The highest bit of 87 is 1, which is a negative number; The complement of negative numbers is different from the complement of positive numbers. So something went wrong. put int a = 0x 8765432 1； Change to unsigned a = 0x87654321; ，put char * ch =(char *)&； a； Changed to unsigned char * ch = (unsigned char *)&; a； The correct way is to make them unsigned numbers and avoid participating in the complement process.