Review the C-language bit operations

0X01: Bitwise AND (&)

Role:

1) Clear Zero. If you want a cell to be zeroed, even if all of its bits are 0

2) Take some of the points in a number to locate. Those positions that are about to want 1.

Example: If you have an integer a (2 bytes), you want the low byte, just A and (377,8 = = 00000000 11111111) bitwise and can be.

3) which one to keep, with a number & operation, this number in this bit takes 1.

0X02: Bitwise OR (|)

Role:

Often used to set the value of some bits of a data 1, example: A (16-bit integer), a|0377, low 8-bit full 1, high 8-bit remains the same

0x03: xor (^)

Role:

1) Flip the specific bit

Suppose there are 01111010, want to make it low 4-bit flip, that is, 1 to change 0,0 1,. It can be performed with the 00001111 ^ operation.

2) with 0-phase ^ retain original value

3) Exchange two values without temporary variables

Suppose a=3,b=4

A=a^b;

B=b^a;

A=a^b;

0X03: Take the reverse (~)

Role:

For an integer, if you want the lowest one to be 0, you can use a a=a&~1; with better consistency (the ~ operator precedence is higher than the arithmetic operator, the relational operator, the logical operator, and other operators)

0X03: Shift Left (<<)

Role:

High-left shift after overflow, discard.

Generally used to take low

0X04: Right Shift (>>)

Role:

Lower right shift is discarded, on unsigned number, high 0

Generally used to take low

Shift right one is equivalent to dividing by 2, right shift n is equivalent to dividing by 2 n times

Note: When you move right, you need to be aware of the problem with the sign bit. For unsigned numbers, the left high position is shifted to 0 for the signed number, if the original sign bit is 0 (the number is positive), the left is also moved in 0, if the sign bit is 1 (that is, negative), then the left-hand side is 0 or 1, depending on the computer system.

Review the C-language bit operations