Hello World

In this part of the tutorial, we will write our first Fortran program: the ubiquitous Hello World example.

However before we can write our program, we need to ensure that we have a Fortran compiler set up.

Compiler setup

In this tutorial, we’ll work with the free and open source GNU Fortran compiler (gfortran), which is part of the GNU Compiler Colection (GCC).

To install gfortran on Linux, use your system package manager. On macOS, you can install gfortran using Homebrew or MacPorts. On Windows, you can get native binaries here.

To check if you have gfortran setup correctly, open a terminal and run the following command :

$> gfortran --version

this should output something like:

GNU Fortran 7.5.0
Copyright (C) 2017 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Hello world

Once you have setup up your compiler, open a new file in your favourite code editor and enter the following:

program hello
  ! This is a comment line, it is ignored by the compiler
  print *, 'Hello, World!'
end program hello

Having saved your program to hello.f90, compile at the command line with:

$> gfortran hello.f90 -o hello

To run your compiled program:

$> ./hello
Hello, World!

Congratulations you’ve written, compiled and run your first Fortran program! In the next part of this tutorial we will introduce variables for storing data.