Gourt Home::Gourt :: Write Once Read Many
WORM means Write Once, Read Many (or Write Once Read Multiple times). It is sometimes used when discussing computer storage media that can be written to once, but read from multiple times.
There are two types of WORM storage media: those that physically can be written only once (examples of such storage media are CD-R and DVD-R, or electronic circuits such as PROMs) and media that enables WORM capability by using electronic keys or other measures to prevent rewriting. The reasoning behind this artificial hampering of technical capability in the latter case can be found in regulatory authorities requiring certain data archival standards where information has to be reliably kept and made available over a long period of time (an example would be the Securities Exchange Commission).
Media which intentionally restricts writing to one time only: Super DLT (Super DLT II media is in fact used for standard and WORM operations, as demanded by the user), LTO, AIT and various hard disk drive based systems. Software write protection is less secure and some of these systems actually enable recycling of pre-used media.
Paper has for centuries been a semi-WORM storage medium. (It can be erased, but unlike parchment it's not practical to do so. See also Palimpsest.)
Other meanings
WORM should not be confused with worm (not in capitals) (a self-replicating computer program, similar to a computer virus).
A Write Once Read Many or WORM drive is a magneto-optic data storage device. These drives are used in applications where the same information is read a large number of times, but still must be rewritten occasionally; digital archives for example. A WORM drive works on a similar principle as a magneto-optical drive, but fills the role of a hard disk rather than a floppy disk. The drive is able to achieve a large number of read cycles because magnetic information is read remotely using a laser beam, eliminating the need for a magnetic head to approach the storage medium; a conventional magnetic head is used only when new data must be written.
The eccentric Oliver Heaviside would sign correspondences "WORM" near the end of his life.
See also
WORM | WORM | Write Once Read Many | WORM
"Write Once Read Many"