Data Types

Predefined Data Types

C# provides 15 predefined types they include 13 simple types and 2 non-simple types.
The names of all the predefined types consist of all lowercase characters. The predefined
Simple types include the following:

• 11 numeric types, including
• Various lengths of signed and unsigned integer types.
• Floating-point types—float and double.

A high-precision decimal type called decimal. Unlike float and double, type decimal can represent decimal fractional numbers exactly. It is often used for monetary calculations.

• A Unicode character type, called char.
• A Boolean type, called bool.

 Type bool represents Boolean values and must be one of two values—either true or false.

The two non-simple types are the following:

• Type string, which is a sequence of Unicode characters.
• Type object, which is the type on which all other types are based.

 

 

 

 

 

 

The predefined simple types with their lengths.

The Predefined Non-Simple Types

User-Defined Types
Besides the 15 predefined types provide by C#, you can also create your own types, called userdefined types.
There are six kinds of types you can create, as follows:

• Types are created using a type declaration, which includes the following information:

• The kind of type you are creating
• The name of the new type

A declaration (name and specification) of each of the type’s members—except for array
and delegate types, which do not have named members Once you have declared a type, you can create and use objects of the type just as if they were predefined types. But whereas using predefined types is a one-step process in which you simply instantiate the objects, using user-defined types is a two-step process. You first declare the type and then instantiate objects of the type.