Designed primarily as a computer for children, the Atari 400 has an "advanced child-proof design featuring pressure-sensitive, wipe-clean keyboard". It has a single cartridge port under the front cover.

The Atari 8-bit family is a series of 8-bit home computers introduced by Atari, Inc. in 1979 and manufactured until 1992. All of the machines in the family are technically similar and differ primarily in packaging.

Announced: December 1978
Released: November 1979
Price: US $549.95
CPU: MOS 6502,1.8MHz
RAM: 8K base, 48K max
Display: 24 X 40 text
320 x 192 monochrome
160 x 96 with 128 colors
Expansion: 2 internal expansion slots
1 cartridge slot under front cover
Ports: 4 controller ports
TV video output
Storage: external floppy drive
cassette recorder
OS: Atari OS

Source: http://oldcomputers.net/atari400.html

You could play arcade quality games on this gem too!

And of course, the greatest computer game of all time with four players. Programmed by one person!