BASIC: What does an exclamation mark at the end of a function name mean?

Question

DECLARE FUNCTION AanUit! (Baan AS INTEGER, Aktie AS INTEGER)
DECLARE FUNCTION fVraagStatus! (Baan AS INTEGER)
DECLARE FUNCTION fMelding! (Tekst AS STRING, Warning AS INTEGER)

FUNCTION fVraagStatus (VraagBaan AS INTEGER)
  ´ retrieve status somewhere
  fVraagStatus = False or True
END FUNCTION

FUNCTION fMelding (Tekst AS STRING, Warning AS INTEGER)
  ´ locate (move cursor), print stuff
END FUNCTION

My Question: What does an exclamation mark at the end of a function name mean?

I am rewritting an old program to .net and came across something weird and i want to understand why there is a '!' at the end of the function decleration. I don't really need to write my own code, it's Just for my peace of mind.

Answer 1

It means the function returns a SINGLE. Exclamation point is a shortcut for As Single.