Shift operation of complement

Usually , In the computer Signed number With Complement code stored .
Deep understanding of complement

Shift the complement left ： Removed bit complement 0.
The sign bit may also change , Thus, the positive and negative numbers change .
stay When there is no sign bit change , Moving one bit to the left is equivalent to $\times 2$. Special , When the number is negative , This property also holds ：

Suppose the number in the computer 8bit Storage ：

Complement code	Original code	Count
0111 1000	0111 1000	120
1111 0000	1001 0000	-16
1110 0000	1010 0000	-32
1100 0000	1100 0000	-64
1000 0000	Cannot be expressed in the original code	-128
0000 0000	0000 0000	0

The limit value of left shift is 0.

Shift the complement right ：

• Yes just Integers （ Symbol bit 0） Move right ： Removed bits repair 0
• Yes negative Integers （ Symbol bit 1） Move right ： Removed bits repair 1, The result is still negative

The limit value of the right shift of a positive integer is 0, The limit value of the right shift of negative integers is -1.

in fact , When it's negative , When moving right, the highest position is filled 0 Or make up 1 Depending on the rules of the compilation system .（ repair 0 Of is called “ Logical shift right ”, repair 1 Of is called “ Arithmetic shift right ”.） therefore , Try not to shift negative numbers ！

Be careful ：
Whether arithmetic shift right or logical shift right , The result of the operation Is the original number divided by 2. For unsigned numbers , Logical shift right is adopted （ repair 0）; For signed Numbers , Using arithmetic shift right . When arithmetic moves right , The number of the left complement sign bit .