wt is the major difference b/t if-else-if and switch statments  

The if statement is used to select among two alternatives. It uses a boolean expression todecide which alternative should be executed. The switch statement is used to select among multiple alternatives. It uses an int expression to determine which alternative should be executed.

Typically, nested if-else statements are used in the program's logic where there isn't only one condition to evaluate. A switch statement, on the other hand, evaluates only one variable and starts to work there. You can think of a switch statement as a simplified (and stripped-down) version of an if-else block.

switch(x) {
case 1: // do this
case 2: // do this
case 3: // do this
// etc
}

The nested if-else statement's power comes from the fact that it is able to evaluate more than one condition at once, and/or use lots of different conditions in one logical structure.

if(x == 0) {
// do this
} else if(y == 1) {
// do this
} else if(x == 1 && y == 0) {
// do this
}

If you're going to evaluate only one variable in the condition statement, you're better off going with a switch statement, since it looks a lot neater than nested ifs. However, like in the case above, there are times where the only structure you could use is an if-else block, so you don't have much of a choice.

Answered by Nagendra at 8:57 AM on May 06, 2008

Well,
The major difference B/T if-else-if statement and Switch statement is that if-else-if statement is used to satisfy some condition.

if( condition )/*true*/
{
}
else
{
if( another_condition )/*conditon true*/
{
}
else/*if both the conditon not get satisfied then this statement get executed*/
{
}

BUT on the other hand Switch statement is used in selection or used in menu driven programms.

switch( i )/*where i is an integer that chooses by user what he waana to do */
{
case 1 :
do_something();
// Now fall into case 2 and do that, too.
case 2 :
do_something_else();
break ;
default :
break;

Answered by ajay kumar at 1:06 AM on April 18, 2008

The switch statement is very similar to the if-else-if ladder of selection statements. Here is its general form:

switch(expression)
{
case constant_1:
statement_1 or block_1;
break;
case constant_2:
statement_2 or block_2;
break;
case constant_1:
statement_3 or block_3;
break;

// More cases may follow

default
statement_X or block_X
}

In the switch construct, as in the if-else-if construct, multiple possible blocks of code are being selected from, and only one of them will typically be executed. Each case or possible block of code is initiated by the appearance of the case reserved word, and is terminated by the appearance of the break reserved word. (The break is not required, but is almost always used.) The if-else-if and the switch structures have very similar usage in a program, but there are distinct differences. These differences are presented in the table below.

if-else construct
switch construct
An expression is evaluated and the code is selected based on the truth value of the expression. An expression is evaluated and the code is selected based on the value of the expression.
Each if has its own logical expression to be evaluated as true or false. Each case is referring back to the original value of the expression in the switch statement.
The variables in the expression may evaluate to a value of any type, either an int or a char. The expression must evaluate to an int.

There is one subtle but very important difference between the if-else-if ladder and the switch statement. That difference involves the break statement. In the if-else-if ladder, no matter what, only one of the blocks of code is executed. In the switch construct, if the break statement is omitted, the flow of execution will go forward into the next block. Leaving out a break is sometimes useful, but pretty rare. If you are missing a break statement in any block, make sure you intended to leave it out!

Example

#include

int main(void)
{
float a, b;
char operation;

cout << "Enter a number, an operation, and a number:";
cin >> a >> operation >> b;
cout << endl << endl << "The answer, Master, is: ";

switch (operation)
{
case '+':
cout << a + b;
break; // Without this statement, execution
// continues on to case '-'
case '-':
cout << a - b;
break;

case 'x': // Users may use either symbol for
// multiplication.
case '*': // Notice that for either case, the next
// block will be executed.
cout << a * b;
break; // Without this statement, execution
// continues on to case '/'
case '/':
cout << a / b;
break;
}
return(0);
}

Another example, one which uses more selection structures than just switch, is the problem of finding the possible number of roots of a polynomial function will depend on the degree, or value of the highest exponent in the polynomial. In a program to report how many roots a polynomial has, we might see the following code. Recall that a polynomial of degree 1 is a linear function. The twist in this case is that more than one case value will result in the same output. In a situation like this, the different case constants can be listed immediately before the code that should be executed, without each case having a break statement.

// code fragment to describe the number of solutions
// of a polynomial function (degree < 10).
// Assume that the coefficients are a0, a1, a2, a3, and so on,
// and that the degree of the polynomial has already been calculated.

switch(degree) // Which code to execute depends on
// the degree of the poly

Answered by Shilpa Behl at 10:00 PM on April 17, 2008

You should use switch statements if you have multiple choices. It also makes your code easier to read.
There are lots of things that a switch statement can't be used for bit as a general rule if a switch statement can be used and you have 3 or more cases then a switch statement is a better choice. In today's modern world, the performance difference is actually negligible. You will usually have more performance problems due to creating unnecessary objects or increasing referential integrity, or etc.

Answered by Kajal at 8:52 PM on April 17, 2008

If-else-if is a branching statement in computer languages. It is used to branch on one of the code based on the condition.
Switch is a selective statement. It selects one code from many of the codes available.

Answered by Kamlesh B at 4:24 PM on April 17, 2008

Braces: open/close aligned vertically and placed at the level of the surrounding code. All of the following examples demonstrate this. Also, except for the single (I believe) exception of the while in a do / while , I never have any code on the same line as a brace. However, braces are a great place to add a comment describing the purpose of the block or to put a reference to what block is ending (when the blocks are large and/or many end close together).
switch / case : braces and case align with the �s' in switch . The logic for this is that the braces mark a block of code that exists at the same level as the switch . You will notice that the case lines are indented to the same depth as the switch itself. The logic for that choice is that the switch and case as a group comprise a single control structure that exists at the indentation level where it began (with the switch ). A pleasant result of this is that we don't end up indenting the actual code within a switch twice and heading off into indent oblivion. For example:

switch( cond1 )
{
case 1 :
do_something();
// Now fall into case 2 and do that, too.
case 2 :
do_something_else();
break;
default :
break;
}


Also notice that the default condition is present, even though it does nothing. It is good practice to always have a default condition to show your intent. Because C allows the flow of execution to continue from one case into the next, it is also important to either have a break statement to indicate that you wish to leave the switch entirely, or to comment that you intend to flow from one case to the next.

Lately, I've also become fond of adding an extra blank line before each of the case lines (except the first, because it has a natural space on the brace line). This helps make each case line (and the default ) stand out just a little more, making the code that much more readable.

if() else if() : Braces, else if and else all aligned with the original if in the set. When it seems more logical to indent an else if() else , use the following layout instead:

if( condition )
{
}
else
{
if( another_condition )
{
}
else
{
}
}
When a sequence of if() / else if() / else if() / else has more of the sense of a switch (but with variable tests instead of the constants the case requires), then everything should align vertically in the same column, similar to a switch :-
if( cond1 )
{
}
else if( cond2 )
{
}
else if( cond3 )
{
}
else
{
}
Notice that braces are always used, even when a condition has only one line of code to execute (perhaps even no lines if you are leaving �hooks� for future features, but then a comment is generally required). This eliminates any possibility of misunderstanding between the original programmer and the maintainer. If also makes it far easier to copy new lines of code into a particular condition without requiring one to remember to add braces after the fact.

Answered by shepherd at 2:28 PM on April 17, 2008

hi pakeeza The if statement is used to select among two alternatives. It uses a boolean expression todecide which alternative should be executed. The switch statement is used to select among multiple alternatives. It uses an int expression to determine which alternativeshould be executed.
and also IF Statement: Checks the value of data is less than or greater than. (in ranges).
example: can tell wether an input age is more than 18 and less than 60.

Switch Case: Checks the value of data that is prespecified. only equal to.

example: Can only generate output if the value matches. When the age is 18 or when the age is 60 . No comarison of data based on greater than or smaller than. Compares data based on equality
for more information check source http://www.geekinterview.com/questi on_details/198

Answered by raj u at 12:08 PM on April 17, 2008

Well, although both if-else-if and switch are conditional statements, they differ a lot in the way they are used.

Some of the major differences between the two are :

1) In if-else-if , an expression is evaluated and the code is selected based on the truth value of the expression.

In switch , an expression is evaluated and the code is selected based on the value of the expression.

2) In if-else-if , Each if has its own logical expression to be evaluated as true or false.

In switch, Each case is referring back to the original value of the expression in the switch statement.

3) In if-else-if , The variables in the expression may evaluate to a value of any type, either an int or a char.

In switch , The expression must evaluate to an int.

4) There is one subtle but very important difference between the if-else-if ladder and the switch statement. That difference involves the break statement. In the if-else-if ladder, no matter what, only one of the blocks of code is executed. In the switch construct, if the break statement is omitted, the flow of execution will go forward into the next block.

Leaving out a break is sometimes useful, but pretty rare. If you are missing a break statement in any block, make sure you intended to leave it out!

For more information and example , Please visit the source site :

http://aspire.cs.uah.edu/ textbook/CPP7015.htm

Answered by Alok Gupta at 11:39 AM on April 17, 2008