Binary source code, inverse code, complement code

Catalog

Binary has original code 、 Inverse code 、 The existence form of complement

1、 Original code

2、 Inverse code

3、 Complement code

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First , We need to know Computers only recognize 0、1 code , That is what we call binary .

therefore , All the data in the computer is based on Binary complement The form , And participate in the operation .

Then why should we use complement form ？, What is the complement ？

Binary has original code 、 Inverse code 、 The existence form of complement

1、 Original code

Because there are positive numbers 、 Existence of negative numbers , So the computer needs to judge the symbol of the stored number when storing , In the computer , The sign bit of a positive number is 0, The sign bit of a negative number is 1.

for example ：byte 1 The original code of = 00000001    -1 The original code of = 10000001 

1  - 1 = ？ Calculate with binary .

In the computer Only adders exist , therefore 1 - 1 === 1 +（-1） Convert to binary

00000001
10000001
10000010 = -2 

1 - 1 = -2 This value is obviously wrong , To solve this problem , There's an irony .

2、 Inverse code

The inverse code is changed on the basis of the original code , The inverse of a positive number is the same as the original , The inverse code of a negative number is the original code Except the sign bit Conduct Take the opposite .

for example ：1 The inverse of = 1 The original code of = 00000001  -1 The inverse of = 11111110

00000001
11111110
11111111   Inverse code 
10000000  -0  Original code 

According to the inverse code operation 1 - 1 = -0 , Then there is right in the inverse code 0 Two expressions -0 10000000  and 0 00000000, There is also ambiguity , therefore , There's a complement .

3、 Complement code

Complement is to transform again on the basis of inverse code , The original code of a positive number 、 Inverse code 、 Complement is the same form , The complement of a negative number is based on the inverse +1 .

for example ：-1 Complement = 11111110 + 1 = 11111111

00000001
11111111
00000000 0  Complement code    Create spillover , The highest position is rounded off   
                  The original code of a positive number 、 Inverse code 、 The complement is the same 

So get 1 - 1 = 0 The only correct result of .

therefore , The binary in the computer participates in the operation and storage in the form of complement .