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Choosing the Right Data Types in C++

Are you excited to explore the world of C++ programming? One important thing to consider when writing programs is choosing the right data types. In this article, we will discover why data types are important, what they are used for, and how they can be applied in real-life situations. We will also talk about multiple inheritance and what it means. So, let’s begin our journey!


When you write a program, it’s essential to choose the appropriate data types for your variables. Data types define the kind of information a variable can hold and the operations that can be performed on it. By selecting the right data type, you can optimize memory usage, improve program performance, and ensure the accuracy of your calculations.
It’s like using the right container to store and handle different types of items. Making wise choices in data types enables efficient programming and avoids potential errors or inefficiencies in your code.

Definition of Data Types

In programming, a data type determines the kind of information that can be stored in a variable. For example, if you have a variable to store true/false values, it will be of the Boolean data type. Similarly, if you want to store whole numbers, you’ll use an integer data type.

When writing code, we often need to store different types of information. Variables act as storage spaces where we keep this data. When we create a variable, we allocate some memory to hold its value. The amount of memory needed depends on the data type of the variable. For example, integers and floating-point numbers require different amounts of memory. By choosing the right data type, we can efficiently manage memory and work with different types of data in our programs.

For example,

 int score = 25;

score‘ here is an int datatype variable. The variable score can only store 2-byte or 4-byte integers, depending on the compiler/system.

The Importance of Choosing the Right Data Types

Selecting the right data type is important for several reasons:

  • Memory Efficiency: Different data types require different amounts of memory. Choosing the smallest data type that can accommodate your data helps minimize memory usage, especially when dealing with large amounts of data.
  • Accuracy: Some data types offer greater precision for numeric calculations. Using the appropriate data type ensures that your calculations are accurate and free from rounding errors.
  • Performance: Certain data types are more efficient for specific operations. Choosing the most suitable data type can improve the performance of your program by reducing unnecessary conversions or computations.
  • Code Readability: Using meaningful data types makes your code more readable and understandable to others. It enhances code maintainability and allows future developers to easily grasp the purpose and intent of your variables.

What are data types in C++?

Data types are used to define the type of data that a variable can store. C++ provides several built-in data types, including integers, floating-point numbers, characters, booleans, and more.

Data Types in C++

Primitive Data Types in C++

In C++, users can declare variables using primitive data types. These data types are built-in and come with the language itself. Examples of primitive data types include “float” for decimal numbers, “bool” for true or false values, and others.

These data types allow programmers to create variables to store specific kinds of data, like numbers with decimals or Boolean values, without needing to define them from scratch. Using these predefined data types makes it easier and more efficient to work with different types of data in C++ programs.


Integers are a data type in C++ used to store whole numbers without decimal points. They are used to represent values like 1, 2, 100, -5, etc. Integers are one of the fundamental data types in C++ and are commonly used in programming for various purposes, such as counting, indexing, and calculations.

In C++, integers can be represented using different storage sizes, such as “int” for a 4-byte integer and “short” for a 2-byte integer. The specific size of the integer depends on the compiler and system being used.

For example,

 int data = 2023;

data here is an integer data type variable. The variable data requires 2 or 4 bytes of memory space.


In C++, the keyword “char” is used to represent individual characters, like letters, digits, or symbols. For example, ‘A’, ‘7’, or ‘@’ are characters. Each “char” variable takes up 1 byte of memory, which means it can store one character at a time.

We use single quotes to enclose characters, like ‘H’ or ‘5’. This data type is helpful when you want to work with individual letters or symbols in your program.

For example,

 char ch = 'C';

ch‘ here is a character datatype variable. This means that the variable requires 1 byte of memory space.


In C++, the keyword “bool” is used for the boolean data type. It can only have two possible values: “true” or “false.” Boolean values are used to make decisions in the program, like in if-statements or loops.

For example, we can use a boolean variable to check if a condition is true or false and then execute different parts of the code based on the result. It’s a simple and essential data type for controlling the flow of a program.

For example,

 bool is_true = true;

is_true‘ here is a boolean data type variable. This means that the variable requires 1 byte of memory space.

Floating-Point Numbers

In C++, “float” is a keyword used to store numbers with decimal points, like 3.14 or 0.5. It can also handle very large or very small numbers using scientific notation, like 1.23e-5. The “float” variable can store such values and takes up 4 bytes of memory. This data type is useful when you need to work with numbers that have fractional parts or require a wide range of values.

For example,

 float val = 20.23;

val‘ here is a floating-point datatype variable. This means that the variable requires 4 bytes of memory space.

Double Floating Point

double is the keyword used to hold floating-point numbers (decimals and exponentials) with double precision. The double variable has a size of 8 bytes.

For example,

 double val = 2023.1526;

val‘ here is a double floating-point datatype variable. This means that the variable requires 8 bytes of memory space.


In C++, “void” is a special data type that represents something without a value. It is used to indicate that a function does not return any value. So, we cannot declare variables of the “void” type. Instead, we use “void” for functions that perform specific tasks without giving back any result. It’s like saying, “This function does something important, but it doesn’t produce any specific value as a result.”

 Wide Character

In C++, we have a data type called “wchar_t” which is similar to the regular “char” data type but can hold characters that require more memory. While a regular “char” can store one character and uses 1 byte of memory, “wchar_t” can store more complex characters that may need 2 or 4 bytes of memory.

It’s useful when dealing with characters from different languages or special symbols that cannot be represented using a single byte. So, if you need to handle characters that take up more memory, you can use the “wchar_t” data type in your C++ programs.

For example,

wchar_t w = L'C';

w‘  here is a wide-character datatype variable that has a value of 67 (L’C’) and a size of 4 bytes. This means that the variable requires 2 bytes or 4 bytes of memory space.

Derived Data types in C++

Derived data types in C++ are types of data that we create by combining basic or built-in data types. There are four main types of derived data types:


Functions are blocks of code that perform specific tasks. They take inputs, process them, and return outputs. Functions help in organizing code and making it reusable.


function_return_type function_name(parameters) {



 int sum(int num1, int num2) {
  return (num1 + num2);

Here, the return type of the sum function is an integer, and the function is used to calculate the sum of 2 numbers.


Arrays are collections of elements of the same data type. For example, you can create an array of integers to store a list of numbers.


datatype array_name[size_of_array];


 int arr[4]={0,1,2,3};

Here, we have defined an integer array of size 4, which can continuously store four integer variables in memory.


Pointers are variables that store memory addresses of other variables. They allow us to access and manipulate data indirectly.


data_type* variable_name;


 int* point_int;

point_int holds the address of a variable of an integer datatype.


In C++, declaring a variable as a reference means it becomes an alias for an existing variable, denoted by adding ‘&‘ to its declaration. This allows us to work with the same data using different names, making it convenient for data manipulation and function arguments.


 int val = 1526;
 int &ref = val;

Here ‘ref‘ becomes the reference to integer ‘val‘, and now any changes in one would be automatically reflected in the other as they both represent the same memory location.

User-Defined Data types in C++

The User-Defined datatype, also known as user-defined data type, is a type of data defined by the user.


In C++, a class is a fundamental component of Object-Oriented Programming. It acts as a blueprint for creating objects, which are instances of the class. A class defines its own data members (variables) and member functions (methods) that can be accessed and used when we create objects from the class. It allows us to create user-defined data types with specific attributes and behaviors, making it easier to organize and manage data in our programs.

Code Example:

#include <iostream>
using namespace std;

class Saintcoders {
    string student_name;

    void print_name() {
        cout << "Student name is: " << student_name << endl;

int main() {
    Saintcoder student1, student2;
    student1.student_name = "Coding Interview Pro";
    student2.student_name = "Saint Coders";
    return 0;


Student name is: Coding Interview Pro
Student name is: Saint Coders


  • The code defines a class called ‘Saintcoders‘ with a member variable student_name and a member function ‘print_name()‘.
  • In the ‘main()‘ function, two objects of the ‘Saintcoders‘ class, ‘student1‘ and ‘student2‘, are created.
  • The student_name attributes of both objects are set to different values.
  • Finally, the ‘print_name()‘ function is called for each object to display its names on the console.


A structure datatype is a user-defined data type that combines objects of potentially different data types into a single type.


 struct student {
     char name[12];
     char roll_no[15];
     int marks;

Here, different data types, such as an array of characters and integer data types, are combined to make a new data type according to the user’s need.


Union is a user-defined data type in C++ that combines different types of data into a single entity. Unlike structures, all members of a union share the same memory space. In the given example, we create a union called “test” that holds both an integer and a character.

The size of the union is determined by the larger data type, which in this case is the integer. Any changes made to the integer “num” will be reflected in the character “var” if we adjust “num“.


union test {
    int num;
    char var;

Here, num and var share the same memory. Therefore, if we change any variables, the changes will automatically reflect in another variable.


In C++, an enumeration (enum) is a user-defined data type used to assign names to integral constants. It makes the code easier to understand and maintain. If we don’t provide explicit integral values, the enum automatically assigns values starting from 0, similar to 0-based indexing.


enum result {pass = 90, fail = 0};

Here, we have given the integer value 90 to be ‘pass’ and 0 as ‘fail’; therefore, if we write,

enum result res;
res = pass;

Then, the value of ‘res‘ would automatically be 90.

Typedef defined DataType

In C++, typedef allows you to create new names for existing data types, making the code more readable and maintainable. It doesn’t create a new data type; it simply gives an alias to an existing one. Using typedef can improve a program’s portability as only the typedef statements need to be updated for changes. It also helps in self-documenting code by providing descriptive names for standard data types.


typedef long int LL;

Now we can use LL to define the long int data type in the code.

For Example,

LL val;
val = 123;

How are data types used in C++?

Data types are used to declare variables in C++. A variable declaration specifies the type of data that the variable can store and provides a name for the variable. For example, the following code declares an integer variable named ‘myInt‘:

int myInt;

Once a variable is declared, it can be assigned a value of the appropriate data type. For example, the following code assigns the value ‘42‘ to the ‘myInt‘ variable:

myInt = 42;

Data types are also used in function declarations and definitions. Functions can have input parameters and return values of different data types. For example, the following code declares a function named ‘add‘ that takes two integers as input parameters and returns an integer:

int add(int a, int b) {
  return a + b;

What are Data type modifiers in C++?

Data type modifiers in C++ are keywords that modify the behavior of the basic data types. They allow you to specify additional properties of variables, such as their size, range, and signedness. Some common data type modifiers in C++ include:

  • signed: Used with integer types to indicate that the variable can hold both positive and negative values.
  • unsigned: Used with integer types to indicate that the variable can only hold positive values, effectively doubling the positive range.
  • short: Reduces the size of integer types, allowing them to occupy less memory.
  • long: Increases the size of integer types, allowing them to hold larger values.
  • long long: Increases the size further to store even larger values.
  • const: Indicates that the variable’s value cannot be modified once it is assigned.
  • volatile: Indicates that the variable’s value can be changed unexpectedly by external factors, such as hardware or other threads.

These data type modifiers provide flexibility and control over the variables’ behavior, allowing programmers to optimize memory usage and define strict constraints on data manipulation.

Size and Range of Data Types

The size and range of data types in C++ can vary depending on the platform and compiler. However, the C++ language provides minimum size requirements for each data type.

Here is a table showing the minimum size requirements for some common data types in C++:

Data TypeSize (in bytes)Range
bool1true or false
char1-128 to 127 or 0 to 255
int2 or 4-32,768 to 32,767 or -2,147,483,648 to 2,147,483,647
float4Approximately ±3.4e±38
double8Approximately ±1.7e±308
Size and Range of Data Types


Data types are an essential concept in C++ programming. They allow you to specify the type of data that a variable can hold, ensuring proper memory allocation and enabling the execution of operations on that data. Understanding data types and their modifiers is crucial for writing efficient and reliable C++ programs.

In this article, we covered the commonly used data types in C++, including integers, floating-point numbers, characters, booleans, and void. We also discussed type modifiers such as ‘const‘ and ‘volatile‘, as well as the size and range of data types. Furthermore, we explored the concept of user-defined data types using structures and classes.

Having a strong understanding of data types empowers you to choose the appropriate type for your variables, optimize memory usage, and write robust C++ programs.


  • What is the importance of selecting the right data type in C++? Choosing the right data type is important as it helps optimize memory usage, improve program performance, and ensure accurate calculations.
  • How do I select the appropriate data type for my variables in C++? To select the appropriate data type, consider the range and precision of values your variable needs to hold. Use built-in data types like int, float, or double based on your program’s requirements.
  • Can I change the data type of a variable in C++? Yes, you can change the data type of a variable by casting or converting it. However, be cautious about the potential loss of precision or unexpected behavior when converting between different data types.
  • What are the consequences of using an inappropriate data type in C++? Using an inappropriate data type can result in wasted memory, reduced program performance, and inaccurate calculations. It may also lead to unexpected errors or limitations when working with different data types.
  • Are there any specific guidelines for choosing data types in C++? It’s important to understand the range and behavior of each data type in C++. Consider the size, precision, and specific requirements of your program. Following best practices and considering your program’s needs will help you choose the most suitable data types in C++.

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