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
Digital Compact Cassette and Compact Disc) while Philips decided on a tape format that was compatible with their earlier analog Compact Cassette format. DCC, initially referred to as S-DAT (stationary-head digital audio tape, as opposed to R-DAT—rotary-head digital audio tape), was developed in cooperation with Matsushita, and the first DCC recorders, were introduced at the CES in Chicago in May, 1992 and the consumer electronics show in Amsterdam in September 1992. At that time, not only Philips and Technics (brand of Matsushita) announced DCC recorders but also other brands such as Grundig and Marantz (both related to Philips at the time). More recorders