Apologies to those readers who, having read that 'all programs run in 16K' could not get DEM021 to run. The program itself uses just under 13K but of course this does not leave enough room for the Graphics 8 display. The answer is to split the program in two with lines 5000
and 32000 to 32020 in each and a GOSUB 32000 at the beginning. Sorry about that!