Hello world Fortran 90, 95, 2003, 2008, 2018

! Hello world program
! Languages:
!   - Fortran 90 (ISO/IEC 1539:1991)
!   - Fortran 95 (ISO/IEC 1539-1:1997)
!   - Fortran 2003 (ISO/IEC 1539-1:2004)
!   - Fortran 2008 (ISO/IEC 1539-1:2010)
!   - Fortran 2018 (ISO/IEC 1539-1:2018)

program HelloWorld
    print*, "Hello world!"
end program