static char mask[] = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
static int addr[] = { 0x000, 0x060, 0x060*2, 0x060*3, 0x060*4, 0x060*5, 0x060*6, 0x060*7, };

static char number_font[] = {
    0x3e, 0x41, 0x41, 0x41, 0x3e, 0x00, /*0*/
    0x00, 0x42, 0x7f, 0x40, 0x00, 0x00, /*1*/
    0x42, 0x61, 0x51, 0x49, 0x46, 0x00, /*2*/
    0x22, 0x41, 0x49, 0x49, 0x36, 0x00, /*3*/
    0x1c, 0x13, 0x10, 0x7f, 0x10, 0x00, /*4*/
    0x2f, 0x49, 0x49, 0x49, 0x31, 0x00, /*5*/
    0x3e, 0x49, 0x49, 0x49, 0x32, 0x00, /*6*/
    0x01, 0x01, 0x71, 0x09, 0x07, 0x00, /*7*/
    0x36, 0x49, 0x49, 0x49, 0x36, 0x00, /*8*/
    0x26, 0x49, 0x49, 0x49, 0x3e, 0x00, /*9*/
    0x7c, 0x12, 0x11, 0x12, 0x7c, 0x00, /*A*/
    0x7f, 0x49, 0x49, 0x49, 0x36, 0x00, /*B*/
    0x3e, 0x41, 0x41, 0x41, 0x22, 0x00, /*C*/
    0x7f, 0x41, 0x41, 0x41, 0x3e, 0x00, /*D*/
    0x7f, 0x49, 0x49, 0x49, 0x49, 0x00, /*E*/
    0x7f, 0x09, 0x09, 0x09, 0x09, 0x00, /*F*/
    0x08, 0x08, 0x08, 0x08, 0x08, 0x00, /*-*/
};

static int font_offset[] = { 0, 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96 };

void print_digit(int x, int y, int digit)
{
    char *ad = (char *)0x1000 + addr[y] + x;
    char *font_pos = number_font + font_offset[digit];
    char i;
    for(i=0; i<6; i++)
        ad[i] = font_pos[i];
}

int digits[] = { 0, 1, 10, 100, 1000, 10000 };
void print_dec(char x, char y, int num)
{
    if(num < 0)
    {
        print_digit(x, y, 16); /* - */
        print_dec(x + 6, y, -num);
        return;
    }
    else
    {
        char i, j;
        for(i=5; i>1; i--)
            if(digits[i] <= num)
                break;
        for(; i>0; i--)
        {
            for(j=0; j<10; j++)
            {
                if(num < digits[i])
                    break;
                num -= digits[i];
            }
            print_digit(x, y, j);
            x += 6;
        }
    }
}

void print_hex(char x, char y, unsigned num)
{
    char i;
    for(i=12; i>=0; i-=4, x+=6)
        print_digit(x, y, (num >>i) & 0x0f);
}

void print_bin(char x, char y, unsigned num)
{
    char i;
    for(i=15; i>=0; i--, x+=6)
        print_digit(x, y, (num >>i) & 0x01);
}

void draw_pixel(char x, char y)
{
    char m = mask[y & 0x07];
    *(char *)(0x1000 + addr[y >> 3] + x) |=  m;
}

void draw_circle(char xc, char yc, char r)
{
    unsigned int x= r, y= 0;
    int          cd2= 0;

    if (!r) return;
    draw_pixel(xc-r, yc);
    draw_pixel(xc+r, yc);
    draw_pixel(xc, yc-r);
    draw_pixel(xc, yc+r);

    while (x > y)
    {
        cd2-= (--x) - (++y);
        if (cd2 < 0) cd2+=x++;

        draw_pixel(xc-x, yc-y);
        draw_pixel(xc-y, yc-x);
        draw_pixel(xc+y, yc-x);
        draw_pixel(xc+x, yc-y);
        draw_pixel(xc-x, yc+y);
        draw_pixel(xc-y, yc+x);
        draw_pixel(xc+y, yc+x);
        draw_pixel(xc+x, yc+y);
     }
}

int main()
{
    char a, i;

    for(i=0; i<=0xe; i++)
        print_digit(3 + font_offset[i], 6, i);

    for(a = 0; a <80; a++)
        draw_pixel(a+10, 5 +(a>>1));
    draw_circle(25, 20, 15);
    draw_circle(35, 25, 21);
    draw_circle(63, 30, 29);
    draw_circle(63, 30, 26);

    for(;;)
        ;
    return 0;
}