Programmable calculator to use magnetic strips were the HP-41C and TI-59. Continuous memory does not lose its content when the calculator is switched off. With continuous memory the user can, for example, change batteries without losing the entered programs. Compact Cassettes offered a simple, inexpensive alternative to magnetic cards. Usually, an interface module, such as the Casio FA-1, was used to connect the calculator to an ordinary cassette recorder and digital data were encoded as frequency-shift keyed audio signals. Sharp and Hewlett-Packard also sold dedicated micro- or mini-cassette recorders that connected directly to the calculator. These set-ups, while being more practical and
The Millionaire Calculator The Millionaire Calculator The Millionaire calculator was the first commercially successful mechanical calculator that could perform a direct multiplication. It was in production from 1893 to 1935 with a total of about five thousand machines manufactured. The principle of a calculation machine with progressive transmission of tens was invented by Chebyshev and demonstrated at the 1878 World's fair in Paris. In 1881 Chebyshev demonstrated a model of the calculation machine with automatic multiplication but did not take out a patent for it. In 1834 Luigi Torchi of Milan invented a direct multiplication machine. The first patented multiplying machines was due