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
Expensive Desk Calculator Expensive Desk Calculator Expensive Desk Calculator by Robert A. Wagner is thought to be computing's first interactive calculation program. The software first ran on the TX-0 computer loaned to the Massachusetts Institute of Technology (MIT) by Lincoln Laboratory. It was ported to the PDP-1 donated to MIT in 1961 by Digital Equipment Corporation. Friends from the MIT Tech Model Railroad Club, Wagner and a group of fellow students had access to these room-sized machines outside classes, signing up for time during off hours. Overseen by Jack Dennis, John McKenzie and faculty advisors, they were personal computer users as early as