qbasic.hlp (Topic list)
Important Notice
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documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.
DEF FN not allowed in control statements
DEF FN function definitions are not permitted inside control
statements such as IF...THEN...ELSE and SELECT CASE.