In C Programing, A loop is a repeating of statement until a specific condition is satisfied. There are  mainly three types of loops are used in C language.  

  • for loop
  • while loop
  • do...while loop

for loop

Syntax of for loop :

for (initialization Statement; test condition; increment of Statement)
{
    // statements of loop
}

This is loop which is used frequently in c Language.

Flow Diagram of For loop

Decision Making and Looping

Note : In C language, we can not declare the variable in condition and We can initialize more than one variable in Expression .

Step 1: In Initialization expression we initialize the loop variable to some values. e.g. int i=1.

Step 2: If the test condition is evaluated and test condition is evaluated to false, the for loop is terminated.
Step 3: If the test expression successful executed in loop body and variable incremented or decremented, depending on the operation (++ or –).

Step 4: Again the test condition is evaluated .

Example : Find the sum of first n natural numbers (for loop)

// find the sum of first n natural numbers

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

    printf("Enter a positive integer: ");
    scanf("%d", &num);

    // for loop terminates when num is less than count
    for(count = 1; count <= num; ++count)
    {
        sum += count;
    }

    printf("Sum = %d", sum);

    return 0;
}

Output:

Enter a positive integer: 10
Sum = 55