Working with Data Types in C

In this lesson, you will learn

Data Types in C Language

Data Types in C

Data types define the type of data a variable can hold.

It helps the compiler to understand how much memory to allocate and how to interpret the stored data.

1. Primary/Basic Data Types

Type	Size (Bytes)*	Description	Example
`int`	2 or 4	Stores integers	`int a = 10;`
`float`	4	Stores decimal numbers (single precision)	`float b = 3.14;`
`double`	8	Stores decimal numbers (double precision)	`double d = 3.14159;`
`char`	1	Stores a single character	`char ch = 'A';`

2. Derived Data Types

Type	Description	Example
Array	Collection of elements of same data type	`int arr[5];`
Pointer	Stores memory address of another variable	`int *p = &a;`
Function	A block of code performing a task	`int sum(int x, int y)`

3. User-Defined Data Types

Type	Description	Example
struct	Collection of variables of different types	`struct Student {int id; char name[20];}`
union	Similar to struct, but shared memory	`union Data {int i; float f;}`
enum	Set of named integer constants	`enum days {SUN, MON, TUE};`
typedef	Rename existing data type	`typedef int marks;`

Additional Type Modifiers

To further control the range and memory of variables, C provides modifiers:

Modifier	Used With	Effect
`short`	`int`	Reduces size
`long`	`int`, `double`	Increases size
`signed`	`int`, `char`	Allows negative and positive
`unsigned`	`int`, `char`	Allows only positive

Example:

short int s;       // Smaller range
long int l;        // Larger range
unsigned int u;    // Only positive integers

Summary Table: Primary Data Types in C with Modifiers

Data Type	Size (Bytes)	Range (Approx.)	Description
`char`	1	–128 to 127	Stores single character (signed by default)
`signed char`	1	–128 to 127	Explicitly signed character
`unsigned char`	1	0 to 255	Only positive characters
`int`	4	–2,147,483,648 to 2,147,483,647	Default integer
`signed int`	4	–2,147,483,648 to 2,147,483,647	Same as `int`
`unsigned int`	4	0 to 4,294,967,295	No negative integers
`short int`	2	–32,768 to 32,767	Short integer
`unsigned short int`	2	0 to 65,535	Positive short integer
`long int`	4 or 8	–2,147,483,648 to 2,147,483,647 or more	Larger integer
`unsigned long int`	4 or 8	0 to 4,294,967,295 or more	Positive long integer
`long long int`	8	–9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	Very large integers
`unsigned long long int`	8	0 to 18,446,744,073,709,551,615	Very large positive integers
`float`	4	±3.4 × 10^–38 to ±3.4 × 10^38	Single precision real number
`double`	8	±1.7 × 10^–308 to ±1.7 × 10^308	Double precision real number
`long double`	10 or 12	±1.1 × 10^–4932 to ±1.1 × 10^4932	Extended precision real number

Notes:

char is typically signed by default but may vary based on compiler.
Use unsigned when negative numbers are not needed — allows larger positive values.
Use long and long long when handling large integer values.
float, double, and long double are for decimal values, use double if more precision is needed.

Example Code Using Various Data Types:

#include<stdio.h>
int main() {
    int age = 25;
    float pi = 3.14;
    char grade = 'A';
    double bigNumber = 123456.789;
    
    printf("Age: %d\n", age);
    printf("Pi: %.2f\n", pi);
    printf("Grade: %c\n", grade);
    printf("Big Number: %.3lf\n", bigNumber);
    return 0;
}

Curriculum

Learn C Programming

Chapter 0: Getting Started With C

Chapter 1: Introduction to C Programming

Basic Syntax and Control Structures