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How a Monitor Works

Raster Cathode Ray Tubes (CRTs)
most common display device
Electron beam scanned in regular pattern of horizontal scanlines.
Raster images
are stored in a frame buffer.
Frame buffers
are composed of VRAM (video RAM).
is dual-ported memory capable of
At each pixel in scanline, intensity of electron beam modified by the pixel value being shifted synchronously out of VRAM.

Colour CRTs
have three different colours of phosphor and three independent electron guns.
Shadow Masks
allow each gun to irradiate only one colour of phosphor.


Colour is specified either In the latter case, a colour index is stored in the frame buffer.

Reading: Hearn and Baker, Chapter 2. Red book, Chapter 4. White book, Chapter 4.

CS488/688: Introduction to Interactive Computer Graphics
University of Waterloo
Computer Graphics Lab