Fortran

Fortran is a language with a focus on numerical computing. It is the oldset commonly used computer programming language and today is primarily found in eastablished numerical applications. In the HPC domain it is useful to have a least a basic Fortran knowledge for working with long-established solvers or numerical libraries. Although there are modern version of Fortran it has lost popularity in HPC to c, c++ (often Python wrapped) and Julia. It is still regarded as a high performance language and continues to be supported by high performance tooling and drivers.

The Fortran language specification has rarely changed over time but several changes have been significant. Fortran77 can still be seen in numerical codes, with Fortran90 also being common. ‘Modern Fortran’ refers to more recent versions - with the primary feature of interest being support for parallel programming, particularly arrays.

A simple ‘hello world’ Fortran 90 program looks as follows:

program hello
    ! This is a comment
    print *, 'Hello world'
end program hello

which can be compiled with:

gfortran hello.f90 -o hello