as for i know their are two different logics for the 
swapping techinque.... swapping is a type of techinque used 
for interchanging the two varibles in the operating 
memory....
1) using only variables
2) using EX-OR operator '^' 
first logic only know.
 void main()
{
int a,b;
printf("enter the a&b");
scanf("%d%d",&a,&b);
a+=b;
b=a-b;
a-=b;
printf("a=%d\nb=%d",a,b);
getch();
}

One more method its bit complicated from the people from 
the non electronics background......
void main()
{
   pf(" a and b ");
   sf("%d %d", &a, &b);
   a= a^b;
   b= b^a;
   a= a^b;
   pf("Swapped no's are a=%d and b=%d" ,a ,b);
}

You can swap two Numbers without using temporary variable 
with the help of EX-OR operator;

#include<stdio.h>
#include<conio.h>
void main()
{
 int a,b;
 clrscr(); 
 printf("Enter the first No.:");
 scanf("%d",&a);
 printf("Enter the second No.:");
 scanf("%d",&b);
 a^=b^=a^=b;
 printf("%d %d",a,b);
 getch();
}

as far i know i know two logics they are
first one
void main()
{
int a,b;
printf("eneter any two values");
scanf("%d%d",&a,&b);
a=a+b;
b=a-b;
a=a-b;
printf("a=%d\nb=%d",a,b);
getch():
}
second one 
void main()
{
int a,b;
printf("eneter any two values");
scanf("%d%d",&a,&b);
a=a*b;
b=a/b;
a=a/b;
printf("a=%d\nb=%d",a,b);
getch():
}

three logic
xor -> a^=b^=a^=b;
addition and subtraction,
multiply and division .......

in 7 types