Notes – Data Types in C++

A data type in C++ tells the compiler what kind of data a variable can hold.

Each variable in C++ must be declared with a specific type before use.

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Why Are Data Types Important?

• Help the compiler allocate memory correctly
• Define what kind of operations can be performed on the variable
• Prevent type-related errors during compilation

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Categories of Data Types in C++

Category	Description
Primary (Built-in)	Basic types like int, char, float, etc.
Derived	Based on built-in types, e.g., arrays, pointers, functions
User-defined	Created by the user, e.g., struct, class, enum
Void	Represents absence of value, mostly used in functions

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1. Primary (Built-in) Data Types

Type	Size (Typical)	Description	Example
int	4 bytes	Stores integers	int age = 25;
char	1 byte	Stores single character	char grade = 'A';
float	4 bytes	Stores decimal numbers	float pi = 3.14;
double	8 bytes	More precise decimal	double area = 12.456;
bool	1 byte	Stores true/false	bool isValid = true;

Sizes may vary slightly depending on compiler and system architecture.

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2. Derived Data Types

Type	Description
Array	Collection of elements of same type
Pointer	Stores memory address of a variable
Function	Function declaration or pointer to function
Reference	Alias for another variable

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3. User-defined Data Types

Type	Purpose
struct	Group of variables of different types
class	Object-oriented data structure
enum	Defines a set of named integer constants
union	Shares memory among its members
typedef	Creates an alias for existing data type

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4. Void Data Type

• Used when a function does not return a value.

void greet() {
    cout << "Hello!" << endl;
}

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Modifiers with Data Types

Modifier	Used With	Purpose
signed	int, char	Can store positive and negative values
unsigned	int, char	Only positive values (increases range)
short	int	Smaller integer size
long	int, double	Larger size and range

Example:

unsigned int x = 100;
long double bigValue = 123456.7890;