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
Sharp QT-8D Sharp QT-8D The Sharp QT-8D Micro Compet, a small electronic desktop calculator, was the first mass-produced calculator to have its logic circuitry entirely implemented with LSI ("large-scale integration") integrated circuits (ICs) based on MOS ("metal-oxide-semiconductor") technology. When it was introduced in late 1969, it was one of the smallest electronic calculators ever produced commercially. Previous electronic calculators had been about the size of a typewriter and had logic circuits built from numerous discrete transistors and diodes or small- to medium-scale ICs. The QT-8D's logic circuits were packed into just four LSI ICs. The QT-8D was released in Japan at a