Question

We have a complex program written in Fortran 90, I’ve only been able to find Fortran 95 compilers. Unfortunately I have limited access and experience but need immediate insight on the problem.

Will Fortran 90 code always compile correctly with a Fortran 95 compiler such as gfortran?

Answer 1

Fortran versions are backwards compatible, perhaps to a fault. In the Fortran95 standard, there were some very (deservedly) obscure constructs that were finally deleted: eg, from this page:

Fortran 95 indicates that the following Fortran 90 and FORTRAN 77 features have been deleted:

• ASSIGN and assigned GO TO statements
• PAUSE statement
• O control variables and expressions of type real
• H edit descriptor
• Branching to an END IF statement from outside the IF block

But unless your code uses those (and it shouldn’t), you should be fine with F95; and otherwise, most F95 compilers will still have a mode with which you could compile that older code, eg -std=legacy for gfortran.