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A calculator watch is a digital watch with a built-in calculator, usually including buttons on the watch face. Calculator watches were first introduced in the 1970s and continue to be produced, despite falling from their peak popularity during the 1980s. The most dominant brands were the Casio Databank series and Timex.
Most calculator watches perform only basic arithmetic operations (addition, subtraction, multiplication, and division). However, there are several models with additional functions: scientific, including transcendent and trigonometry, in models Casio CFX-20, CFX-200, CFX-400 and Citizen 49–9421, financial functions (Casio CBA-10) and also TV remote control functions (CMD-40B and CMD-30B).
Usually, calculator watches operate with eight-digit numbers; however, calculator watches can work with six digits (for example, Casio C-801) or ten-digit (Casio CBA-10).
Another popular calculator watch was the Time Computer Calculator 901, which could perform basic arithmetic functions. The 902 models had additional functions such as percentage calculations. The Time watches carried a high price tag (US$4,000) because they were made of solid gold and operated by a stylus pen owing to the small size of their buttons.
Japanese electronics company Casio produced the widest variety of watches. In the mid-1980s, Casio created the Databank calculator watch, which performed calculator functions and stored appointments, names, addresses, and phone numbers. The calculator watches made by Casio earned much fame due to their appearance in movies and also due to being celebrities' choice during public events.
Mass-produced calculator watches appeared in the early 1980s, with the most being produced in the middle of the decade. Their popularity began to fade in the mid-1990s with the introduction of cheaper mobile phones and PDAs, which could perform the same functions. The calculator watch is now a collector's item, and notable watches such as the Timex watches and some special variants of Casio calculator watches such as the CFX-400 command a high premium in the used market.