Microsoft decided to change the order of function arguments of
the rename() function. Check the source against the documentation
of your compiler.

Some functions are used in all programs. Therefore, everything has to 
be compiled with the same memory model.

Since the assembly-language serial port driver assumes a small
memory model, all programs have to be compiled with the small memory
model.

The MAILDIR, EDITOR environment variables should hold absolute path
names. On MS-DOS systems (floppies!) it is a good idea to include
the drive name as well.

On some MS-DOS systems the directory listing (file command) does
not show the ".." entry.
