C Data Types

Summary: in this tutorial, you’ll learn about the C data types, including basic types, derived types, enumeration, and void.

Introduction to the C data types

In C, an object refers to a memory location where its content represents a value. If you assign an object a name, that object becomes a variable.

A data type determines the number of bytes allocated to a variable and valid operations that you can perform.

C provides the basic types, derived types, enumeration type, and void:

Note that this tutorial provides you with an overview of C data types. And you’ll learn each of them in detail in the next tutorials. It’s fine if you don’t understand fully.

Basic types in C

C has some basic types:

• char – a single byte that can hold one character.
• int – integer type.
• float – single-precision floating-point type.
• double – double-precision floating-point type.

char

The char type can hold a single character. To form a literal character, you use the single quotes ('). For example:

char ch = 'A';
Code language: C++ (cpp)

int

To represent the integers, C uses the int keyword:

int n = 100;

C has some qualifiers that can apply to the integers. For example, you can use the short and long qualifiers for integers like this:

short int quantity;
long int counter;
Code language: C++ (cpp)

The short and long qualifiers change the sizes of integers. The int keyword can be omitted in the declaration:

short quantity;
long counter;
Code language: C++ (cpp)

The signed and unsigned qualifiers may be applied to integers. The unsigned numbers always zero or positive:

unsigned int quantity; // quantity cannot be negative
Code language: C++ (cpp)

float

The float type stores a single precision floating-point number:

float pi = 3.14;
Code language: C++ (cpp)

double

The double type stores a double-precision floating point number:

double price = 9.99;
Code language: C++ (cpp)

Typically, the number of bytes of a double is as twice as the number of bytes of a float.

Boolean

C doesn’t support the Boolean type natively. Instead, it uses integers to represent boolean values. All non-zero numbers are true while zero is false.

To make it more convenient working with boolean values, C defines the bool and a pair of constants true and false in the stdbool.h standard library. For example:

#include <stdio.h>
#include <stdbool.h>

int main()
{
    bool active = false,
         status = true;

    return 0;
}
Code language: C++ (cpp)

Derived types

The derived types in C are arrays, pointers, struct, and union.

Array

An array is a list of elements with the same type. For example, you can have an array of integers:

int numbers[] = {1, 2, 3};
Code language: C++ (cpp)

Pointer

A pointer is a variable that stores the address of an other variable. Suppose, you have a variable n:

int n = 0;
Code language: C++ (cpp)

The address of n is &n. To define a pointer that stores the address of n, you use the indirection operator (*):

int *pn = &n;
Code language: C++ (cpp)

By using the pointer, you can manipulate the variable n indirectly. For example, you can assign a value to n by using the pointer like this:

*pn = 10;
Code language: C++ (cpp)

The value of n now is 10.

Struct

A struct can contain multiple variables of different types. For example, you can define a struct person that has the first_name, last_name, and age:

struct person 
{
    char first_name[25];
    char last_name[25];
    unsigned age;
}
Code language: C++ (cpp)

Enum type

Enumeration is a list of named integer constants. The following example defines a list of statuses: open, assigned, and fixed. They correspond to the integer 1, 2, and 3.

enum STATUS
{
    open = 1,
    assigned = 2,
    fixed = 3
};
enum STATUS bug_status = open;
Code language: C++ (cpp)

void

The void is an empty type. When a function doesn’t return any value, you can use the void type. For example:

void say(char* something);
Code language: C++ (cpp)

Summary

• The basic types in C are char, int, float, and double.
• C uses integers to represent boolean values. Nonzero numbers are true, while zero is false.
• Derived types include array, pointer, struct, and union.
• An enumeration is a list of named integer constants.
• The void type is an empty type.