Help with drawing a shape in a window

Just for fun I am making a program to draw shapes in a window but not usin OpenGL or anything like that. Here is what I got so far. I know its crap :D you can only draw a 5 * 5 rectangle because I couldent figure out how to work with pointers. Any ways what I really want is to make the DrawRecta function to put pixels to fully cover the whole rectangle but I have no idea how to do that, any ideas? you might even have fun!

:D forgot the attachment...
Here it is

Polygon() is a function that will do that for you in one call.

edit: Never mind, I thought I was in the windows forum for a minute.

Basically you're looking for rasterizing of a polygon. For convex, that's easy. For concave, it'll require more thought. I've got an excellent concave polygon rasterizing algorithm that I wrote, but unfortunately it is the property of the company now ;)