What is a data types

C# - Data Types

C# is a strongly-typed language. It means we must declare the type of a variable which indicates the kind of values it is going to store such as integer, float, decimal, text, etc.

The following declares and initialized variables of different data types.

1. string stringVar = "Hello World!!";
   int intVar = 100;
   float floatVar = 10.2f;
   char charVar = 'A';
   bool boolVar = true;

C# mainly categorized data types in two types: Value types and Reference types. Value types include simple types (e.g. int, float, bool, and char), enum types, struct types, and Nullable value types. Reference types include class types, interface types, delegate types, and array types. Learn about value types and reference types in detail in the next chapter.

Predefined Data Types in C#

C# includes some predefined value types and reference types. The following table lists predefined data types:

Type	Description	Range	Suffix
byte	8-bit unsigned integer	0 to 255
sbyte	8-bit signed integer	-128 to 127
short	16-bit signed integer	-32,768 to 32,767
ushort	16-bit unsigned integer	0 to 65,535
int	32-bit signed integer	-2,147,483,648 to 2,147,483,647
uint	32-bit unsigned integer	0 to 4,294,967,295	u
long	64-bit signed integer	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	l
ulong	64-bit unsigned integer	0 to 18,446,744,073,709,551,615	ul
float	32-bit Single-precision floating-point type	-3.402823e38 to 3.402823e38	f
double	64-bit double-precision floating-point type	-1.79769313486232e308 to 1.79769313486232e308	d
decimal	128-bit decimal type for financial and monetary calculations	(+ or -)1.0 x 10e-28 to 7.9 x 10e28	m
char	16-bit single Unicode character	Any valid character, e.g. a,*, \x0058 (hex), or\u0058 (Unicode)
bool	8-bit logical true/false value	True or False
object	Base type of all other types.
string	A sequence of Unicode characters
DateTime	Represents date and time	0:00:00am 1/1/01 to 11:59:59pm 12/31/9999

As you can see in the above table that each data types (except string and object) include value range. Compiler will give an error if value goes out of datatype's permitted range. For example, int data type's range is -2,147,483,648 to 2,147,483,647. So if you assign value which is not in this range then compiler would give error.

1. // compile time error: Cannot implicitly convert type 'long' to 'int'.
   int i = 21474836470; 

Alias vs .Net Type

The above table of predefined data types are actually alias to their .NET type (CLR class) name. The following table lists alias for predefined data types and related .NET class name.

Alias	.NET Type	Type
byte	System.Byte	struct
sbyte	System.SByte	struct
int	System.Int32	struct
uint	System.UInt32	struct
short	System.Int16	struct
ushort	System.UInt16	struct
long	System.Int64	struct
ulong	System.UInt64	struct
float	System.Single	struct
double	System.Double	struct
char	System.Char	struct
bool	System.Boolean	struct
object	System.Object	Class
string	System.String	Class
decimal	System.Decimal	struct
DateTime	System.DateTime	str

Conversion

The values of certain data types are automatically converted to the different data types in C#. This is called implicit conversion.

The following is an implicit data types conversion table.

Implicit Conversion From	To
sbyte	short, int, long, float, double, decimal
byte	short, ushort, int, uint, long, ulong, float, double, decimal
short	int, long, float, double, or decimal
ushort	int, uint, long, ulong, float, double, or decimal
int	long, float, double, or decimal.
uint	long, ulong, float, double, or decimal
long	float, double, or decimal
ulong	float, double, or decimal
char	ushort, int, uint, long, ulong, float, double, or decimal
float	Double

Conversions from int, uint, long, or ulong to float and from long or ulong to double may cause a loss of precision. No data type implicitly converted to the char type. 

Conversions from int, uint, long or ulong to float and from long or ulong to double ma cause a loss of precision no data type implicitly converted to the chat type.