C Program to Add Two Integers

Last Updated : 18 Aug, 2026

Adding two integers in C combines two values to produce their sum. The + operator provides the simplest way to perform this operation.

  • C also allows addition using increment and bitwise operations.
  • These approaches demonstrate different ways to perform the same operation.

Illustration

Input: a = 5, b = 3
Output: 8
Explanation: The sum of 5 and 3 is 8.

Input: a = -2, b = 7
Output: 5
Explanation: The sum of -2 and 7 is 5.

Approaches to Add Two Integers

The following approaches can be used to add two integers:

1. Using the + Operator

The + operator directly adds two integer values and returns their sum.

  • It works with both integers and floating-point numbers.
  • The result is stored in a variable or printed directly.
C 
#include <stdio.h>

int main() {
    int a, b, sum = 0;
  
  	// Read two numbers from the user
    printf("Enter two integers: ");
    scanf("%d %d", &a, &b);

    // Calculate the addition of a and b
    // using '+' operator
    sum = a + b;

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

    return 0;
}

Output

Enter two integers: 5 3
Sum: 8

Explanation: The program reads two integers, adds them using the + operator, and stores the result in sum.

2. Using the Increment Operator

The ++ operator can be used to add a value repeatedly. For a positive b, a is incremented b times; for a negative b, it is decremented accordingly.

C 
#include <stdio.h>

int main() {
    int a, b;

    printf("Enter two integers: ");
    scanf("%d %d", &a, &b);

    if (b >= 0) {
        for (int i = 0; i < b; i++)
            a++;
    }
    else {
        for (int i = 0; i > b; i--)
            a--;
    }

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

    return 0;
}

Output

Enter two integers: 5 3
Sum = 8

Explanation: The program repeatedly increments or decrements a based on the value of b, resulting in a + b.

3. Using Bitwise Operators

Addition can also be performed without the + operator using XOR and AND operations.

Approach

  • XOR (^) adds the bits without considering the carry.
  • AND (&) identifies the carry bits.
  • Left shift (<<) moves the carry to the next position.
  • The process repeats until no carry remains.
C 
#include <stdio.h>

int main() {
    int a, b;

    printf("Enter two integers: ");
    scanf("%d %d", &a, &b);

    while (b != 0) {
        int carry = a & b;
        a = a ^ b;
        b = carry << 1;
    }

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

    return 0;
}

Output

Enter two integers: 5 3
Sum = 8

Explanation: a ^ b calculates the sum without carry, while a & b identifies the carry. Shifting the carry left by one position and repeating the process produces the final sum.

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