Write-only memory is the opposite of read-only memory. By some definitions, a WOM is a memory device which can be written but never read. Initially there seemed to be no practical use for a memory circuit from which data could not be retrieved. The concept is still often used as a joke or a euphemism for a failed memory device. The first use of the term is generally attributed to Signetics in 1972. Signetics published some write-only memory literature as the result of an inside practical joke, which is frequently referenced within the electronics industry, a staple of software engineering lexicons, and included in collections of the best hoaxes.
Signetics
The datasheet was created "as a lark" by Signetics engineer John G 'Jack' Curtis and was inspired by a fictitious and humorous vacuum tube datasheet from the 1940s. It was seen as "an icebreaker" and was deliberately included in the Signetics catalog. Roy L Twitty, a Signetics PR person, released a tongue-in-cheek press release touting the WOM on April 1, 1973. Instead of the more conventional characteristic curves, the 25120 "fully encoded, 9046×N, Random Access, write-only-memory" data sheet included meaningless diagrams of "bit capacity vs. Temp.", "Iff vs. Vff", "Number of pins remaining vs. number of socket insertions", and "AQL vs. selling price". The 25120 required a 6.3 VAC Vff supply, a +10 Vcc, and Vdd of 0±2% volt. It was specified to run between 0 and −70°C.
In 1982, Apple published their official Apple IIe Reference Manual, which included two references to write-only memory: On page 233:
bit bucket: The final resting place of all information; see write-only memory.
On page 250:
write-only memory: A form of computer memory into which information can be stored but never, ever retrieved, developed under government contract in 1975 by Professor Homberg T. Farnsfarfle. Farnsfarfle's original prototype, approximately one inch on each side, has so far been used to store more than 100 trillion words of surplus federal information. Farnsfarfle's critics have denounced his project as a six-million-dollar boondoggle, but his defenders point out that this excess information would have cost more than 250 billion dollars to store in conventional media.
Book
The 1995 Computer Contradictionary book discusses EWOM, or Erasable Write-Only Memory, a memory copyrighted by IBM, which allows the data to be written to and then erased, for memory re-use. With the explosive growth of the amount of video data available both online and in private use, there emerged a common joke that video tapes and other video media are "write only memory", because without efficient means of search and retrieval for video data archives, very little is viewed after recording.
Other members of the family
The 25120 WOM joined a family of equally-useless parts made before and since. These include the dark bulb, dark-emitting diode, WAS gate, and Inoperational Amplifier. Grandparents were the Umac 606 Infernal Anode Phantasatron and the Electrovoice Rearaxial Softspeaker. Note that the Phantastron is a real, if obsolete, circuit for generating precision sawtooth waves.
