two's complement (two's complement) 1. in computer systems, values ​​are always represented (stored) in two's complement. the main reason: using complement code, the sign bit and other bits can be processed uniformly; at the same time, subtraction can also be processed as addition. in addition, when two numbers expressed in two's complement are added, if there is a carry in the highest bit (sign bit), the carry is discarded. 2. the conversion process of complement code and original code is almost the same.

for example

1111 1111                          255
− 0101 1111                         −  95
===========                         =====
  1010 0000  (反码ones' complement)   160
+         1                          +   1
===========                          =====
  1010 0001  (补码two's complement)     161