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Data Types in C++: Primitive, Derived and User-defined Types

Data Types in C++: Primitive, Derived and User-defined Types

19 Feb 2024
23 min read
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Data Types in C++: An Overview

A Data Type is a classification of specific types of data by a certain value or certain types of mathematical or logical operations. Data type depends on the command of the programming language such as letters, lowercase, uppercase, numbers, punctuation, and many more. C++ Online Training will help you to understand the principles of data types C++ is essential for good programming because it determines the type, size, and behaviour of variables and enables proper data manipulation.

What is Data Type in C++?

If the question is what data type in C++ is, then it can be answered that all the variables in C++ use various data types to restrict the type of data to be stored during declaration. If a variable is defined in C++ language, then the compiler allocates some specific memory based on that particular data type.

Data types in C++ programming

There are 3 different Data types in C++, which are:
Data types in C++ programming

Primitive Data type

Primitive data types in C++ are some inbuilt data types that can be used by the user directly for the declaration of the variable. Some primitive data types in C++ are:
  1. Integer
  2. Character
  3. Boolean
  4. Floating Point
  5. Double Floating Point
  6. Valueless or Void
  7. Wide Character

1.) Integer

Integer data types represent whole numbers without a fractional or decimal part. They can be signed (positive, negative, or zero) or unsigned (only positive or zero).


int signedInt = -42;unsigned int unsignedInt = 123;

This code declares two integer variables, one signed ("signedInt") with a value of -42 and the other unsigned ("unsignedInt") with a value of 123.

2.) Character

Character data types represent individual characters from a character set, like ASCII or Unicode. In C++, `char` is commonly used to represent characters.


char myChar = 'A';

The character variable "myChar" with the value "A" is declared using this code.

3.) Boolean

Boolean data types represent binary values, typically used for true (1) or false (0) conditions. In C++, `bool` is used for Boolean data.


bool isTrue = true;
bool isFalse = false;

The two boolean variables "isTrue" and "isFalse" are declared in this code with the values true and false, respectively.

4.) Floating Point

Floating-point data types represent numbers with a fractional part. In C++, `float` is a single-precision floating-point type.


float myFloat = 3.14159f;

The floating-point variable "myFloat" is declared in this code with the value 3.14159.

5.) Double Floating Point

Double-precision floating-point data types are used to represent numbers with a larger range and higher precision compared to 'float'. In C++, 'double' is commonly used.


double myDouble = 3.141592653589793;

This code declares a high-precision double-precision floating-point variable named "myDouble" with the value of (pi).

6.) Valueless or Void

The void data type in C++ is used to indicate that a function does not return any value or to declare generic pointers that do not point to a specific data type.


void myFunction() { // This function does not return a value
void* genericPointer;

This code declares a generic void pointer named "genericPointer" as well as the void function "myFunction," which has no return value.

7.) Wide Character

Wide character data types, like 'wchar_t', are used to represent characters from extended character sets, such as Unicode characters that require more storage than a standard `char`.


wchar_t myWideChar = L'A'; // Assigning the wide character 'A'

Using the wide-character literal "L," this code declares the wide-character variable "myWideChar" with the value "A."

Read More - C++ Interview Interview Questions and Answers

Derived Data type

The derived data type in C++ is derived from the primitive data type. There are some derived data types in C++ language:
  1. Function
  2. Array
  3. Pointer
  4. Reference

1. Function

A function is a reusable block of code that performs a specific task. It is a derived data type because you can define functions to work with other data types and can even return values of different data types.


// Function that adds two integers and returns the result
int add(int a, int b) {
 return a + b;
} // Function that concatenates two strings and returns the result
std::string concatenate(std::string str1, std::string str2) {
 return str1 + str2;
} int main() {
 int sum = add(5, 3);
 std::string result = concatenate("Hello, ", "World!");
 return 0;

The main function in this code employs the two functions "add" for integer addition and "concatenate" for text concatenation, and it returns 0 as a result.

2. Array

An array is a derived data type that represents a collection of elements of the same data type, stored in contiguous memory locations. The elements can be accessed by their index.


// Declaration and initialization of an integer array
int numbers[5] = {1, 2, 3, 4, 5}; // Accessing elements of the array
int firstNumber = numbers[0]; // Accessing the first element (index 0)
int thirdNumber = numbers[2]; // Accessing the third element (index 2)

This code defines and initializes an integer array called "numbers" with values ranging from 1 to 5. It then accesses and assigns the first element to "firstNumber" and the third element to "thirdNumber" by referring to the elements' respective indices (0 and 2).

3. Pointer

A pointer is a derived data type that stores the memory address of another data type. Pointers are often used for dynamic memory allocation and for accessing memory locations directly.


// Declaration and initialization of a pointer
int* ptr; // Pointer to an integer
int num = 42;
ptr = # // Assigning the address of 'num' to 'ptr' // Accessing the value through the pointer
int value = *ptr; // Dereferencing the pointer to get the value (value = 42)

This code defines and initializes an integer pointer called "ptr," gives it the address of the integer variable "num," and then accesses the value stored at that address by dereferencing the pointer. The value 42 is then stored in the variable "value."

4. Reference

A reference is a derived data type that acts as an alias or an alternative name for an existing variable. It allows you to manipulate the original variable directly, and it cannot be null or reseated to another variable after initialization.


int originalVar = 100;
 refVar = originalVar; // Creating a reference to 'originalVar' 
 refVar = 200; // Modifying 'originalVar' through 'refVar' 
// Both 'originalVar' and 'refVar' now have the value 200

This code generates a reference variable "refVar" that references to the integer variable "originalVar" and allows adjustments through it, so updating "refVar" to 200 updates "originalVar" to 200 as well, resulting in both variables having the value 200.

Read more: Call by Value and Call by Reference in C++

User-defined or Abstract Data Type

Abstract data type in C++ language is defined by the users themselves. It is like defining a class in structure or C++. This particular data type has some variations, those are:
  1. Class
  2. Structure
  3. Union
  4. Enumeration
  5. Typedef defined Datatype

1. Class

A class is a user-defined data type that represents a blueprint for creating objects. It encapsulates data (attributes) and functions (methods) that operate on that data. Classes are used to model real-world entities and provide a way to define custom data structures.


// Define a class representing a 'Person'
class Person {
 // Attributes
 std::string name;
 int age; // Constructor
 Person(std::string n, int a) : name(n), age(a) {} // Method to display information
 void displayInfo() {
 std::cout << "Name: " << name << ", Age: " << age << std::endl;
int main() {
 // Create objects of the 'Person' class
 Person person1("Alice", 30);
 Person person2("Bob", 25); // Access and use class members
 return 0;

This code creates a class called "Person" that has attributes for name and age as well as a constructor that initializes those attributes and a method called "displayInfo" that prints out the person's data. Two "Person" objects are created, and initialized with distinct data, and their information is displayed using the "displayInfo" method in the "main" function.

Read more: Object Oriented Programming (OOPs) Concepts in C++

2. Structure

A structure is a user-defined data type that groups together variables of different data types under a single name. Structures are useful for organizing related data elements.


// Define a structure for representing a 'Point' in 2D space
struct Point {
 int x;
 int y;
int main() {
 // Create instances of the 'Point' structure
 Point p1 = {2, 3};
 Point p2 = {5, 7}; // Access structure members
 int sumX = p1.x + p2.x;
 int sumY = p1.y + p2.y; 
 return 0;

This program defines a "Point" structure to represent two-dimensional coordinates, builds two identical instances of the structure, and then computes the sums of the x and y components, storing the results in the "sumX" and "sumY" variables, respectively.

3. Union

A union is a user-defined data type that allows you to store different data types in the same memory location. Unlike structures, which allocate memory for all members, unions share memory among their members.


// Define a union representing a 'Value' that can be either an integer or a float union Value {
 int intValue;
 float floatValue;
int main() {
 // Create a union instance
 Value v; // Assign values to union members
 v.intValue = 42;
 // Now, 'v.floatValue' might not be meaningful because the same memory is shared. 
 return 0;

This code constructs a union named "Value" that can hold either an integer or a float, but because they share the same memory space, accessing one member (for example, "v.floatValue") after assigning a value to another (for example, "v.intValue") can provide unexpected results.

4. Enumeration

An enumeration is a user-defined data type that consists of a set of named integer constants. It provides a way to create symbolic names for values to improve code readability.


// Define an enumeration for days of the week
enum Days { Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday }; 
int main() {
 // Use enumeration constants
 Days today = Wednesday; 
if (today == Wednesday) {
 std::cout << "It's Wednesday!" << std::endl;
 return 0;

This code creates the "Days" enumeration, which represents the seven days of the week, assigns the value "Wednesday" to the variable "today," then checks to see if "today" equals "Wednesday," printing a message if it does.

4. Typedef Defined Data Type

typedef is a keyword that allows you to create aliases for existing data types, making your code more readable and providing abstraction. It's not a new data type but a way to create alternative names for existing ones.


 // Define a typedef for an integer pointer 
typedef int* IntPtr; 
int main() {
 int number = 42;
 IntPtr ptr = &number; // 'IntPtr' is an alias for 'int*' 
// Now, 'ptr' is equivalent to 'int*' and can be used accordingly 
return 0;

The typedef alias "IntPtr" is created by this code for an integer pointer (int*), and it is then used to declare the pointer variable "ptr," enabling it to be used as a conventional integer pointer, referring to the integer variable "number."

Datatype Modifiers in C++

In C++, data type modifiers are used to modify the behaviour and storage characteristics of basic data types. In C++, there are four modifiers. int, double, and char are the data types that can be modified using these modifiers. They are as follows:

  1. Signed
  2. Unsigned
  3. Short
  4. Long

1. Signed

The signed modifier is used to indicate that a variable can hold both positive and negative values. However, most built-in integer types (like int) are signed by default in C++. So, you rarely need to explicitly use the signed keyword.


int signedVariable = -10; // "int" is signed by default

This code declares the signed integer variable "signedVariable" with the value -10. It's vital to know that "int" is signed by default in C++.

2. Unsigned

The unsigned modifier is used to indicate that a variable can only hold non-negative values (i.e., zero or positive values). It is often used when you know that a variable should not have negative values, and you want to save memory by avoiding the storage of negative numbers.


unsigned int unsignedVariable = 20; // unsigned integer

The unsigned integer variable "unsignedVariable" is declared in this code with the value 20 and the restriction that it can only store non-negative integer values.

3. Short

The short modifier is used to indicate that a variable should be stored using fewer bits than the default data type. This is often used to save memory when you know that a variable's value will fit within a smaller range.


short shortVariable = 32767; // short integer

The maximum value that can be declared for the short integer variable "shortVariable" according to this code is 32767.

4. Long

The long modifier is used to indicate that a variable should be stored using more bits than the default data type. This is used when you need to store larger values that cannot fit within the range of a standard data type.


long long longVariable = 1234567890; // long integer

With the value 1234567890, the long integer variable "longVariable" is declared in this code.
Some basic data types of C++ programming language
Data Type Size Range
int or signed int4 Bytes-2,147,483,648 to 2,147,483,647
unsigned int4 Bytes0 to 4,294,967,295
short int 2 bytes-32,768 to 32,767
long int4 bytes -2,147,483,648 to 2,147,483,647
unsigned short int2 bytes 0 to 65,535
unsigned long int8 Bytes0 to 4,294,967,295
long long int8 Bytes-(2^63) to (2^63)-1
unsigned long long int8 Bytes0 to 18,446,744,073,709,551,615
signed char1 Bytes-128 to 127
unsigned char1 Bytes0 to 255
wchar_t2 or 4 Bytes1 wide character
float4 Bytes
double8 Bytes
long double12 Bytes

This article gives a vast overview of what is data type in C++ language including its various data types in C++ with examples. This article also covers the size of data types in C++. With this knowledge of data types,C++ certification under your belt, you're well on your way to becoming a great C++ programmer!


Q1. What are the 5 Data Types in C++?

In C++, there are five basic data types: int, float, char, bool, and double. Integers, floating-point numbers, characters, Boolean values, & double-precision floating-point numbers are each represented by one of these data types.

Q2. What is a Data Type in C++?

A data type in C++ specifies the type of data that a variable can store. The format and size of the values that can be stored in a variable are specified.

Q3. What are the uses of Data Types in C++?

In C++, data types are essential for:
  • Describing what kind of data a variable can hold.
  • Efficient memory allocation for variables.
  • Ensuring adequate data manipulation and expression and function compatibility.
  • By specifying the type of data being utilized in detail, it is possible to improve the readability and maintainability of code.
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Shailendra Chauhan (Microsoft MVP, Founder & CEO at Scholarhat by DotNetTricks)

Shailendra Chauhan is the Founder and CEO at ScholarHat by DotNetTricks which is a brand when it comes to e-Learning. He provides training and consultation over an array of technologies like Cloud, .NET, Angular, React, Node, Microservices, Containers and Mobile Apps development. He has been awarded Microsoft MVP 8th time in a row (2016-2023). He has changed many lives with his writings and unique training programs. He has a number of most sought-after books to his name which has helped job aspirants in cracking tough interviews with ease.
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