[embedded C foundation] Part 5: original code / inverse code / complement code

1 Concept

 Original code
A positive number = Inverse code = Complement code
 Inverse code
negative ： The sign bits remain the same , Reverse the value bit
 Complement code
negative ： Counter code plus 1 Get the complement

2 How signed numbers are stored in memory

Signed numbers are converted into binary complements in memory for storage , Unsigned numbers are directly converted to binary storage .

Convert to inverse code , The sign bits remain the same .

Signed number representation 3 Kind of ： Original code 、 Inverse code 、 Complement code
constitute ： Sign bit + The numerical part consists of
Sign bit ：1 negative 0 just

Example 1： The signed number in memory is 1001 0110, What is the corresponding decimal number ？

Be careful ： Is a signed number , And the sign bit is 1, Negative numbers , be 1001 0110 Complement this number
So the inverse of the number is 1001 0101, The original code of this number is 1110 1010, namely -106
summary ： Signed numbers are stored in memory as complements
Unsigned numbers are directly converted into binary storage in memory

Example 2：

analysis ：int Type defaults to the signed type , Signed types are stored in memory in the form of complements ,-1 The complement of is 1111 1111 1111 1111, The first output is zero -1, The second is unsigned , Store in original code in memory , So it is 216-1=65535