C Program to Swap Two Numbers

Last Updated : 18 Aug, 2026

Swapping two numbers means exchanging the values of two variables. The simplest way to swap them is by using a temporary variable.

  • First, store the value of the first variable in a temporary variable.
  • Then, assign the second value to the first variable and the temporary value to the second variable.

Illustration

Input:

a = 5, b = 10

Output:

a = 10, b = 5

Methods to Swap Two Numbers in C

The following approaches can be used to swap two numbers:

1. Using a Temporary Variable

This is the simplest approach. Store the value of the first variable in a temporary variable, then exchange the values using the temporary variable.

C 
#include <stdio.h>

int main() {
    int a = 5, b = 10, temp;

    // Swapping values of a and  b
    temp = a;
    a = b;
    b = temp;
    printf("a = %d, b = %d\n", a, b);
    return 0;
}

Output
a = 10, b = 5

Explanation

  • temp stores the original value of a.
  • The value of b is assigned to a, and the stored value in temp is assigned to b.

2. Without Using a Temporary Variable

Arithmetic operations can be used to swap two integers without an additional variable.

C 
#include <stdio.h>

int main() {
    int a = 5, b = 10;

    // Arithmetic operations to swap values
    a = a + b;
    b = a - b;
    a = a - b;
    printf("a = %d, b = %d\n", a, b);
    return 0;
}

Output
a = 10, b = 5

Explanation

  • a first stores the sum of both values.
  • Subtracting b from a gives the original value of a, and the final subtraction gives the original value of b.

Note: This method can cause integer overflow if a + b exceeds the range of int.

3. Using the Bitwise XOR Operator

For integer values, the XOR operator can swap two numbers without a temporary variable. XOR operations cancel matching bits and preserve the information needed to recover the original values.

C 
#include <stdio.h>

int main() {
    int a = 5, b = 10;

    // Apply XOR operations in the given order
    // to swap values
    a = a ^ b;
    b = a ^ b;
    a = a ^ b;
    printf("a = %d, b = %d\n", a, b);
    return 0;
}

Output
a = 10, b = 5

Explanation

  • The first XOR stores the combined bit information of a and b in a.
  • The next two XOR operations recover the original values in reversed order.

Note: The XOR method is applicable to integer types and is generally less readable than using a temporary variable.

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