Fortran makes it quite easy to add subroutines/functions from other languages like C/C++. Below is a short example on how to rewrite the Hello world example in C++ then run it from a Fortran script. See documentation at the bottom of the page to learn how to do it the other way around, implementing Fortran functions in C++ code
First we write the function hello() in C++. Create a .cpp file and name it "sub" (short for subroutine) . Below is an example of the code to put in sub.cpp. Feel free to modify the function declaration.
#include <iostream>
extern "C" void hello(); #This line is needed for the main function to recognize the hello() function
void hello()
{
std::cout << "Hello World" << std::endl;
return;
}
Now we may create the main file. Start by creating a blank f.90 file and name it "main" Add the following code
program main
implicit none
! Declare C/C++ function.
interface
subroutine hello() bind (c)
end subroutine
end interface
! Call C/C++ function.
call hello()
end program
Now try running the project. Try changing the hello() function and play around with the interface in main. To check your understanding .
For further reading on how to implement C++ in Fortran (and vice versa) Check this