The Loop Constructs

The Loop Constructs:- 

          The loop directs a program to perform a set of operation again and again until a specified condition is true.

          Looping statement is used when we want to execute statement or statements until a condition is true. ‘C’ contains following type of looping statement-

• The for loop
• The while loop
• The do-while loop

For Loop:-

          For loop is used to execute a set of statement(s) for a given number of times, means if we want to execute statement(s) till a certain number of time, for loop is used.

          Syntax:-   

                             for (start value; end value; increment/decrement)

                             {

                                      Statement1;

                                      Statement2;

                             }

While Loop:-

          While loop statement contains the condition first. If the condition is satisfied, the control executes the statements of the while loop else, it ignores these statements.

          Syntax:-  

                              while (condition)

                             {

                                      Statement1;

                                      Statement2;

                             }

          Example:-

                                      #include <stdio.h>

int main()

{

int i;

i=1;

while(i<6)

{

printf(“Ouch! Please stop!\n”);

i++;

}

return(0);

}

                    Here’s what the output looks like:

                   Ouch! Please stop!

Ouch! Please stop!

Ouch! Please stop!

Ouch! Please stop!

Ouch! Please stop!

Do-While Loop:-

          Do-while loop statement is another method used in C. Do-while loop ensures that the program is executed at least once and checks whether the condition at the end of the do-while loop is true or false. As long as the test condition is true, the statements will be repeated.

          Syntax:- 

                             do

                             {

                                      Statement1;

                                      Statement2;

                             }

                             while (condition);

          Example:-

                                      #include <stdio.h>

void main()

{

int start;

printf(“Please enter the number to start\n”);

printf(“the countdown (1 to 100):”);

scanf(“%d”,&start);

/* The countdown loop */

do

{

printf(“T-minus %d\n”,start);

start--;

}

while(start>0);

printf(“Zero!\nBlast off!\n”);

return(0);

}

         

          Run the program.

Please enter the number to start

the countdown (1 to 100):

Be a traditionalist and type 10. Press Enter:

T-minus 10

T-minus 9

et cetera . . .

T-minus 1

Zero!

                             Blast off!