DIM A

CLS
FOR A = 1 TO 1000
  IF IsPrime(A) THEN ?  A;
NEXT A

FUNCTION IsPrime (Num!)
  LOCAL X!
  IF MOD(Num!, 2) = 0 THEN
    EXIT FUNCTION
  END IF
  FOR X! = 3 TO Num! - 1 STEP 2
    IF MOD(Num!, X!) = 0 THEN
      EXIT FUNCTION
    END IF
  NEXT X!
  FUNCTION = -1 ' Return true if it's a prime number 
END FUNCTION

Result:

 Result not displayed for this example.