define and function

now define a function,and it will be very interesting! It can change the value of a,b.

 

 1 #include <stdio.h>
 2 
 3 //liang dao yishang 
 4 #define exchange(a,b) {\
 5     int t;\
 6     t = a;\
 7     a=b;\
 8     b=t;\
 9 }
10 
11 int main()
12 {
13     int a=10,b=9;
14 
15     printf("a=%d \nb=%d\n",a,b);
16 
17     exchange(a,b);
18     printf("a=%d \nb=%d\n",a,b);
19 
20     return 0;
21 }