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
Sumlock ANITA calculator £50,000 GBP but to be competitive with mechanical calculators the target selling price of the electronic calculator was in the range £350 to £400. The first all-electronic prototype was demonstrated to the board of the company in December 1958. This prototype was later donated by the company to the Science Museum in London, where Kitz had originally had the idea for the electronic calculator. It has been on display surrounded by the mechanical calculators that it was to make obsolete. There then followed several years of great effort in finding electronic and mechanical components suitable for production, testing them for