C # Variables and expressions

Name of the variable:

The first character must be a letter, underscore, or @;

The subsequent characters can be letters, underscores, or numbers.

Note: Case sensitive.

Types of variables:

• Numeric type

1. Integer type

BYTE, short, int, long

SByte, ushort, uint, Unlong

2. Floating-point number type

float, double, decimal

• Simple Type

char, BOOL, string

Number of bytes in the account:

Variable declaration:

int myinteger=17;
String mystring= "Hello world!";
Console.WriteLine ("{0} {1}", Myinteger, myString);

Escape characters:

The operators mainly include:

• Arithmetic operators
• Assignment operators
• Relational operators
• logical operators
• Conditional operations
• Bitwise manipulation Operators
• The string operator.

An expression is a combination of operators and operands, such as a*b+1-c.

The expressions mainly include:

• An arithmetic expression
• An assignment expression
• Conditional expressions
• Boolean expressions, etc.

Arithmetic operators and expressions

C # provides five operators: the "+" addition operator, the "-" subtraction operator, the "*" multiplication operator, the "/" division operator, and the "%" modulo operator. The precedence of arithmetic operators is calculated in the order in which they are multiplication and then added and reduced.

Assignment operators and expressions

Assigning a value is giving a new value to a variable. The assignment operators in C # are: =, + =,-=, *,/=,%=, &=, |=, >>=, <<=, ^=.

In C #, variables are allowed to be continuously assigned, such as A=b=c.

The binding of the assignment operator is from right to left combined, so a=b=c is equivalent to A= (b=c).

relational operators and expressions

A relational operator is actually a "judge" symbol with the result of true (true) or False (false).

logical operators and expressions

C # consists of three logical operators: "With (&&)", "or (| | ) "," Non-(! ）”。

Which, "!" The operator is a single-mesh operator, meaning it has only one operand.

Their operands are expressions of a Boolean or Boolean value, and the operation result is a Boolean value of "true" or "false".

Bitwise operators

The bitwise operators can be divided into shift operators and logical bits operators. Any information in the computer is stored in binary form, and the bitwise operator is the operator that operates on the data in binary order.

The operators in C # include ">>", "<<", "^", "&", "|", "~".

Attention:

 for (&&,| |), the object of the operation is a logical value, which is true/false  && equivalent to Chinese and, | |  True  && true = && False = false  && True = && False =
     
       True 
      | | True = | | False = | | True = | | False = False 

 for (&,|), the object of the operation is a bit, that is, 1/0   1  & 1  = 1  1  & 0  = 0  0  & 1  = 0  0  & 0  = 0  1  | 1  = 1  1  | 0  = 1  0  | 1  = 1  0 | 0 = 0< /span> 

Self-increment and decrement operators

j=i++: First assigns I to the J;i plus 1;

J=++i:i first add 1, then assign the value to J;

Conditional operators

Syntax: variable name = (condition)? value 1: Value 2.

Run: If the condition is true, then the conditional expression evaluates to a, otherwise the value is B.

Comma operator

The general form of a comma expression is: expression 1, Expression 2

The order of execution of the comma expression is: first solve expression 1, then solve Expression 2. The value of the entire comma expression is the value of expression 2. For example, the expression "1+2,3+4", the value of the comma expression is 7.

Operator precedence level

Priority level	Operator
From high to Low	+ + 、--(prefix); +,-(unary)
	*、/、%
	+,-
	=, *=,/=,%=, + =,-=
	+ + 、--(suffix)

C # Variables and expressions