Width% = 200
      Height% = 200

      REM Set window size:
      VDU 23,22,Width%;Height%;8,16,16,128

      REM Draw circles:
      PROCcircle(100,100,40, 0,0,0)
      PROCcircle(100,100,80, 255,0,0)
      END

      DEF PROCcircle(cx%,cy%,r%,R%,G%,B%)
      LOCAL f%, x%, y%, ddx%, ddy%
      f% = 1 - r% : y% = r% : ddy% = - 2*r%
      PROCsetpixel(cx%, cy%+r%, R%,G%,B%)
      PROCsetpixel(cx%, cy%-r%, R%,G%,B%)
      PROCsetpixel(cx%+r%, cy%, R%,G%,B%)
      PROCsetpixel(cx%-r%, cy%, R%,G%,B%)
      WHILE x% < y%
        IF f% >= 0 THEN
          y% -= 1
          ddy% += 2
          f% += ddy%
        ENDIF
        x% += 1
        ddx% += 2
        f% += ddx% + 1
        PROCsetpixel(cx%+x%, cy%+y%, R%,G%,B%)
        PROCsetpixel(cx%-x%, cy%+y%, R%,G%,B%)
        PROCsetpixel(cx%+x%, cy%-y%, R%,G%,B%)
        PROCsetpixel(cx%-x%, cy%-y%, R%,G%,B%)
        PROCsetpixel(cx%+y%, cy%+x%, R%,G%,B%)
        PROCsetpixel(cx%-y%, cy%+x%, R%,G%,B%)
        PROCsetpixel(cx%+y%, cy%-x%, R%,G%,B%)
        PROCsetpixel(cx%-y%, cy%-x%, R%,G%,B%)
      ENDWHILE
      ENDPROC

      DEF PROCsetpixel(x%,y%,r%,g%,b%)
      COLOUR 1,r%,g%,b%
      GCOL 1
      LINE x%*2,y%*2,x%*2,y%*2
      ENDPROC