Using f77-c to do separate compilations

To separately compile Fortran modules before linking them together, use the '-c' option to the 'f77' compiler. For example, if you have two source files, named 'file1.f' and 'file2.f', type these commands:

        f77 -c file1.f
        f77 -c file2.f

You now have 2 object code files named file1.o and file2.o.
Now you can link them together with this command:

        f77 file1.o file2.o

You can use this strategy to save time as you develop your code. You only need to recompile those Fortran modules that have been changed since it was last compiled. Once you have recompiled any changed modules, you can link them together as shown above. As your modules get larger, doing this can save you quite a bit of time.

If you have many modules in your program, you may want to consider using 'make' which automatically figures out which of your modules need to be recompiled (by checking when they were last modified), and then links them.

If you want to learn more about 'f77' or 'make', you can read the manual pages by using the 'man' command:

        man f77

or

        man make

NOTE: On the RS/6000 workstations the name of the Fortran compiler is "xlf", and not "f77".