The Atom was a cut-down Acorn System 3 without a disk drive but with an integral keyboard and cassette tape interface, sold in either kit or complete form.

In 1980 it was priced between £120 in kit form, £170 (equivalent to £921 in 2023) ready assembled, to over £200 for the fully expanded version with 12 KB of RAM and the floating-point extension ROM.

It had a built-in minor variation of Acorn System BASIC, a fast but idiosyncratic version of the BASIC programming language developed by Sophie Wilson, which included indirection operators (similar to PEEK and POKE) for bytes and words (of 4 bytes each); the use of a semi-colon to separate statements on the same line of code (instead of the colon used by most if not all other versions of BASIC); and the option of labels rather than line numbers for GOTO and GOSUB commands.

[5] The Acorn 8V power supply was only rated to 1.5 amps, which was not enough for an Atom with fully populated RAM sockets.

The Atom was incorporated into a "complete dedicated spreadsheet system" known as the Prophet by a company called Busicomputers, with the second edition of this product, the Prophet 2,[6] consisting of a modified Atom, Ferguson 12-inch black-and-white television, and a Pearlcorder microcassette recorder, all housed in a "robust metal case".

Powered by a single mains plug, the system was effectively a "turnkey" solution, emphasising the built-in spreadsheet as its primary function.

Although regarded as worth considering as an "inexpensive way of obtaining a sound and reasonably well-presented spreadsheet system", being priced at £795 plus VAT, the use of cassette storage to reduce the system's cost was regarded as impacting its usability, with the slow data transfer rate causing waits of 30 minutes or more to save spreadsheet data and limiting the effective storage capacity of the microcassettes, whereas more expensive disk-based systems would be able to transfer similar volumes of data in a matter of seconds and store tens of spreadsheets on each disk.

[7] Regarded as "low-tech" later in 1983, the Prophet II was apparently being given away to participants of one- or two-day business-related training courses, these costing £600 and £700 respectively, with this initiative considered "a nice way of moving old stock".