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"Consistently separating words by spaces became a general custom about the tenth century A.D., and lasted until about 1957, when FORTRAN abandoned the practice." —Sun FORTRAN Reference Manual

General

• If you comment out a piece of code, put a clear comment about the reason to do it. Otherwise is not clear why something is commented.
• Always use BLAS if a sentence is suitable. But don't use BLAS if a vectorial expression or a single loop has to be replaced by several blas calls.

Fortran

• Indentation: 2 blank spaces (not tabs) for all structures.
• Procedure dummy arguments (parameters) definition:
  • It must follow the declaration of the procedure (with no blank line in the middle).
  • One variable per line.
  • The intent and the :: in the declaration must be aligned.
  • It must follow the same order that in the declaration.
  • The intent must be always declared (all non-modified variables must be intent(in)).
  • A blank line must separate the declaration of local variables.
  • The upper bound of arrays and functions must not be declared, the lower bound only should be declared if it is not 1.
• About names:
  • Prefer long variable names.
  • Avoid one letter variable names (use ii instead of i).
  • Do not use the same name for different entities.
  • Lower case: variables, procedure names, module names, filenames.
  • Upper case: preprocessor macros and constants (parameters).
  • Module names must always end with _m.
  • Derived type names must always end with _t.
  • Files that are included must end with _inc.
• All Fortran keywords must be typed in lower case.
• All modules must be declared private and implicit none.
• Procedures belonging to a module do not need to be declared implicit none.
• The list of modules used must be in alphabetic order.
• Always give the explicit name for optional arguments.
• If it is possible and doesn't degrade performance, declare types as private and define access functions.
• Insert calls to push_sub() and pop_sub() at beginning and end of subroutines and functions (see Emacs helpers for some Elisp to do this automatically), except in functions that are critical for performance.
• Variables must be initialized to zero if required, do not rely on the compiler for this.
• Declare interfaces for all external functions.
• Do not use the ' character in comments, this confuses the C preprocessor.
• Do not declare variables as pointer unless is necessary.

C

• C code must be ansi compliant (ANSI ISO C90), among other things this means:
  • Variables must be defined at the begining of the block.
  • Only /* */ comments.
  • You can use the inline and restrict modifiers, autoconf handles this in case is not supported by the compiler.
• Declare non-modified arguments as const.

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