(original) C # learning Note 04--Process Control 01--boolean logic 02--bitwise operator

4.1.2 Bitwise operators

& and | Operators also have a role in performing operations on numeric values. When used in this way, they deal with a series of bits stored in a variable, rather than variable values, so they are called bitwise operators.

Let's discuss & and | below. The & operator each bit in the first operand is compared to a bit in the same position in the second operand, and in the resulting result, the bits in each position are shown in table 4-5.

| Operators are similar, but the resulting bits are different. As shown in table 4-6.

　　

The use of the ^ operator is the same as this. If there is a bit in the same position in the operand and only one is 1, the result bit is 1, as shown in table 4-7.

　　

You can also use the unary operator ~ in C #, which will reverse the bits in the operand, and the result should be a bit of 1 in the operand, 0 in the result, and vice versa, as shown in table 4-8.

　　

Integers are stored in the. NET is called 2 of the complement, even with the unary operator ~ will make the results look a bit odd. Assuming that the int type is a 32-bit number, the operator ~ operates on all 32 bits, which will help to see this way. For example, the full binary representation of the number 5 is:

000000000000000000000000000000101

The full binary representation of the number-5 is:

111111111111111111111111111111011

In fact, according to the 2 complement system, (-X) is defined as (~x+1). This system is very useful when adding numbers together. For example, the binary representation of adding 10 and 5 together (that is, subtracting 5 from 10) is:

000000000000000000000000000001010

+ 111111111111111111111111111111011

= 1000000000000000000000000000000101

Note: Ignoring the left-most 1, you get a binary representation of 5. A ~1=2 like this is odd because the underlying structure forces the result to be generated.

In addition to the 4 bitwise operators, this section describes the other two operators, as shown in table 4-10.

　　

These operators, often referred to as displacement operators, are best illustrated with a simple example:

int var1, var2 = ten, var3 = 2;

var1 = Var2 << var3;

As a result, the value of Varl is 40. The procedure is as follows: The binary value of 10 is 1010, the value is shifted to the left by two bits, and 101000 is the 40 in decimal. In fact, a multiplication operation was performed. move each bit to the left, multiply the number by 2, so move the two-bit to the left, and multiply the original operand by 4 (2 * 2). moving one bit to the right divides the operand by 2 and discards the non-integer remainder :

int var1, var2 = 10;

var1 = var2 >> 1;

In this example, the value of VAR1 is 5, and the following code gets the value 2:

int var1, var2 = 10;

var1 = var2 >> 2;

In most code, these operators are not used, but you should be aware of the existence of such operators. They are primarily used in highly optimized code , where no other mathematical operations are used. Therefore, they are typically used for device drivers or system code.

The displacement operator also has an assignment operator, as shown in table 4-11.

　　

(original) C # learning Note 04--Process Control 01--boolean logic 02--bitwise operator