**C Program to swap two numbers without using third variable:** To implement swapping of numbers but without using the third variable for this we need to perform some basic mathematical operations.

**How to swap two numbers without using a third variable?**

For swapping number first we have two numbers and without using the third variable we swap numbers by doing a simple mathematical operation (sum and subtract )

**Steps for swapping of two numbers**

Let us assume variable a, b

1. Add the first and second numbers and store addition in the first variable.

a = a + b

2. Subtract the first and second numbers and store them in the second variable.

b = a – b

3. Subtract the first and second numbers and store them in the first variable.

a = a – b

**Example:**

a = 10, b = 20;

a = 10+20 => a= 30

b = 30-20 => b = 10

a = 30-10 => a=20

Result a = 20, b = 10;

## C Program to swap two numbers without using third variable

#include<stdio.h> void main() { int first,second ; printf("Enter first\n"); scanf("%d",&first); printf("Enter second\n"); scanf("%d",&second); printf("before swaping\n first =%d \n second =%d\n"first, second); first = first + second; second = first - second; first = first - second; printf(" after swaping\n first=%d\n second=%d",first,second); }

**Output:**