Programming
FEAP is designed to allow users to modify the code for their owm purposes. If at all possible, users should always use the user hooks provided in the user directory. These allow users to make custom elements, material models, new FEAP commands, et cetera. The programmers manual provides an introduction to programming in FEAP.
To use the user hooks, it is recommended to make a copy of the relevant stub file in a separate project directory. Then add the full path name to this edited copy to main/makefile on the OBJECTS line so that it will be built into FEAP the next time you compile it. If you are using windows, add the copy to your executable project. Even though there is a version of the stub file in your FEAP archive file, the compiler should use your edited copy instead of the one in the archive.
Programmers Manual
The programmers manual can be found on the FEAP project site http://projects.ce.berkeley.edu/feap.