Fortran is a very old programming language, you could say it's the oldest. Fortran, or FORTRAN, as it was originally written, was developed by IBM in the 1950s to be the first high level programming language. Rather than writing programs in assembler language, which is More suitable for reading by machines than by humans, FORTRAN was readable by people.
To compile and run the code in Linux machine :
Fortran program (.f90) => Compile (gfortran compiler) => Object file (.o) => Link => Executable program
$ gfortran hello_world.f90 -o hello_world
$ ./hello_world