Introduction

Def:- Executing a set of statements repeatedly for some number of times or until some condition or event.

Ex:- print numbers between 1 to 20 without loops.

            void main()

            {

                        printf(“1”);

                        printf(“2”);

                        printf(“3”);

                        printf(“4”);

                        .

.          

.

                        printf(“20”);

            }

The same printf() statement has to be repeated 20 times to print the numbers. To avoid this type of complexities, Loops were introduced.

Executing a set of statements repeatedly some number of times or until some condition, is called looping. In looping, sequences of statements are executed until some conditions for termination of the loop are satisfied. A program loop therefore consists of two Segments: Body of the loop and Control statements. The control statement tests certain conditions and then directs the repeated execution of the statements contained in the body of the loop.

The Test may be either to determine whether the loop has been repeated the specified number of times (Counter controlled loops) or to determine whether a particular condition or event has been met (Event controlled loops).

In looping process in general would include the following four steps

1. Setting and initialization of a counter i.e. loop control variable
2. Exertion of the statements in the loop
3. Test for a specified conditions for the execution of the loop
4. Incrementing the counter

C language provides 3 loop structures

1. While Loop

            Repeats a statement or group of statements while a given condition is true. It tests the condition before executing the loop body.

2. do-while Loop 

It is like a while statement, except that it tests the condition at the end of the loop  body.

3. for Loop 

It is a repetition control structure that allows you to efficiently write a loop that needs to execute a specific number of times.