Released from 1980 until 1982. The Atom was a home computer from Acorn. It was essentially a progression of the MOS-6502 based machines that the company had been producing from 1979.
The Atom was Acorn’s first computer to be aimed directly at the home computer market. In 1982 it was replaced by the BBC Micro, which initially started life as an upgrade to the Atom, which was originally known as the Proton.