What is C++ Double?


Google (and other such browsers like Mozilla Firefox) have become inseparable parts of our life. Even hardly literate people can use Google these days. 

Can you believe that in the IT world where professionals are racing to learn the programming languages like Python, R, and Java, your favorite Google Chrome is built on C++?

C++ is mistakenly thought of as an outdated language. 

Did You Know?

According to the TIOBE index, in the list of most popular programming languages, C++ is at 4th position.

When you need to build high-performance applications, you use C++. Some of the most popular high-performance applications such as Mozilla Firefox, Adobe products, Phyre Engine, Unreal, Unity Engine are all built on C++ and are utilized by most firms that are related to video gaming.

Also, C++ is used to create Chromium-based browsers, MySQL, and Microsoft Office and in the development of most popular operating systems including Apple’s macOS and Microsoft Windows. 

Due to its versatility and quick performance, C++ is in demand in 2021. The median annual salary of a C++ Developer is around USD 104,000 and may go as high as USD 150,000, according to the data by ZipRecruiter.

Today we will learn the special features of C++ including c++ double and the ways you can use it.

What is C++?

Developed in 1979 by Bjarne Stroustrup, C++ is an object-oriented programming language that possesses features of both high-level and low-level languages. Keeping ‘classes’ in mind, C++ was developed as C with Classes and hence the name, which means C plus One. 

The language comes along with very useful features that make it a versatile language to be used in the development of high-performance applications.

Some special features of C++ include:

  • Simple (easy to use)
  • Portable (allows to run the code on different operating systems)
  • Object-Oriented Programming (everything is treated as an object, thus allowing for inheritance and polymorphism)
  • Mid-level Programming Language (includes features of low-level and high-level languages)
  • Rich Library support
  • Compiler-based (requires no interpretation, thus faster performance than languages like Java)
  • Case sensitive (it has a different meaning for upper-case and lower-case letters)
  • Recursion
  • Dynamic Memory Allocation
  • Fast

What is C++ Double?

There are three predominant categories of data types in C++ namely Primary, Derived, and User-defined. Primary data types or primitive data types in C++ are inbuilt in the language. 

C++ Double is a data type that comes under primitive data type. This is a versatile data type meant for holding any numeric value, particularly decimal values or floating-point numbers. This can hold decimal numbers up to 15 digits. 

While working with numbers that have huge decimal points, programmers use Double as a default data type. You can declare a variable as double just by adding the keyword ‘double’ as a prefix to it. 

Syntax of Double

To declare a variable as double, the syntax is 

double variable_name;

Remember to keep the keyword double in lower-case.

double var1, var2;


double var1 = 2.33333;

double var2 = 3.0;

double var3 = 9;

double var4 = -9.88888

Working of Double Data Type in C++

The working pattern of double data type is interesting and efficient, which is why it is the favorite of almost all C++ programmers. Let’s see how the double data type works.

  • It is specifically meant to hold floating-point values that may have up to 15 digits to fill the space of 8 bytes in the memory.
  • The value of data that a double data type can store may range from 1.7E – 308 to 1.7E + 308
  • The C++ compiler considers every value as double and performs type conversion between different data types implicitly. 
  • When you need results to precision, you can use a double data type. It also prevents the loss of data with significant digits. 

Rules for using Double in C++

There are no strict rules for using double data types in C++. Indeed, there are some rules to make the code look cleaner and enable the user to understand the double data type. These are:

  • It is important to note that C++ double must have floating-point up to 15 places because it contains double the precision of the data type ‘float’.
  • While declaring a variable as double, remember to initialize it with a decimal value. For instance, you have a decimal number 2.0. If you initialize it as 2, it will still work properly because 2.0 and 2 are identical. But there is a difference in their intrinsic presentation.
  • Both the values should be of double data type while performing operations such as division or multiplication. There are chances of data loss if you don’t do so.
  • While initializing a variable in float data type, you are required to append f in the end; if you don’t append f, it is by default considered as double data type. 
  • When you write as:
  • float a = 2.66f this is considered as float data type.
  • float a = 2.66 this is considered as double data type.

An Example of Double Data Type

Program: To change the given temperature from Celsius to Fahrenheit

#include <iostream>

using namespace std;

int main()


double  c_temp, f_temp;

cout << “Take an input in celsius and then convert it into fahrenheit:”;

cin >>  c_temp;

f_temp = (c_temp * 1.8) + 32;

cout << “temperature in Fahrenheit is :” << f_temp;

return 0;


This takes Celsius temperature as input and gives Fahrenheit as output. 


I hope this article has made the double data type in C++ clear to you. 

To master the concepts of C++, there are many online courses offered by accredited institutes. These courses allow you to learn at your own pace, choose your preferred mode of learning, have doubt sessions at the end, an enterprise-class learning management system, and round-the-clock learners’ assistance. 

The best part of these online courses is that you get career guidance at the end of the course. 

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