2.

typedef unsigned char *byte_pointer;

void show_bytes(byte_pointer start, size_t len) {

　　int i;

　　for (i=0;i<len;i++)

　　　　printf(" %.2x",start[i];

　　printf("\n");

}

void inplace_swap(int *x,int *y) {

　　*y = *x^*y;

　　*x = *x^*y;

　　*y = *x^*y;

}

computer systems work from a programmer's perspective