Good programming practice

1. Always use
   implicit none
   
2. Mark each subroutine clearly.
   Start each subroutine with a short description what is none, what input is neede and what output is given.
   Also write who has written the subroutine and when.
   
3. Divide your subroutins into a number of short and well-defined tasks (~10 program lines). Start each task with a short (~1 line) comment of what is done.
   Divide the tasks by a single empty line
   
4. Indent your file (emacs does that automatically).
5. Keep the 72 character lines.
6. Do not use continue but enddo
7. Let array dimensions always be named parameters, not explicit numbers (except for the three Cartesian dimensions).
8. Let file numbers be named variables, not explicit numbers.
   
9. Always use read*8 (=double precision)
10. Never use write(*,*) - it does not work in parallel; use write(6,*) instead.
11. Use long and instructive names for all variables (except do-loop indeces).
12. Always initialise all variables (even with 0).
13. Always remember to give .0d0 for all real constants (including 0.0d0, 1.0d0 and 2.0d0)
14. Make all scripts as general as possible: Assume that the programs are in your PATH and do not include an explicite path.
15. Always rename old versions of programs, not the new ones (the current preferred version should always have the simplest and most obvious name).
    

Sample file

Utility subroutines