Here are some hints for how to track them down. Useful compiler options Most Fortran compilers will have a set of options you can turn on if you like. One line per module with the size of the stack frame and code in bytes. Make sure your lines end at column 72. If you have a bug, you have to try to locate it.
Syntax errors are easy to find.
The problem is when you have run-time errors. The old-fashioned way to find errors is to add write statements in your code and try to track the values of your variables. This is a bit tedious since you have to recompile your source code every time you change the program slightly. You can step through a program line by line , you can display the values of the variables you want to monitor, and much more. When the program has been compiled with the -D option, a run time error will give an error message and wait for a command.