question about coordinate system

OpenGL OpenGL: Basic Coding
1

I havent read much yet, but would like to know if the foll is possible. I want to set my coord system so that it goes from -180 to 180, and -90 to 90. Then I draw some lines in it. After that I want my coord system to go from 0-100, 0-50, and I draw some sqaures in that, so that I see all lines and sqaures I drew (even though they are scaled differently). If this is not possible I wont use openGL. If it is, what commands do I look at? I know how to draw the lines etc, but none of the simple stuff I’ve looked at shows me how to change my scale midway. Appreciate the help,
sb

2

You use glOrtho for that. That will set the coordinate system to whatever range you want.

3

Thanks much for your helpful response.
Sb