How Do I Print Double Data Type in C++?


Larry Thompson

Printing a double data type in C++ can be achieved using the cout statement from the iostream library. The double data type is used to represent decimal numbers with a higher precision compared to float. To print a double value, follow the steps below:

Step 1: Include iostream Library

To use the cout statement, you need to include the iostream library at the beginning of your program. This can be done by adding the following line of code:

#include <iostream>

Step 2: Declare and Initialize a Double Variable

In C++, you need to declare and initialize a variable before using it. To declare and initialize a double variable, you can use the following syntax:

double myDouble = 3.14159;

Step 3: Print the Double Value

To print the value of a double variable, you can use the cout statement followed by the insertion operator (<<). Here’s an example:

std::cout << myDouble;

The above code will output:


Tips for Formatting Double Output

If you want to control the formatting of your double output, you can make use of various manipulators provided by the iomanip library.

  • Precision Manipulator:
    • The setprecision(n) manipulator sets the decimal precision to n.
  • Fixed Manipulator:
    • The fixed manipulator forces the output to be displayed with a fixed number of decimal places.
  • Showpoint Manipulator:
    • The showpoint manipulator shows trailing zeros for decimal values.

To use these manipulators, you need to include the iomanip library:

#include <iomanip>

Here’s an example that demonstrates the usage of these manipulators:

#include <iostream>
#include <iomanip>

int main()
  double myDouble = 3.14159;
  std::cout << std::setprecision(3) << std::fixed << std::showpoint;
  std::cout << myDouble;
  return 0;

The above code will output:



In this tutorial, we learned how to print a double data type in C++. We used the cout statement from the iostream library and explored how to format the output using various manipulators from the iomanip library. Now you can confidently print double values in your C++ programs!

I hope this tutorial was helpful. Happy coding!

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