Fortranstyle

Fortranstyle is a term used to describe a coherent set of coding conventions and practices intended for Fortran software development. It emphasizes readability, portability, and maintainability across Fortran dialects (Fortran 90/95, 2003, 2008, and later) and compiler implementations. While not an official standard, it is adopted by groups and projects to ensure consistent codebases.

Core principles include explicit typing using implicit none; modular design with programs, modules, and procedures; descriptive identifiers and consistent naming schemes; and documentation via inline comments using the “!” character and, where appropriate, external documentation. Code should minimize global state and avoid nonlocal side effects; prefer explicit interfaces for procedures, using modules and interface blocks rather than implicit interfaces. Use of modern Fortran features such as array operations, elemental and pure procedures, and modules for data encapsulation is encouraged.

Formatting and layout practices typically cover indentation (commonly 2–4 spaces), consistent line breaks, and clear continuation rules in free-form source (using “&” to join lines, avoiding hard-wrap in the middle of logical statements). Local variable scope should be clear, with explicit intents for dummy arguments (intent(in), intent(out), intent(inout)).

Adoption varies by project but is common in scientific and high-performance computing where large legacy codebases migrate to modern Fortran. The aim is to improve portability, error detection, and long-term maintainability, while preserving the expressive power of the language.