X+Y=5=00000101
反码01111111-00000101=01111010
补码01111010+1=01111011=120
X-Y=25=00011001
反码=01111111-00011001=01100110
补码=01100110+1=01100111=103.
X+Y=5=00000101
反码01111111-00000101=01111010
补码01111010+1=01111011=120
X-Y=25=00011001
反码=01111111-00011001=01100110
补码=01100110+1=01100111=103.