Imporatnt Tactics For Programming

2009-02-07T16:15:00.000+05:30

How to use printf function without semicolon?

There are several ways to do this, below are some of the most popular ones:
• if(printf("Hello, World!\n")) { }

• while(!printf("Hello, World!\n")) { }

• switch(printf("Hello, World!\n")) { }

How to swap two numbers without using temporary variable ?
This one would figure in anyone's list of elite questions in Orkut programming communities that are guaranteed a minimum of 50 responses everytime someone raises it, if at all anyone were to be jobless enough to compile one such list. This question is often asked in many interviews in India and so obviously many would be interested in knowing the answer.

And it would come as a rude jolt to many when confronted and told that there is no standard conformant way of doing this which would apply equally well to all built-in types.

I would like to discuss all the solutions that have been offered so far.

a=a+b;
b=a-b;
a=a-b;

The above method wont work because it doesn't take into account overflow errors. Suppose for example if we had to swap two signed numbers 1 and 32767 on a system where int is 16 bits long. On such a system, the maximum value an int can store (INT_MAX) would typically be 32767.

So when the first step a+b is executed the result would be 32768, which would be larger than the maximum value that can be stored in an int variable. Consequently this value cant be stored in a and hence an overflow occurs. What happens after this is undefined. No matter what happens under the hood, the result is bound to be undefined and hence this method fails whenever an overflow occurs.

a=a*b;
b=a/b;
a=a/b;

This method would fail for the same reason the previous code snippet would fail. Here a*b can overflow. This has more problems as well. a/b can overflow too. This method would also fail if b were zero, as it would cause divide by zero error. So this is another worthless suggestion.

a=a^b;
b=b^a;
a=a^b;

The method above wont work for floating point values. Bitwise operators are not defined for floating points and hence this solution can be used only when the numbers to be swapped are not floating points. Usage of this method on variables other than int (char, long, short) would result in Undefined Behavior(UB). In all the three methods above, the compiler implicitly uses temporary values to store the result from the mathematical operations and this temporary value is then copied into the l-value. So technically we are using temporary values here too. But let us proceed assuming that the question here is to swap two variables without defining any temporary variable in the user code.

a^=b^=a^=b;

a=a+b-b=a;

The two code snippets shown above impresses almost every newbie the first time they see it. They would leave no stone unturned in praising the author of this code. Little do they realize that this code is not guaranteed to produce the same result on every system they test it on.

Here we are entering the realm of Undefined Behavior often abbreviated as UB.

There are three kinds of operators: unary, binary and ternary. Unary operators are those which operate on one and only one operand. Unary+, Unary-,dereferencing operator* are some examples. Binary operators are those which operate on two operands. Addition (+), Subtraction (-), Logical Or (||) are a few examples of binary operators. There is only one ternary operator in C++ viz ?:.

When the compiler sees an expression, it breaks them into smaller units depending on a table called the operator precedence table∞. The operators at the top of the table are the ones executed first followed by other operators in the decreasing order of precedence.

Now each of these operators can operate on one, two or three operands. These operands can themselves be expressions.

For example : int a=(b+c)*(d+e);

Here the operator * has two operands. The former is a simple expression (b+c) and the latter is another simple expression (d+e).

Now the C++ standard doesn't place any condition on the order in which these expressions must be evaluated. A normal human being would first calculate (b+c) and store it in a temporary variable. He would then calculate (d+e) and store it in another temporary variable. He would then retrieve these two temporary values and then multiply them and store the result in the variable a. But the standard lays down no such conditions or rules. It leaves the choice to the compilers. So the compilers can evaluate either (d+e) first or (b+c) first. Different compilers choose to do it differently.

For the simple expression given above this doesn't cause much confusion. The reader would probably be wondering as to why I am rambling on about it when evaluating (b+c) or (d+e) first doesn't change the result.

Surprise!!!

Consider this expression:

int i=1;
int temp=i++*(i-1);

Here the operands of the multiplicative operator * are i++ and i-1;

Now as mentioned before the compiler can evaluate either i++ first or (i-1) first. Let us see what happens when i++ is evaluated first. After i++ is evaluated the value that would be returned would be the existing value i.e. 1 and i would now be 2. After this i-1 is evaluated which would be 1. So i++*(i-1) would be 1*1 which is equal to 1. So temp would be 1 now.

Now let us see what happens when (i-1) is evaluated first. Since i is 1, i-1 becomes zero. Irrespective of what i++ is now, i++*(i-1) would be zero. So temp is initialized to zero here.

Do you realize the mistake? The result here depends on the order of evaluation and hence is unpredictable. It is unreasonable to expect all compilers to follow the same order of evaluation. Hence temp will be initialized to 1 on some systems and it will be initialized to zero on some other systems. This is Undefined Behavior and it is more often than not better to avoid coding practices like these.

Now this brings me to the discussion of sequence points. I have tried hard and exhausted myself in the process of trying to convince people that they should pay special attention to this topic. Please check C-faq∞ and Wikipedia article∞ for more info on sequence points.

After reading those topics some users confuse themselves between operator precedence and sequence points. Sequence points has got nothing to do with operator precedence. This requires more explanation.

When a compiler sees an expression with many operators, it breaks the expression into many logical and simpler units. How it does this depends on operator precedence.

For example when the compiler sees an expression like a+b*c+d, here the two operands are binary multiplicative operator * and binary addition operator +. * has higher precedence.

So the first step would be to choose * as the point where the expression can be split into simpler units. So the expression would now become a+(b*c)+d.

This expression is evaluated from left to right as + has left to right associativity. So the expression would become ( a + (b*c) ) + d

Now assuming a and d are simple expressions themselves. In this case consider the first binary addition operator.

Its operands are d and ( a + (b*c) ). Now as I mentioned before, the compiler can evaluate either d first or it can evaluate ( a + (b*c) ) first.

Now if it chooses to evaluate ( a+ (b*c) ) first, it can further choose to evaluate (b*c) first or a first. And further if b and c were expressions themselves, then we cant be sure about which amongst b or c would be evaluated first. The standard doesn't guarantee much here.

So the expression a+b*c+d which appears so simple to the naked eye has so many complications when we enter the realm of compilers and it is always better not to assume anything.

Hope that clears things a bit.

Now coming back to the original discussion. Why do those two code snippets lead to UB?

For precisely the same reason (i++)*(i-1) leads to UB. In the first code snippet there are many XOR operations operating on the two variables a and b. The author of the code ends up modifying the variables a and b more than once between two sequence points which results in UB.

In the second code snippet, the author assumes that b=a would be evaluated first before all other expressions. It may or may not be evaluated first. The results would be different for both the cases and hence leads to be UB again.

Now to summarize, there is no known way to swap two variables without using a third variable that would apply equally well to all built-in types.
Below is one more way to add two numbers without the arithmetic operators. This method makes use of the asterisk(*) field width specifier in the printf function and use the returned value from printf. Here the printf statement is given with field width operator in format, and the two numbers are given as argument for field widths, hence we are printing a total width of two given integer arguments. The printf function returns the number of characters printed, and here the total number of characters printed will be sum of a and b. The third and fifth arguments are zero length strings because it only needs to print the total width of two integers.
Note that this method only works for unsigned integers.

unsigned add(unsigned a, unsigned b)
{
return printf("%*s%*s", a, "", b,"");
}

How to find whether a given number is even or odd without using % (modulus) operator ?
A newbie question. Here is a simple C++ solution.

bool isOdd(int num){
return num&1?true:false;
}

If the number is odd then it's least significant bit (LSB) is set i.e. it is 1. If it is even then it is 0. When you bitwise and (&) this number with 1, the result would be either 1 if the number is odd or zero if it is even.

As rightly pointed out by SpS, the same code can be implemented in C (following C99 standard) as

#include
bool isOdd(int num){
return (num&1)?true:false;
}

Here stdbool.h defines the macros bool, true and false. The macro bool is defined to be _Bool (the boolean type according to C99 standard). true is a macro which expands to the decimal constant 1 and false is a macro which expands to decimal constant 0.

For C89 sticklers

int isOdd(int num){
return (num&1);

How to find whether the given number is a power of 2 in single a single step (without using loops) ?

Ok this is another often repeated question. But unlike the others, this has a legitimate solution.

Before I show you the code for this, I would like to explain a few things first. We are required to find if a number is a power of 2 in just one step. A number would be a power of two if there is exactly one bit that is equal to 1 in its bit pattern (even 1 is a power of 2. 2 raised to the power zero is 1). Now we could use the method that we used to count the number of bits that are 1 in a given number and check if it is equal to 1. However that approach needs many steps and hence wont suffice here.

In a number which is an exact power of 2 only 1 bit is set and all others are zero. Let the position of this 1 bit be MSB. Mathematics rules for binary numbers tells us that if we subtract 1 from this number then the number that we would get would have all its bit starting from the bit position MSB+1 set to 1. For example if the given number num is 8(00001000) then num-1 would be 7 (00000111). Now we notice that these two bit patterns dont have a 1 in the same bit position. Further observation suggests that if we bitwise and (&) both these numbers we would get zero.

It can also be proved that num&(num-1) would be zero only if num is a power of 2. I leave that as an exercise. If you are'nt able to figure out why it is so, then just leave a comment here and I will explain that part too.

Now here is the code:

bool isPowerOf2(int num){
return ((num>0) && (num & (num-1))==0);
}
How to find greatest of two/three/four numbers without using relational operators ?

Finding greatest of two numbers:
• int maxof2(int a,int b)
{
return (a + b + abs(a - b))/2;
}

• /****************************************************
Purpuse : Evaluate the bigger one of two integers.
Author : ALNG
Date : 2003-03-11
Original : http://search.csdn.net/Expert/topic/1515/1515035.xml
**************************************************/

inline int signof(int i)
{
return unsigned(i) >> (sizeof (int) * 8 - 1);
}

int max(int a, int b)
{
int p[2];
p[0] = a;
p[1] = b;

return p[signof(a - b)];
}

Function for finding greatest of three numbers:
int maxof3(int a, int b, int c)
{
return (a + b + c * 2 + abs(a - b) + abs(a + b - c * 2 + abs(a - b))) / 4;
}

Function for finding greatest of four numbers:
int maxof4(int a, int b, int c, int d)
{
return (a + b + c + d + abs (b - a) + abs(d - c) + abs(a + b - c - d + abs( b - a) - abs(d - c)))/ 4;
}

How to print 1 to n(a user defined value) without using any kind of loops or recursion ?
This is is very easy to implement in C++ using a constructor and a static member to count the number of objects instantiated of that class as shown in the below code:

C++

#include

class a{
public:
a(){std::cout<<++i< private:
static int i;
};

int a::i; //allocates memory for the static variable

int main(){
int n=0;
std::cout<<"Enter the maximum number that you want to print: ";
std::cin>>n;
a* array=new a[n]; //this statement prints 1 to n because creating an array of n objects calls the default class constructor n times
return 0;
}

Note: This does use implicit loop when objects are created, but there aren't any explicit looping statements or recursion in the program.

For C language, we can do this using setjmp and longjmp as given in the below code. Again there is an implicit loop, but no explicit looping construct or recursion used.

#include
#include

static jmp_buf jmpbuf;
static int val = 1, n;

void printvalue(void)
{
printf("%d\n",val++);
longjmp(jmpbuf,val);
}

int main()
{
printf("Enter the N value:");
scanf("%d",&n);
if (setjmp(jmpbuf) > n)
return 0;
else
printvalue();
}

What is wrong with using void main()? Where does the returned value from main() go?

The main() function has to return an integer value which indicates the exit status of the program. The C and C++ standards only allow declarations for main function in the below forms:
• int main(void) { /* ... */ }

• int main(int argc, char *argv[ ]) { /* ... */ }

Or any other form which is equivalent of the above two, such as int main() and int main(int argc, char **argv).
Program to print its own source code as output
A Program which reproduces its own source code is called as a quine.
There are lots of ways to do this, here are some of them:
• main(){char *c="main(){char *c=%c%s%c;printf(c,34,c,34);}";printf(c,34,c,34);}

• main(){char*a="main(){char*a=%c%s%c;int b='%c';printf(a,b,a,b,b);}";int b='"';printf(a,b,a,b,b);}

What are the differences between C and C++ ?

Can you write a code which compiles in C but not in C++ ?
This question puzzles many who believe that C++ is a superset of C language, and all C language code is valid in C++. But it is not true and you should read the differences between C and C++ to know how they are different.

Below are few examples which compiles in C and would fail to compile in C++:
Example 1:

#include
int main()
{
int class;
class=10;
printf("%d",class);
}

This will not compile under C++ because class is a keyword, but will compile in C without any problems. Similarly any keywords which are specific to C++ such as public, private, virtual, friend etc can be used as identifiers in C, but not in C++.

Example 2:

int fun()
{
//some code
}
int main()
{
fun(10,20);
}

This will fail to compile in C++, because in C++, the declaration of a function with no argument list is equivalent to declaring it as function with void parameter list. But in C language, it means a function with unspecified number of arguments and we can pass any number of arguments to this function in C.

Example 3:

#include
int main()
{
int *array=malloc(sizeof(int)*100);
}

This is valid in C because a pointer of type void* can be assigned to any other pointer without cast, but this is not in valid C++ because will have to give an explicit cast to it as in:
int *array=(int*)malloc(sizeof(int)*100);

Example 4:

#include
int main()
{
static int i=5;
if(i>0)
printf("%d\n",i);
else
{
i--;
main();
return 0;
}
}

What are far, huge and near qualified pointers?
What are far, huge and near qualified pointers?
How to count the number of 1's (set bits) in a given number ?

This is another question that confounds most of the newbies in Orkut and they end up confusing themselves and the others.

There are many ways you can do this, below are a few naive methods for the beginners:

int countBits(unsigned num){
int count= 0;
while(num){
count += num & 1;
num >>= 1;
}
return count;
}

int countBits(unsigned num){
for(unsigned int count=0; num; count++){
num&=num-1;
}
return count;
}

Here is how you can do it in C++ using the bitset class provided in the STL.

int countBits(int num){
std::bitset temp(num);
return temp.count();
}
What are wild and dangling pointers?
A pointer which is not initialized with any address is called as a wild pointer. It may contain any garbage address, so dereferencing a wild pointer is dangerous(as it causes undefined behavior). A dangling pointer is a pointer which no longer points to any valid location. It is just as dangerous as wild pointer as it contains invalid location.

Example:

#include
int main()
{
int *p; /*At this point, the pointer p is a wild pointer. Its uninitialized, so it may have any random address in it*/
p=malloc(sizeof(int)*10); /* p is initialized with the address to an array of 10 integers */
free(p); /* p becomes dangling pointer as it no longer points to a valid location. */
p=NULL; /* p is no longer dangling pointer as it now initialized with NULL*/
}

How can we return more than one value from a function?

One simple way is to embed the different values that we want to return in a struct and then return the struct.
Example:

struct data
{
int a;
float b;
}

struct data myFunction(void)
{
struct data x;
/*set values for the members of x*/
return x;
}

int main()
{
struct data myData;
myData=myFunction();
/*Now you can access the different values within myData structure*/
return 0;
}

The other way around is to pass the pointers to different objects as argument to the function.
Suppose, you need a function fun1() to return one integer value and three float values, then, declare fun1() as:
int fun1(float *x, float *y, float *z);

Example:

int fun1(float *x, float *y, float *z)
{
int status;
/*Set the values of *x, *y, *z and status*/
return status;
}

While calling the function, pass address of three float variables in which you want to store the returned values, like:
x = fun1(&float1, &float2, &float3);

DB Interview Questions

2009-02-07T16:12:00.000+05:30

DB Interview Questions
Question: What is SQL?

Question: What is SELECT statement?

Question: How can you compare a part of the name rather than the entire name?

Question:
What is the INSERT statement?

Question: How do you delete a record from a database?

Question: How could I get distinct entries from a table?

Question: How to get the results of a Query sorted in any order?

Question: How can I find the total number of records in a table?

Question: What is GROUP BY?

Question: What is the difference among "dropping a table", "truncating a table" and "deleting all records" from a table?

Question: What are the Large object types suported by Oracle?

Question: Difference between a "where" clause and a "having" clause ?

Question: What's the difference between a primary key and a unique key?

Question: What are cursors? Explain different types of cursors. What are the disadvantages of cursors? How can you avoid cursors?

Question: What are triggers? How to invoke a trigger on demand?

Question: What is a join and explain different types of joins.

Question: What is a self join?

Q: What is SQL?
A: SQL stands for 'Structured Query Language'.

Q: What is SELECT statement?
A: The SELECT statement lets you select a set of values from a table in a database. The values selected from the database table would depend on the various conditions that are specified in the SQL query.

Q: How can you compare a part of the name rather than the entire name?
A: SELECT * FROM people WHERE empname LIKE '%ab%'
Would return a recordset with records consisting empname the sequence 'ab' in empname .

Q: What is the INSERT statement?
A: The INSERT statement lets you insert information into a database.

Q: How do you delete a record from a database?
A: Use the DELETE statement to remove records or any particular column values from a database.

Q: How could I get distinct entries from a table?
A: The SELECT statement in conjunction with DISTINCT lets you select a set of distinct values from a table in a database. The values selected from the database table would of course depend on the various conditions that are specified in the SQL query. Example
SELECT DISTINCT empname FROM emptable

Q: How to get the results of a Query sorted in any order?
A: You can sort the results and return the sorted results to your program by using ORDER BY keyword thus saving you the pain of carrying out the sorting yourself. The ORDER BY keyword is used for sorting.

SELECT empname, age, city FROM emptable ORDER BY empname

Q: How can I find the total number of records in a table?
A: You could use the COUNT keyword , example

SELECT COUNT(*) FROM emp WHERE age>40

Q: What is GROUP BY?
A: The GROUP BY keywords have been added to SQL because aggregate functions (like SUM) return the aggregate of all column values every time they are called. Without the GROUP BY functionality, finding the sum for each individual group of column values was not possible.

Q: What is the difference among "dropping a table", "truncating a table" and "deleting all records" from a table.
A: Dropping : (Table structure + Data are deleted), Invalidates the dependent objects ,Drops the indexes
Truncating: (Data alone deleted), Performs an automatic commit, Faster than delete
Delete : (Data alone deleted), Doesn’t perform automatic commit

Q: What are the Large object types suported by Oracle?
A: Blob and Clob.

Q: Difference between a "where" clause and a "having" clause.
A: Having clause is used only with group functions whereas Where is not used with.

Q: What's the difference between a primary key and a unique key?
A: Both primary key and unique enforce uniqueness of the column on which they are defined. But by default primary key creates a clustered index on the column, where are unique creates a nonclustered index by default. Another major difference is that, primary key doesn't allow NULLs, but unique key allows one NULL only.

Q: What are cursors? Explain different types of cursors. What are the disadvantages of cursors? How can you avoid cursors?
A: Cursors allow row-by-row prcessing of the resultsets.
Types of cursors: Static, Dynamic, Forward-only, Keyset-driven. See books online for more information.
Disadvantages of cursors: Each time you fetch a row from the cursor, it results in a network roundtrip, where as a normal SELECT query makes only one rowundtrip, however large the resultset is. Cursors are also costly because they require more resources and temporary storage (results in more IO operations). Furthere, there are restrictions on the SELECT statements that can be used with some types of cursors.
Most of the times, set based operations can be used instead of cursors.

Q: What are triggers? How to invoke a trigger on demand?
A: Triggers are special kind of stored procedures that get executed automatically when an INSERT, UPDATE or DELETE operation takes place on a table.
Triggers can't be invoked on demand. They get triggered only when an associated action (INSERT, UPDATE, DELETE) happens on the table on which they are defined.
Triggers are generally used to implement business rules, auditing. Triggers can also be used to extend the referential integrity checks, but wherever possible, use constraints for this purpose, instead of triggers, as constraints are much faster.

Q: What is a join and explain different types of joins.
A: Joins are used in queries to explain how different tables are related. Joins also let you select data from a table depending upon data from another table.
Types of joins: INNER JOINs, OUTER JOINs, CROSS JOINs. OUTER JOINs are further classified as LEFT OUTER JOINS, RIGHT OUTER JOINS and FULL OUTER JOINS.
Q: What is a self join?
A: Self join is just like any other join, except that two instances of the same table will be joined in the query.