The source code is a binary fixed-point notation, that is, the highest bit is the notation bit, "0" is positive, "1" is negative, and the rest of the bits are magnitude.

Negative code: positive number negative code and the original code is the same; negative number inverts its source code bit by bit, except for the notation bit. Complement: The positive number is the same as the original code. The negative number complement adds 1 to the end of its negative code.