Iteration Statements Also called Loops or looping statements

The iteration statements allow a set of instructions to be performed repeatedly until a certain condition is fulfilled. The iteration statements are also called loops or looping statements in C++.

C++ provides three types of loops

• For Loop
• While Loop
• Do-while Loop

The for Loop

The for loop is the sassiest to understand of C++ loops. All its loops-controls elements are gathered in one place (on top of the loop),while in the other loop construction in C++, they are scattered about the program. The general form (syntax) of the for loop statement is

for( initialization expression(s) ; test-expression ; update expression(s) )

body of the loop  ;

Below is an example.

Program to Print 1 to 10 numbers using Loop

The while Loop

The second loop available in C++ is the while loop. The while loop is an entry-controlled loop. The syntax of a while loop is

While(expression)

Loop body

Where the loop body may contain a single statement, a compound statements or an empty statement. The loop iterates while the expression evaluates to true. When the expression becomes false, the program control passes to the line after he loop-body code.

In a while loop, a loop control variable should be initialized before the loop begins as an uninitialized variable can be used in an expression. The loop variable should be updated inside the body of the while.

Below is an example.

Program to calculate factorial of an Integer using While loop

The do-while Loop

Unlike the for and while loops, the do while is an exit controlled loop i.e. it evaluates its test expression at the bottom of the loop after executing its loop-body statements. This means that a do-while loop always executes at least once, even when the test expression evaluates to false initially.

The syntax of the do while loop is

Do

 { statement ; }

While (test-expression) ;

The braces {} are not necessary when the loop body contains a single statement.

The following example prints all upper cases

Char ch=”A” ;

Do

 { cout<<”/n”<<ch

Ch++; }

While (ch<=Z) ;

The above loop prints characters from ‘A’ onward until the condition ch<=Z becomes false.