This is probably a very simple question, but the answer is surprisingly hard to find. I have a CRT monitor with a dot pitch of 0.22mm x 0.14mm x 0.26mm (Hor. x Vert. x Diagonal), and a max resolution of 1600x1200 (this is a 4:3 display). The viewable area is 18" which translates to roughly these values in millimeters: Viewable: 457.2 mm Horizontal: 345.44 mm Vertical: 299.72 mm Dividing the horizontal dimension by the horizontal pitch, I get 1570 pixels. Since the max resolution is 1600 I assume that the remaining 30 pixels are missing due to some rounding noise in my calculations. Anyways, this isn't my issue. Assuming there are 1600 pixels, using a resolution of 800x600 or 400x300 would constitute a doubling and quadrupling of horizontal pixels into a group respectively, but what about a resolution such as 1024x768? How does a CRT group its pixels in such a way as to allow these "in between" resolutions?