C data type_ From rookie tutorial

Value type （Value types）

Value type variables can be assigned directly to a value . They are from class System.ValueType Derived from .

Value types contain data directly . such as int、char、float, They store numbers separately 、 character 、 Floating point numbers . When you declare a int Type , The system allocates memory to store values .

The following table lists them C# 2010 Value types available in ：

type	describe	Range	Default
bool	Boolean value	True or False	False
byte	8 Bit unsigned integer	0 To 255	0
char	16 position Unicode character	U +0000 To U +ffff	‘\0’
decimal	128 The exact decimal value of ,28-29 Effective digits	(-7.9 x 1028 To 7.9 x 1028) / 100 To 28	0.0M
double	64 Bit double precision floating point	(+/-)5.0 x 10-324 To (+/-)1.7 x 10308	0.0D
float	32 Bit single precision floating point type	-3.4 x 1038 To + 3.4 x 1038	0.0F
int	32 Bit signed integer type	-2,147,483,648 To 2,147,483,647	0
long	64 Bit signed integer type	-9,223,372,036,854,775,808 To 9,223,372,036,854,775,807	0L
sbyte	8 Bit signed integer type	-128 To 127	0
short	16 Bit signed integer type	-32,768 To 32,767	0
uint	32 Bit unsigned integer type	0 To 4,294,967,295	0
ulong	64 Bit unsigned integer type	0 To 18,446,744,073,709,551,615	0
ushort	16 Bit unsigned integer type	0 To 65,535	0

To get the exact size of a type or variable on a specific platform , have access to sizeof Method . expression sizeof(type) Generates a storage size that stores objects or types in bytes . Here's an example to get... On any machine int Storage size of type ：

example

using System;

namespace DataTypeApplication
{
    
   class Program
   {
    
      static void Main(string[] args)
      {
    
         Console.WriteLine("Size of int: {0}", sizeof(int));
         Console.ReadLine();
      }
   }
}

When the above code is compiled and executed , It will produce the following results ：

Size of int: 4

Reference type （Reference types）

object （Object） type

object （Object） type yes C# General type system （Common Type System - CTS） The ultimate base class for all data types in .Object yes System.Object Alias of class . So the object （Object） Type can be assigned to any other type （ Value type 、 Reference type 、 Predefined or user-defined types ） Value . however , Before assigning values , Type conversion is required first .

When a value type is converted to an object type , It's called Packing ; On the other hand , When an object type is converted to a value type , It's called Unpacking .

object obj;
obj = 100; //  This is packing 

dynamic （Dynamic） type

You can store any type of value in a dynamic data type variable . Type checking of these variables occurs at run time .

Syntax for declaring dynamic types ：

dynamic <variable_name> = value;

for example ：

dynamic d = 20;

Dynamic types are similar to object types , But type checking of object type variables occurs at compile time , Type checking of dynamically typed variables occurs at run time .

character string （String） type

character string （String） type Allows you to assign any string value to a variable . character string （String） The type is System.String Alias of class . It is from the object （Object） Type derived . character string （String） The value of type can be assigned in two forms ： Quotation marks and @ quotes .

for example ：

String str = "runoob.com";

One @ Quote string ：

@"runoob.com";

C# string The string can be preceded by @（ Referred to as " Word for word strings "） The escape character （\） Treat as ordinary characters , such as ：

string str = @"C:\Windows";

Equivalent to ：

string str = "C:\\Windows";

@ You can wrap any line in the string , Line breaks and indented spaces are calculated within the length of the string .

string str = @"<script type=""text/javascript""> <!-- --> </script>";

User defined reference types include ：class、interface or delegate.

Pointer types （Pointer types）

Pointer type variables store another type of memory address .C# Pointer in and C or C++ Pointers in have the same function .

Syntax for declaring pointer types ：

type* identifier;

for example ：

char* cptr;
int* iptr;