Magnetic cards

The magnetic card is a storage medium of the early calculators, introduced by Hewlett Packard HP -65 ( 1974), and the HP -67 and HP -97 (from 1975 ), and the HP -41C used ( from 1979). Later extended magnetic cards were for the HP -75 and HP - 71B used. Texas Instruments took over this type of storage in the models SR -52 ( 1975), and TI- 59th

At this time, permanent memory was not yet available and the memory chips correspondingly small failed (HP- 65: 100 bytes; HP-67/97: 224 bytes, HP -41C in the basic equipment 448 bytes ), this was the only way, programs and to secure data even after the power of the computer to share with owners of identical computer or distribute commercially.

Examples

The picture shows three magnetic cards Hewlett- Packard, which were for the models HP -65, HP -41 and HP-67/97 in use ( the one cent coin used for size comparison ):

The magnetic layer is on the back. The technology consists of a read head ( related to former cassette recorder ), who wrote two tracks. Because these tracks towards the middle ran and did not fill the entire magnetic card, you could turn the card over and insert the other end for writing (see the marks 1 and 2 on the maps). An engine was responsible for the smooth forward the map and led them past the read head.

In the early 1980s offered HP will provide HP -71 to which had long cards, but did without motor. Thus, energy consumption fell significantly, especially since the former NiCd batteries were much lower than the current capacity and were discharged in accordance quickly when the engine is operating.

Cutting off the corners resulted in a write protection, according trimmed cards could only be overridden by additional measures.

The term " magnetic card " is also common for magnetic stripe cards according to ISO 7810.