two's complement 1. In the Calculator machine system, the number value is always represented (stored) by a complement. The main reason: Use complement, which can be used to unify notation bits with other bits; subtractive can also be handled as addition. In addition, when two complementary numbers are added and the notation bit has a carry, the carry is discarded. 2, complement and source code conversions process is almost the same.

Example

1111 1111 255
− 0101 1111 − 95
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1010 0000 (ones' complement) 160
Plus one plus one
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1010 0001 (two's complement) 161