10 GRAPHICS 0
20 DLIST=PEEK(560)+256*PEEK(561)
30 LMSLOW=DLIST+4
40 LMSHIGH=DLIST+5
50 SCREENLOW=0
60 SCREENHIGH=0
70 SCREENLOW=SCREENLOW+40:REM Next line
80 IF SCREENLOW<256 THEN GOTO 120:REM Overflow?
90 SCREENLOW=SCREENLOW-256:REM Yes, adjust pointer
100 SCREENHIGH=SCREENHIGH+1
110 IF SCREENHIGH=256 THEN END 
120 POKE LMSLOW,SCREENLOW
130 POKE LMSHIGH,SCREENHIGH
140 GOTO 70