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documentation, particularly for programming, you should not rely on the information found here, as it will be woefully out of date.
Invalid identifier
You have used a character that is not valid in an
identifier. Make sure that:
  ■ DEF FN procedure names contain only letters and
    numbers.
  ■ FUNCTION and SUB procedure names start with a
    letter and do not contain these special characters:
    ., %, &, !, #, or $.