Loops in C Programming Language

What is loop?

In computer programming, a loop is a sequence of instructions that is continuously repeat until a certain condition is reached.

There are two types of loops in C Programming:

Entry Controlled loops: In Entry controlled loops the test condition is checked before entering the main body of the loop. For Loop and While Loop is Entry-controlled loops.

Exit Controlled loops: In Exit controlled loops the test condition is evaluated at the end of the loop body. The loop body will execute at least once, irrespective of whether the condition is true or false. do-while Loop is Exit Controlled loop.

For Loop

for loop in C programming is a repetition control structure that allows programmers to write a loop that will be executed a specific number of times. for loop enables programmers to perform n number of steps together in a single line.

Syntax:

for (initialize expression; test expression; update expression)
{
    //
    // body of for loop
    //
}

Example:

#include <stdio.h>

int main()

{

  int i = 0;

  for (i = 1; i <= 10; i++)

  {

    printf( "Hello ICSK\n"); 

  }

  return 0;

}

Algorithm:

step-1: start the program.

Step-2: set i = 0

step-3: check i <= 10, if true go to step-4, if false go to step-6

step-4: print ICSK

step-5: i++, go to step-3

step-6: stop the program

While Loop

While loop does not depend upon the number of iterations. In for loop the number of iterations was previously known to us but in the While loop, the execution is terminated on the basis of the test condition. If the test condition will become false then it will break from the while loop else body will be executed.

Syntax:

initialization_expression;

while (test_expression)

{    

    update_expression;

}

Example:

#include <stdio.h>

  

int main()

{

  // Initialization expression

  int i = 2;

  

  // Test expression

  while(i < 10)

  {

    // loop body

    printf( "Hello ICSK\n");  

     

    // update expression

    i++;

  }

   

  return 0;

}

do-while Loop

The do-while loop is similar to a while loop but the only difference lies in the do-while loop test condition which is tested at the end of the body. In the do-while loop, the loop body will execute at least once irrespective of the test condition.

Syntax:

initialization_expression;

do

{

    // body of do-while loop

    

    

    update_expression;

} while (test_expression);

Example:

#include <stdio.h>

  

// Driver code

int main()

{

  // Initialization expression

  int i = 2;

   

  do

  {

    // loop body

    printf( "Hello ICSK\n");  

  

    // Update expression

    i++;

     

    // Test expression

  }  while (i < 1);  

   

  return 0;

}

Source: https://www.geeksforgeeks.org/c-loops/