Computer-aided design is essentially based on a versatile and powerful technique called computer graphics, which basically means the criterion and manipulation of pictures on a display device with the aid of a computer. Computer graphics originated at the Massachusetts institute of technology (MIT) in 1950when the first computer-driven display, linked to a Whirlwind 1 computer, and was used to generate some pictures. The first important step forward in computer graphics came in 1963 when a system called SKETCHPAD was demonstrated at the Lincoln Laboratory of MIT. This system consists of a cathode ray tube (CRT) driven by TX2 computer. The CRT had a keyboard and a light pen. Pictures could be drawn on the screen and then manipulated interactively by the user via the light pen.