pixel

Computer screen images are made of a number of pixels (‘dots’). The greater the number of pixels the greater the resolution of the image; most computer screens are set at 640 × 480 pixels, although higher resolutions are available.

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). The number of pixels available determines the screen's resolution. Typical resolutions of microcomputer screens vary from 640 × 480 pixels to 1,024 × 768 pixels, but screens with 1,600 × 1,200 pixels or more are now common for high-quality graphic (pictorial) displays.

The number of bits (binary digits) used to represent each pixel determines how many colours it can display: a two-bit pixel can have four colours; an eight-bit (one-byte) pixel can have 256 colours. The higher the resolution of a screen and the more colours it is capable of displaying, the more memory will be needed in order to store that screen's contents.