I am not sure but I don't think there is any limit what so ever. I just ran this code

code:
redirectoutput("d:\kixgolf\kixstr.txt",1)
dim $i, $e, $str
$i=1
$str='x'
DO
  $i=4*$i
  $str=$str+$str+$str+$str
  $e=@error
  ? $i
UNTIL $e<>0 or len($str)<>$i
 ? ' *** stopped *** ' $i
and it seemed to effectively stop at$i=67,108,864. At this point I was using amost all my physical memmory & almost all my virtual memory & nothing was happening. When I tried opening other apps to see if I could find out what was happening the system became unstable & started shutting down apps & trying to reboot. at this point my best guess is it corrupted the virtual memory file because I keep getting a disk check error on reboot. Fortunately, my machine is dual boot & I was able to do a diskcheck from the 2nd version & rectify the problem.
_________________________
Jack