Fortran maximum name and line lengths

October 16, 2022

Ancient Fortran code readability is impacted by the restrictions on variable length and line length that could lead to inscrutable variable and procedure names. The Fortran 2003 standard raised many of these limits to lengths that might only be a factor for auto-generated code with internally used very long names. If going beyond the usual name lengths, it’s a good idea to test across the compilers of interest (including compiler versions) to ensure that the required compiler vendors and versions can support the proposed name lengths.

We provide code examples verifying that compilers can support 63 character syntax elements (names for modules, submodules, variables), which is the maximum set by Fortran 2003 standard. The maximum line length is officially 132, but can be much longer depending on the compiler and compiler options.