Understanding C# Data Types: Value Types, Reference Types, and Pointer Types

Explore C#'s data types—value types, reference types, and pointer types—understanding their characteristics, memory management, and how to choose the appropriate data type for your variables. This guide clarifies the differences between value and reference types and their implications for program behavior.

Understanding C# Data Types

Introduction to Data Types

In C#, a data type specifies what kind of data a variable can hold (e.g., numbers, text, true/false values). Choosing the correct data type is crucial because it impacts memory usage, the range of values a variable can store, and the operations you can perform on that data. C# has three main categories of data types.

Value Types

Value types store their data directly within the variable. When you assign a value type variable to another, a copy of the data is created. Changes to one copy don't affect the other.

Predefined Value Types

These types are built into the C# language:

  • Integer Types: sbyte, short, int, long (signed); byte, ushort, uint, ulong (unsigned)
  • Floating-Point Types: float, double, decimal
  • Character Type: char
  • Boolean Type: bool

User-Defined Value Types

You can create your own value types using structs and enums.

Type Size (32-bit) Range
char 1 byte 0 to 65,535
sbyte 1 byte -128 to 127
byte 1 byte 0 to 255
short 2 bytes -32,768 to 32,767
ushort 2 bytes 0 to 65,535
int 4 bytes -2,147,483,648 to 2,147,483,647
uint 4 bytes 0 to 4,294,967,295
long 8 bytes -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
ulong 8 bytes 0 to 18,446,744,073,709,551,615
float 4 bytes Approximately ±1.5 × 10−45 to ±3.4 × 1038
double 8 bytes Approximately ±5.0 × 10−324 to ±1.7 × 10308
decimal 16 bytes At least 28-29 significant digits

Note that the memory size of some types might vary slightly depending on the system architecture (32-bit vs. 64-bit).

Reference Types

Reference types store a reference (memory address) to the data. When you assign a reference type to another variable, both variables point to the same data. Changes made through one variable are reflected in the other.

Predefined Reference Types

  • object
  • string

User-Defined Reference Types

  • Classes
  • Interfaces

Pointer Types

Pointer types store the memory address of a variable. They're less commonly used in C# (compared to C or C++). You use the asterisk (*) to declare a pointer. The ampersand (&) is the address-of operator; the asterisk (*) is the dereference operator.

Example Pointer Declaration

int* myIntPtr; // Pointer to an integer