位xxxx学会了麽？

#include <iostream>
using namespace std;

#define HALF_BITS_LENGTH 4
#define FULLMASK 255 //1111 1111
#define LMASK ((FULLMASK)<<(HALF_BITS_LENGTH))//1111 0000
#define RMASK ((FULLMASK)>>(HALF_BITS_LENGTH))//0000 1111
#define RSET(c,n) (c=((c&LMASK)^n))
#define LSET(c,n) (c=((c&RMASK)^(n<<HALF_BITS_LENGTH)))
#define RGET(c) (RMASK&c)
#define LGET(c) ((LMASK&c)>>HALF_BITS_LENGTH)
#define GRIDW 3

int main()
{
unsigned char c;

for (LSET(c,1);LGET(c)<(GRIDW*GRIDW);LSET(c,(LGET(c)+1)))
   for (RSET(c,1);RGET(c)<GRIDW*GRIDW;RSET(c,RGET(c)+1))
   {
    if ((LGET(c)%GRIDW)!=(RGET(c)%GRIDW))
    {
     cout<<"A = "<<RGET(c);
     cout<<"B = "<<LGET(c);
    }
    cout<<endl;
   }
   system("pause");

}