C program to calculate the sum of odd and even numbers

C program to calculate the sum of odd and even numbers - Source code

#include <stdio.h>
 
int main()
{
    int i, n;
    int sum_odd = 0, sum_even = 0;
 
    printf("Enter the number up to which you want to calculate sum\n");
    scanf("%d", &n);
    for (i = 1; i <= n; i++)
    {
        // to check whether number is odd or even
        if (i % 2 == 0)
            sum_even = sum_even + i;
        else
            sum_odd = sum_odd + i;
    }
    printf("Sum of all even numbers  = %d\n", sum_even);
    printf("Sum of all odd numbers = %d\n", sum_odd);
}

Program Output

Case 1:

Enter the number up to which you want to calculate sum
100
Sum of all even numbers  = 2550
Sum of all odd numbers = 2500

Case 2:

Enter the number up to which you want to calculate sum
25
Sum of all even numbers  = 156
Sum of all odd numbers = 169

Program Explanation

1. Two integer variables i and n are declared. Two integer variables sum_odd and sum_even are declared and initialized to 0.

2. For loop starts the first iteration with 1 and continue up to the number entered by the user (n).

3. To check whether the number in the current iteration is even or odd, modulus operator (%) is used. This operator divides the number by 2 and returns the remainder. If reminder returned is 0, the number is even otherwise it is odd.

4. The value of sum_even and sum_odd operators is updated inside the loop and printed when the loop ends.