NCR 18  
Written by Accutron on 2016-05-25  

The NCR 18 is a rebranded version of the NCM/Busicom 162, a fairly early 16-digit electronic desktop calculator introduced in 1967. Although Busicom was a relatively short-lived Japanese company, their technology needs had a profound impact on the US microprocessor industry. Busicom worked with Mostek to develop the first single-chip calculator (MK6010), and commissioned Intel to develop the 4004, the first commercially available general purpose microprocessor. The Busicom 162 and its NCR siblings predate these efforts.

The NCR 18 is built with Signetics ST600 series discrete DTL, a Nixie tube display and Mitsubishi core memory to store register values. Internal construction consists of a dense card cage and backplane. The core memory array is arranged as a single 16x16 plane, for a total of 256 bits. The NCR 18 has two independent accumulating registers, with individual clear, recall, add and subtract keys. Another unusual 'feature' of the NCR 18 is that its core memory contents are actively erased when the calculator is turned off.

There appears to be some ambiguity regarding the different variants of the NCR 18. The Old Calculator Web Museum has a model 18-2 in their collection with no square root function, and Calcuseum has a model 18-3 with square root function, which appears to be functionally identical to the 18-2 in our collection. The official brochure for the NCR 18 features a calculator both functionally and cosmetically identical to the unit pictured here, and delineates no model subtypes. Known machines held in other collections are cosmetically slightly different than the calculator pictured in the brochure.

Early Busicom calculators are very rare. Only a handful of NCR 18 and Busicom 162 machines are known to still exist, and the example pictured here is currently the only extant specimen of the exact variant shown in the NCR 18 brochure. The NCR 18 is also the oldest electronic computing machine in our collection.

NCR 18 Brochure (PDF)
Busicom 162 Brochure (PDF)

NCR 18 electronic calculator.

NCR 18, card cage and display assembly.

NCR 18, logic and memory cards.

NCR 18, enlargement of Mitsubishi magnetic core memory.

NCR 18, rear placard.

This article is part of the [Electronic Calculators] exhibit.

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