Casio 121
Image Courtesy of Mr. Serge Devidts, Calcuseum

The Casio 121, along with stablemates Casio 120 and 161, were Casio's first foray into electronic calculators utilizing first-generation Japanese-made MOS (Metal-Oxide Semiconductor) integrated circuits. Previous Casio desktop calculators were constructed using discrete transistor circuitry. The 121 has twelve digits of capacity, a single accumulating memory register, and offers fixed or floating decimal. It has a round-off mode, and supports negative numbers. The display is composed of individual Hitachi-made Nixie tube display elements. Circuitry is contained on four plug-in circuit boards, populated with small-and medium-scale IC's in both metal can-type and DIP (Dual Inline Package) packages. Register storage is by dynamic shift registers. This series of calculators was introduced sometime in 1968, and was sold until the early 1970's. This machine was also marketed in North America by Canadian electronics distributor Commodore, as the Commodore 1121.