OpenGL 2D Origin in Upper Left Corner

Question

I got an OpenGL Context Working in SDL, and I'm trying to set it up so I can render with pixel coordinates of the screen. I got this trying to fill the entire screen with a white rectangle:

glViewport(0, 0, MonitorWidth, MonitorHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, MonitorWidth, MonitorHeight, 0, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glClearColor(0, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glColor3f(1, 1, 1);

glBegin(GL_QUADS);

glVertex2f(0, 0);
glVertex2f(MonitorWidth, 0);
glVertex2f(MonitorWidth, MonitorHeight);
glVertex2f(0, MonitorHeight);

glEnd();

It doesn't work, and the entire screen appears black. What's wrong with this?

Answer 1

Aright I fixed it:

glViewport(0, 0, MonitorWidth, MonitorHeight);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho(0, MonitorWidth, MonitorHeight, 0, -1, 1);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();

glClearColor(1, 0, 0, 1);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

glColor3f(1, 1, 1);

glBegin(GL_QUADS);

glVertex2i(0, 0);
glVertex2i(MonitorWidth, 0);
glVertex2i(MonitorWidth, MonitorHeight);
glVertex2i(0, MonitorHeight);

glEnd();