{

for (int y=0; y<YMAX; y++)

for (int x=0; x<XMAX; x++)

screen[x][y] = white;

{

register int dx = 1;

int a = x1 - x0;

if (a < 0) dx = -1, a = -a;

register int dy = 1;

int b = y1 - y0;

if (b < 0) dy = -1, b = -b;

int two_a = 2*a;

int two_b = 2*b;

int xcrit = -b + two_a;

register int eps = 0;

for(;;) {

put_point(x0,y0);

if (x0==x1 && y0 == y1) break;

if (eps <= xcrit) x0 += dx, eps += two_b;

if (eps>=a || a<=b) y0 += dy, eps -= two_a;

}

{

for (int y=YMAX-1; 0<=y; y--) { // top to bottom

for (int x=0; x<XMAX; x++) // left to right

cout << screen[x][y];

cout << '\n';

}