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NCR 18-15 Desktop Calculator

Image Courtesy Ian Ormerod

The NCR 18-15, designed and manufactured by Nippon Calculating Machine Co.(NCM) (also known as Busicom) and licensed to NCR for sale under the NCR brand name. The 18-15 was the first easily portable desktop AC-powered calculator marketed by NCR. The unique design of the machine managed to cram the calculating brains onto three circuit boards containining only 22 integrated circuits. This was due to higher levels of integration (Medium-Scale integrated circuit devices), and clever packaging. The 18-15 was a 12-digit, vacuum-fluorescent display calculator, with fixed decimal point settings (slide switch), and the basic four math functions. The architecture of the 18-15 served as the design basis for a single-chip calculator IC made by MOSTEK (the first ever successful calculator-on-a-chip), which resulted in the follow-on to the 18-15, the NCR 18-16, a machine virtually identical functionally and visually, but was about 1/2-inch thinner, and slightly slower than the 18-15 due to the use of the early MOS (Metal Oxide Semiconductor) LSI (Large-Scale Integration) calculator chip.