Data Types in C

A data type tells C what kind of value a variable will store. It also affects the operations that can be performed and the amount of memory used.

Basic data types

Type	Stores	Example	Typical use
char	one character	char grade=’A’;	letters/symbols
int	whole number	int age=20;	count, age, marks
float	decimal value	float price=25.5f;	decimal values
double	more precision decimal	double pi=3.14159;	scientific/precise values
void	no value	void display(void);	functions with no return value

Derived and user-defined types

Array – stores multiple values of the same type.
Pointer – stores an address in memory.
Structure (struct) – groups related values of different types.
Union – different members share the same memory area.
Enumeration (enum) – creates named integer constants.

sizeof operator

#include <stdio.h>

int main() {
printf(“int = %zu bytes\n”, sizeof(int));
printf(“char = %zu bytes\n”, sizeof(char));
printf(“float = %zu bytes\n”, sizeof(float));
printf(“double = %zu bytes\n”, sizeof(double));
return 0;
}

The exact size of some types can depend on the compiler and platform, so sizeof is the correct way to check the size on your system.

📝 EXAM POINT: Do not assume every C data type has exactly the same size on every computer.