C # basic-variables and constants (1 ),

C # basic-variables and constants (1 ),

I. Basic concepts of variables:

Variables are used to store specific types of data and change the data values stored in variables at any time. Variables have names, types, and values. Before using a variable, you must declare the variable, that is, specify the type and name of the variable.

1. Variable type:

Variable types are defined as values and reference types.

2. Variable type;

1. Value Type:

C # simple type classification: integer, floating point, and Boolean

① INTEGER: int, sbyte, byte, short, ushort, uint, long, ulong, and char

Int type: A 32-bit signed integer with a value ranging from-2,147,483,648 ~ In the range of 2,147,483,647.

Sbyte: an 8-digit integer with a value range of 128 ~ In the range of 127.

Byte type: Unsigned 16-digit integer with a value range of 0 ~ In the range of 255.

Short: A signed 16-digit integer with a value ranging from-32,768 ~ In the range of 32,767.

Ushort: Unsigned 16-digit integer with a value ranging from 0 ~ In the range of 65,535.

Uint type: Unsigned 32-bit integer with a value range of 0 ~ In the range of 4,294,967,295.

Long: A 64-bit signed integer with a value range of 9,223,372,036,854,775,808 ~ In the range of 9,223,372,036,854,775,807.

Ulong: A 64-bit unsigned integer with a value ranging from 0 ~ In the range of 18,446,744,073,709,551,615.
Create a console application, declare the int-type variable ls, initialize it to 927, and initialize the shj variable for the byte type as 255. Output

1 statci void Main (string [] arge) 2 {3 int ls = 927; // declare an int type variable ls4 byte shj = 255; // declare a byte type variable shj5 Console. writeLine ("ls = {0}, shj = {1}" + ls, shj); // output 6 Console. readLine (); 7}View Code

If the value of shj is 266, the byte value ranges from 0 ~ 255

② Boolean:

Bool: Specifies the true or false value, which is used to store values true and false.

1 bool x = 927;View Code

Boolean data types include true and false. You can assign true or false values to a Boolean variable or an expression. The obtained value is equal to one of the two:

Bool bTest = (80> 90 );

③ Floating point type

The two data types are treated as float and double. Their difference lies in the value range and accuracy:

Float: The value range is 1.5x10 ^-45 ~ Between 3.4x10 ^ 38, the precision is 7 digits.

1 float theMySum = 9.27f; // use f to forcibly specify float Type 2 float theMySums = 1.12F; // use F to forcibly specify float TypeView Code

Double: The value range is 5.0x10 ^-324 ~ Between 1.7x10 ^ 308, precision is 15 ~ 16 digits.

1 double MyDou = 927d; // use d to forcibly convert to double2 double mudou = 112D; // use D to forcibly convert to double

2. Reference Type:

The reference type is the primary object type data for Building C # applications. The pre-defined object type creates an object instance with new and stores it in the stack.

All referred to as "classes" are reference types, including classes, interfaces, arrays, and delegation.

Create a console application, create a class C in it, create a field Value in this class, and initialize it to 0. create the reference type variable of the class through new at other locations, and finally output the variable.

1 class Program 2 {3 class C // create a class C 4 {5 public int Value = 0; // declare a public int type variable Value 6} 7 static void Main (string [] args) 8 {9 int v1 = 0; // declare an int type variable v1, and initialize it to 010 int v2 = 1; // declare an int type variable v2 and assign v1 v211 v2 = 927; // assign the variable V2 to 92712 C r1 = new C () again; // use the new keyword to create the reference object 13 C r2 = r1; // set r1 = r214 r2.Value = 112; // set the value of r2 to 15 Console. writeLine ("Values; {0}, {1}", v1, v2); // you can specify 16 Console variables for output v1 and v2. writeLine ("refs; {0}, {1}", r1.Value, r2.Value); // output the value of the reference type object 17 Console. readLine (); 18} 19}