C# - Data Types

Data types specify the type of data that a valid C# variable can hold. C# is a strongly-typed language. It means we must declare the type of a variable that indicates the kind of values it is going to store, such as integer, float, decimal, text, etc.

There are 3 types of data types in C# language.

Types	Data Types
Value Data Type	short, int, char, float, double, struct, enum, null
Reference Data Type	String, Class, Object,  Interface and array
Pointer Data Type	Pointers

 

 1. Value Data Types

Value data types hold the actual data in memory. These types include numbers, characters, booleans, and so on. C# supports both signed and unsigned versions of numeric types.

There are two kinds of value data types:

🔸 a) Predefined Data Types:

These are built-in types like int, char, float, double, etc. Here is a table showing their memory size and value range

 

Data Type	Size in C#	Value Range	Notes
byte	1 byte	0 to 255	Unsigned integer
sbyte	1 byte	-128 to 127	Signed integer
short	2 bytes	-32,768 to 32,767	Signed 16-bit integer
ushort	2 bytes	0 to 65,535	Unsigned 16-bit integer
int	4 bytes	-2,147,483,648 to 2,147,483,647	Signed 32-bit integer
uint	4 bytes	0 to 4,294,967,295	Unsigned 32-bit integer
long	8 bytes	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	Signed 64-bit integer
ulong	8 bytes	0 to 18,446,744,073,709,551,615	Unsigned 64-bit integer
float	4 bytes	±1.5×10⁻⁴⁵ to ±3.4×10³⁸	Single-precision, ~7 digits accuracy
double	8 bytes	±5.0×10⁻³²⁴ to ±1.7×10³⁰⁸	Double-precision, ~15–16 digits accuracy
decimal	16 bytes	±1.0×10⁻²⁸ to ±7.9×10²⁸	High precision (28–29 digits), good for financial calculations
char	2 bytes	Unicode U+0000 to U+FFFF	Stores a single Unicode character
bool	1 byte (typically)	true or false	Represents Boolean values; size depends on implementation

int myNum = 5;               // Integer (whole number)

double myDoubleNum = 5.99D;  // Floating point number

char myLetter = 'D';         // Character

bool myBool = true;          // Boolean

string myText = "Hello";     // String

2) User defined Data Types

Structure: Structure (struct) is a value type that groups related variables. It can also include methods and constructors.

struct Coordinate

 {

public int x;

public int y;

}

enum: enum (or enumeration type) is used to assign constant names to a group of numeric integer values. It makes constant values more readable, for example, WeekDays.Monday is more readable then number 0 when referring to the day in a week.

An enum is defined using the enum keyword, directly inside a namespace, class, or structure. All the constant names can be declared inside the curly brackets and separated by a comma.

Example:

enum WeekDays

{

Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday

 }

2. Reference Data Types

Reference types don’t store the actual data but store a reference (or address) pointing to the data's memory location. If you change the value using one variable, the change reflects in all references to that data.

There are two categories:

• Predefined types: like string, object

• User-defined types: like class, interface

Example:

string myText = "Hello";    // Reference type

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 3. Pointer Data Types

A pointer is a special type that stores the memory address of another variable. Pointers are mostly used in unsafe code blocks in C#.

Symbols used in pointer

Symbol	Name	Description
& (ampersand sign)	Address operator	Determine the address of a variable.
* (asterisk sign)	Indirection operator	Access the value of an address.

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Declaring a pointer

The pointer in C# language can be declared using * (asterisk symbol).

1.      int * a;  //pointer to int      

2.      char * c; //pointer to char