C for loop

 For Loop

For loop is used to execute a set of statements repeatedly until a particular condition is satisfied. It is known as an open ended loop.

Syntax 

for(initialization; test condition; increment/decrement) 

{

block of statements;

} 

 

 

How for loop works?

• The initialization statement is executed only once.
• Then, the test expression is evaluated. If the test expression is evaluated to false, the for loop is terminated.
• However, if the test expression is evaluated to true, statements inside the body of the  for loop are executed, and the update expression is updated.
• Again the test expression is evaluated.

This process goes on until the test expression is false. When the test expression is false, the loop terminates.

Example 

To calculate sum of first N natural numbers

#include <stdio.h>
#include <conio.h>
void main()
{
    int num, count, sum = 0;

    printf("\n Enter a positive integer: ");
    scanf("%d", &num);
    for(count = 1; count <= num; count++)
    {
        sum += count;
    }

    printf("\n Sum = %d", sum);

    getch();
}

Output

 

Nested For Loop

 We can also have nested for loops, i.e one for loop inside another for loop. 

Syntax 

 for(initialization; test condition; increment/decrement) 

   {

        for(initialization; test condition; increment/decrement)

          { 

             block of statements; 

         }

} 

Example 

#include<stdio.h>
#include <conio.h>
void main( )
{
    int i, j;
    for(i = 1; i < 5; i++)
    {
        printf("\n");
        for(j = i; j > 0; j--)
        {
            printf("\t %d", j);
        }
    }
    getch();
}

Output