proc scrollcolors()

  BYTE wsync=54282, ;the 'wait for sync' flag
       vcount=54283,;scanline count flag
       clr=53272,   ;bkgrd register
       ctr,chgclr=[0],     
       incclr       ;incr luminance

  graphics(0)
  pute()
  for ctr=1 to 23
    do
      printe("A Demo of Shifting Background Colours")
    od
  print("A Demo of Shifting Background Colours")
  do
    for ctr=1 to 4
      do
        incclr=chgclr
        do
          wsync=0
          clr=incclr
          incclr==+1
        until vcount&128
      od
    od 
    chgclr==+1
  od
return