Make sure the file name you entered in the dialog box
conforms to these rules and assumptions used by QuickBASIC:
  ■ A file name has two parts: the "base name", which is
    everything up to but not including the period (.), and
    the "extension," which includes the period and up to
    three characters. You can use any combination of upper-
    and lower-case characters; these example filenames all
    refer to the same file:
      abcde.bas, ABCDE.BAS, and aBcDe.BaS
  ■ If the file name is 8 or less characters with no
    period, QuickBASIC assumes the extension .BAS. If the
    file name is between 9 and 11 characters, QuickBASIC
    puts a period after the eighth character.