Computer image formation. A small part of a computer screen showing the degree of resolution (detail) possible. Curved lines are not smooth but formed by the edges of many tiny square pixels. A pixel (contraction of 'picture element') is a single dot on a computer screen. All screen images are made up of a collection of pixels with each pixel being either off (dark) or on (illuminated, possibly in colour as in this image). The number of pixels available determines the screen's resolution. Typical resolutions of microcomputer screens vary from 320 x 200 pixels to 800 x 600 pixels, but screens with much greater resolutions are now common for graphic display.