The smaller Atari 400 and this are introduced in December 1978 and first sold in 1979. The machines are based on the MOS 6502 CPU and are very important in the history of computers.

Before their release, home computers were not great with gaming. It was possible, but the hardware was very limited. Game consoles, like the Atari 2600, had specialized chips for sound and video.
The person who led this division of Atari was Jay Miner, the same person who created the Commodore Amiga 1000 a few years later. Jay developed chips which supported hardware sprites and collision detection, removing these functions from the CPU and therefor having more CPU power left to create a better game. With this, both Atari 400 and 800 were the ultimate game machines in the late 1970s. This also meant both Atari's were the first to combine a game console and a home computer.

The Atari 800 is aimed for both office work and gaming. The very nice keyboard and 4 connections for joysticks underline this. In total up to 4 disk drives can be connected (Atari 810) which can transfer data up to 19200 bps. Every disk can hold 90 KB. Despite all this, the cassette recorder is used more for storage because it was cheaper.

There's room for 2 cartridges in the machine, labelled left and right. Most cartridges are 'lefties' which is also stated on the cartridge itself. There were many expansions for this Atari. A printer (Atari 820), modem (Atari 830 coupler or Atari 835 as real modem) or interface module (Atari 850) are a few examples. Below the hood on the front (behind the cartridges) there are 4 expansion busses for adding memory.