C Program to Swap two no’s without using third variable

#include<stdio.h>
#include<conio.h>

void main()
{
int a,b;

clrscr();

printf("\nEnter value for num1 & num2 : ");
scanf("%d %d",&a,&b);

a=a+b;
b=a-b;
a=a-b;

printf("\nAfter swapping value of a : %d",a);
printf("\nAfter swapping value of b : %d",b);

getch();
}

Output :

Enter value for num1 & num2 : 10 20

After swapping value of a : 20
After swapping value of b : 10