Some frequently occurring errors

• The parameter list of a subroutine is incorrect. The number of parameters can be wrong, or parameters can be of the wrong type. The compiler messages are often unclear or are not given at all.
  Example: an integer (often 0 or 1) is given in the parameter list instead of a real or a double precision. Instead of 0 of 1 0d0 of 1d0 should be given.
• One goes out of the array index range. The error message is unclear or not given at all. Check array ranges very well yourself.
  Typical error messages are, for example:

     Segmentation fault - core dumped
     Bus error
  

• Division of 2 integers is not rounded but truncated (1/2 = 0)
• variables are treated as being different while they are the same. As explained above, FORTRAN is case-insensitive. For instance, tnew, Tnew, TNEW and tNEW are considered exactly the same in FORTRAN.

System error messages are also not always very clear.
Often occurring error messages are:

  Floating point exception
  Underflow
  Bus error
  Memory fault
  Segmentation violation

The last three error messages really only tell you that something is terribly wrong, but not exactly what and where.
The first message occurs often when a division by 0 is performed. Check where you perform divisions.
The message underflow often indicates that something has no value but is still being used.
Sometimes some extra information is given about the position where the error occurs. This helps you finding the error.
When looking for errors in a program, include print statements in your FORTRAN program to check what is going on.
If very many error messages occur on the screen, use redirection to a file. For system messages, use >&.