In this Appendix we show the directory tree structure as you should find it under NEMO. Directory names preceded with a (*) are being fully exported by the export procedures. The ``src'' tree contains all of the official source code, and is expanded a bit on following pages. The ``usr'' (or ``contrib'') tree is what used to be the $NEMO/src tree in the first releases of NEMO (Version 1.x). Some of the code in $NEMO/usr is now outdated, and superseded by more recent versions somewhere in $NEMO/src tree. Any 'personal' (most public domain also) code should now be placed in the appropriate $NEMO/usr tree before it can be accepted (moved over) into the $NEMO/src tree. We advice programmers to stick as closely as possible to the install procedures in the $NEMO/src tree, if at all possible. See the Makefiles and the discussion on these in the Programmers Guide (see ).