C Data Types Explained: int, float, char, and More – A Complete Guide

C Data Types

This tutorial demystifies the fundamental data types in C—int, float, char, and others—so you can write precise, efficient code.

Video: Data Types in C Programming

In C, every variable is declared with a data type that defines its size and value range. For example:

int myVar;

Here, myVar is an int (integer) variable, typically occupying 4 bytes.

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Basic Types

Below is a quick reference for the most commonly used C data types.

Type	Size (bytes)	Format Specifier
int	at least 2, usually 4	%d, %i
char	1	%c
float	4	%f
double	8	%lf
short int	2 usually	%hd
unsigned int	at least 2, usually 4	%u
long int	at least 4, usually 8	%ld, %li
long long int	at least 8	%lld, %lli
unsigned long int	at least 4	%lu
unsigned long long int	at least 8	%llu
signed char	1	%c
unsigned char	1	%c
long double	at least 10, usually 12 or 16	%Lf

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int

An int represents whole numbers—zero, positives, and negatives—without decimal points. Typical examples include 0, -5, and 10.

Declare an integer variable like this:

int id;

The variable id now holds an integer. You can also declare multiple integers simultaneously:

int id, age;

On most platforms, int is 4 bytes (32 bits) and can represent 2³² distinct values ranging from –2,147,483,648 to 2,147,483,647.

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float and double

Use float and double to store real (floating‑point) numbers.

float salary;
double price;

Both types support scientific notation, e.g.,

float normalizationFactor = 22.442e2;

Key difference: float (single precision) occupies 4 bytes, whereas double (double precision) occupies 8 bytes.

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char

The char keyword declares a single character variable. Example:

char test = 'h';

Its size is exactly 1 byte.

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void

void represents the absence of type. It’s used for functions that return no value:

void printMessage() {
    printf("Hello, world!\n");
}

You cannot create variables of type void.

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short and long

When you need a larger numeric range, use long or long long:

long a;
long long b;
long double c;

For small integer ranges (–32,767 to 32,767), short suffices:

short d;

Check a type’s size with sizeof():

#include <stdio.h>
int main() {
    short a;
    long b;
    long long c;
    long double d;

    printf("size of short = %d bytes\n", sizeof(a));
    printf("size of long = %d bytes\n", sizeof(b));
    printf("size of long long = %d bytes\n", sizeof(c));
    printf("size of long double= %d bytes\n", sizeof(d));
    return 0;
}

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signed and unsigned

Modifiers that control a type’s value range:

• signed – allows negative and positive values.
• unsigned – restricts to non‑negative values only.

Examples:

// valid
unsigned int x = 35;
int y = -35;  // signed int
int z = 36;   // signed int

// invalid – unsigned cannot hold negative numbers
unsigned int num = -35;

With a 4‑byte int, y spans –2³¹ to 2³¹‑1, while x spans 0 to 2³²‑1.

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Derived Data Types

Derived types build on fundamental types: arrays, pointers, structures, and functions. Further tutorials will cover these in depth.

• bool type
• Enumerated type
• Complex types