#define PAGE1 ((char *)0x2000)
static int ysum, xoff, bitoff, point, point1;

static int
whpnt()
{
    if (bitoff!=6){
        point=3<<bitoff;
        point1=0;
    } else if (xoff != 39){
        point=0x40;
        point1=1;
    } else {
        point = 0x60;
        point1=0;
    }
}

static int
pnt(evencol,bit7)
register int evencol, bit7;
{
    int base;

    if (evencol)
        base=(xoff&1?2:1);
    else
        base=(xoff&1?1:2);

    point=bit7|base<<(bitoff&6);
    point1=0;

    if (bitoff==6)
        if (evencol)
            if (xoff&1) /*point 6 in odd bytes */
                point = bit7|0x20;
            else  /* point 6 in even bytes */
                point1=bit7;
        else
            if (xoff&1) {
                if (xoff != 0x27) /* if last point on line is red, don't */
                    point1=bit7;   /* turn on bit 7 of next byte */
            } else
                point = bit7|0x20;
}

static int
complot(x,y,func, evencol,bit7)
register int x,y;
int (*func)(), evencol,bit7;
{
    int y1,y2,y3;

    if(y<64)
        y1=0;
    else if (y<128)
        y1=0x28;
    else
        y1=0x50;
    y2=(y&7)<<10;
    y3=(y&0x38)<<4;
    ysum=y1+y2+y3;

    xoff=x/7;
    bitoff=x%7;

    (*func)(evencol, bit7); /*compute point & point1 */

#ifdef DEBUG
    printf("\n\ty1=%x, y2=%x, y3=%x\n",y1,y2,y3);
    printf("\txoff=%x,point=%x, point1=%x\n",xoff,point,point1);
#endif
    PAGE1[ysum+xoff] |= point;
    PAGE1[ysum+xoff+1] |= point1;
}

#define EVENCOL 1
#define ODDCOL 0

bplot(x,y)
{
    complot(x,y,pnt, EVENCOL, 0x80);
}

vplot(x,y)
{
    complot(x,y,pnt, EVENCOL, 0);
}

rplot(x,y)
{
    complot(x,y,pnt, ODDCOL, 0x80);
}

gplot(x,y)
{
    complot(x,y,pnt, ODDCOL, 0);
}

plot(x,y)
{
    complot(x,y,whpnt);
}