Calculator watch financial functions (in the Casio CBA-10). Usually calculator watch operates with eight digits number, however, calculator watch can operate with 6 digits (for example, Casio C-801) or 10 digits (Casio CBA-10) numbers. Calculator watches first appeared in the mid 1970s introduced by Pulsar (1975, then a brand of the Hamilton Watch Company) and Hewlett Packard. Several watch manufacturers have made calculator watches over the years, such as Pulsar and Timex, but the Japanese electronics company Casio produced the largest variety of models. In the mid-1980s, Casio created the Databank calculator watch, which not only performed calculator functions, but also stored
Calculator four AA-size cells the LE-120A measures . The first European-made pocket-sized calculator, DB 800 is made in May 1971 by Digitron in Buje, Croatia (former Yugoslavia) with four functions and an eight-digit display and special characters for a negative number and a warning that the calculation has too many digits to display. The first American-made pocket-sized calculator, the Bowmar 901B (popularly termed "The Bowmar Brain"), measuring , came out in the Autumn of 1971, with four functions and an eight-digit red LED display, for $240, while in August 1972 the four-function Sinclair Executive became the first slimline pocket calculator measuring