csapp 练习2.59

#include <stdio.h>
#include<limits.h>
/* return last byte of x or other bytes of y*/
unsigned bytefun(unsigned x,unsigned y)
{
    return ((x<<24)>>24)|(y&(UINT_MAX-0xff));
}
int main()
{
    unsigned x = 0x89ABCDEF;
    unsigned y = 0x76543210;
    printf("%x",bytefun(x,y));
    return 0;
}