A data medium consisting of a card that is partly or completely
coated on one side with ferromagnetic film on which data can be encoded and read
(see card reader). The credit card is one example, the encoding being restricted
to a single strip that can contain three tracks. Other sizes of card have been
used as interchangeable media in data-processing and word-processing
applications. The most widely used example of a word-processing application is
the IBM magnetic card. In the late 1960s a number of mass storage devices were
designed in which large magnetic cards were filed and retrieved automatically.
These were superseded by automated tape libraries and magnetic disk stores.