Calc Crash (Real and Virtual)

[toml_12953]

When I run the following program to compute the Ackermann function, both the virtual and real calculators crash. I expected to get an error but not a crash.
Try running it for X=4 and Y=3

Tom L

Code:

FNA(M,N)
BEGIN
  IF M==0 THEN
    RETURN N+1;
  END;
  IF N==0 THEN
    RETURN FNA(M-1,1);
  ELSE
    RETURN FNA(M-1,FNA(M,N-1));
  END;
END;

EXPORT ACKERMANN()
BEGIN
  WHILE 1==1 DO
    PRINT();
    INPUT({X,Y},{'X','Y'});
    MSGBOX("Ackermann= "+FNA(X,Y));
    GETKEY;
  END;
END;