Atari under the management of Ray Kassar (AKA the Czar by Atari employees) decided on the introduction of the Atari Home Computer Division. They made the Atari 400 and 800 the 400 being the entry level cheaper computer, had membrane  (like the ones you would find on a calculator) keys so that a young child would not spill his drink onto the keys and gum them up. Membrane keys are somewhat hard to do actual typing and starts to hurt your hands with prolong use. (BTW this is the opinion of the Atari Computer Database) The Atari 400 computer was the first computer that used, Player missile graphics later and more popularly known as Sprites. It was also the first computer to use a custom co-processor. This computer was far ahead of its time and used video interruptions such as display lists which would take years for other companies to use this even on the Commodore Amiga!  It started production in 1979 and was ended in 1982 as newer Atari computers had by far outdated this and its sister computer the 800.