On C # Learning experience--data type

One of the technical books I've read is written in this way:

"Object-oriented programming absorbs the essence of structured programming and combines it with some new concepts, resulting in a different and better way to organize programs." In most cases, the program has two organizational methods: the code (the object that performs the action) is centered or the data (the affected object) is centered. Programs are typically organized as code-centric when programming using only a structured approach. This approach can be thought of as "code for Data".

Object-oriented programs use a different approach, which organizes programs in a data-centric way, and its key principles are "data-control access to code." In object-oriented languages, data and the corresponding code that acts on that data are defined, so data types are used to precisely define the operations that apply to that data. "   

--excerpt from the c#4.0 full reference Manual (US) Herbert Schildt

C # is a strongly typed language, and all operations are checked by the compiler type, and illegal operations are not compiled, which helps prevent errors and enhance the reliability of the program. In C #, all variables, expressions, and values have their type.

C # divides data types into two kinds: value types and reference types .

The difference between the two types is what the variable holds. For a value type, the variable holds the actual value, and for the reference type, it is a reference to the value that is saved.

In C #, all data types are defined in a platform-independent manner for future C # and. NET migrations to other platforms

1. Value type: C # consists of 13 types of values, often referred to as simple types or basic types.

1) Integer: There are 8 predefined types of shaping. As the following table:

name	CTS Type	Description	Range
SByte	System.SByte	8-bit signed integer	-128~127 ( -2^7~2^7-1)
Short	System.Int16	16-bit signed short integer	-32768~32767 ( -2^15~2^15-1)
Int	System.Int32	32-bit signed integer	-2147483648~2147483647 ( -2^31~2^31-1)
Long	System.Int64	64-bit signed long integer	-9223372036854775808~9223372036854775807 ( -2^64~2^64-1)
Byte	System.Byte	8-bit unsigned shaping	0~255 (0~2^8-1)
UShort	System.UInt16	16-bit unsigned short integer	0~65535 (0~2^16)
UInt	System.UInt32	32-bit unsigned integer	0~4294967295 (0~2^32-1)
ULong	System.UInt64	64-bit unsigned long integer	0~18446744073709551615 (0~2^64-1)

C # defines the signed and unsigned forms of various integral types. The difference between a signed integer and an unsigned integer is in how the integer higher order bit is handled. For signed integers, the compiler generates code that takes the higher-order bits of an integer as a sign bit, 0 for integrity, and 1 for negative values.

2) floating-point type: Divided into single-and double-precision values. As the following table:

name	CTS Type	Description	Number of digits	Range
Float	System.Single	32-bit single-precision floating-point number	7	1.5e-45~3.4e+38
Double	System.Double	64-bit double-precision floating-point number	15/16	5e-324~1.7e+308

If a non-integer value is hard-coded in code, the compiler assumes that the variable is double, and if you want to specify that the value is float, you can add the character F (or F) after it. For example: float f=12.5f

3) Decimal type: A floating-point number that represents a higher precision, as in the following table:

name	CTS Type	Description	Number of digits	Range
Decimal	System.Decimal	128-bit high-precision decimal number representation	28	1e-28~7.9e+28

This type is mostly used for financial calculations, not basic types, so there is a performance penalty for using that type in the calculation.

If you want to make the number a decimal type, you can add the character m (or m) after the number. Example: Decimal d=12.60m

4) BOOL Type: Used to contain a Boolean value of TRUE or false, as in the following table:

name	CTS Type	Description	Number of digits	value
bool	System.Boolean	Represents true or False	NA	True or False

NOTE: BOOL values and integers cannot be implicitly converted, and if a variable (or a function's return type) is declared as a bool type, only the value TRUE or false can be used. If you attempt to use 0 to indicate false, a value other than 0 indicates true, an error occurs. 5) Character type: In order to save a single character value, as in the following table:

name	CTS Type	value
Char	System.Char	Represents a 16-bit (Unicode) character

Note: The literal of the char type is enclosed in single quotation marks, and if the character is placed in double quotation marks, the compiler will treat it as a string, resulting in an error.

In addition to char representing character literals, you can also use 4-bit hexadecimal Unicode values, integer values with data type conversions, or hexadecimal numbers to represent them. They can also be represented by escape sequences.

6) C # also defines other three kinds of value types: Enumeration (enum), struct (struct), and nullable type.

2. Reference type: C # supports two predefined reference types, such as the following table:

name	CTS Type	Description
Object	System.Object	Root type, other types in the CTS are derived from it (including value types)
String	System.String	Unicode string

1) Object type: In C #, the object type is the final parent type, and all built-in types and user-defined types derive from it.

2) String Type:

Although the assignment of a string type is like an assignment of a value type, string is a reference type.

There are some differences between string and reference type, such as: the string is immutable. Modifying one of the strings creates a completely new string object, and the other string has no change.

String literals are placed in double quotation marks.

On C # Learning experience--data type