The pages on this site contain documentation for very old MS-DOS software,
purely for historical purposes.
If you're looking for up-to-date documentation, particularly for programming,
you should not rely on the information found here, as it will be woefully
out of date.
QBasic function not defined
The function defined by DEF FN does not exist, which
can indicate one of the following conditions:
■ The DEF FN function is undefined.
■ The DEF FN function is attempting to call itself
recursively.