Variables and Data Types

C# Variables and Data Types

C# variables store data values, and each variable has a data type that determines the type of data it can hold and how much memory it uses. C# is a strongly typed language, meaning every variable must have a defined type.

Value Types (Stored in the stack)

Value types directly store data. Below are the value types, their sizes in memory, and ranges.

Type	Bytes	Range	Example
byte	1	0 to 255	byte b = 255;
sbyte	1	-128 to 127	sbyte sb = -128;
short	2	-32,768 to 32,767	short s = -1000;
ushort	2	0 to 65,535	ushort us = 50000;
int	4	-2,147,483,648 to 2,147,483,647	int i = 123;
uint	4	0 to 4,294,967,295	uint ui = 4000000000;
long	8	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	long l = 900000;
ulong	8	0 to 18,446,744,073,709,551,615	ulong ul = 123456789;
float	4	±1.5 × 10⁻⁴⁵ to ±3.4 × 10³⁸	float f = 3.14f;
double	8	±5.0 × 10⁻³²⁴ to ±1.7 × 10³⁰⁸	double d = 3.14159;
decimal	16	±1.0 × 10⁻²⁸ to ±7.9 × 10²⁸	decimal dec = 1000.99m;
char	2	Unicode characters (U+0000 to U+FFFF)	char c = 'A';
bool	1 (true/false)	N/A	bool isTrue = true;

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Reference Types (Stored in the heap)

Reference types store a reference to the data's location in memory.

Type	Description	Example
string	A sequence of characters	string name = "Alice";
object	Base type of all types	object obj = 42;
dynamic	Type resolved at runtime	dynamic dyn = "text"; dyn = 123;

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Default Values

If variables are not explicitly initialized, they take default values.

Type	Default Value
int	0
float	0.0f
bool	false
string	null
object	null

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Examples

1. Numeric Types

int age = 25;
float pi = 3.14f;
decimal salary = 55000.75m;
Console.WriteLine($"Age: {age}, Pi: {pi}, Salary: {salary}");

2. Boolean and Char

bool isComplete = true;
char initial = 'A';
Console.WriteLine($"Complete: {isComplete}, Initial: {initial}");

3. Strings and Objects

string name = "John Doe";
object anyValue = 42;
Console.WriteLine($"Name: {name}, Object: {anyValue}");

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Summary

• Value Types: Stored in the stack, directly hold data (e.g., int, float, bool).
• Reference Types: Stored in the heap, hold references to data (e.g., string, object).
• Default Values: Variables get defaults like 0 for numbers and null for references.
• Memory Efficiency: Choose types like float or decimal based on precision needs.