WOM may refer to: Word of mouth, a term in marketing. ...

Write Only Memory (WOM)

Write only memory is the antithesis of read-only memory (ROM). By definition, a WOM is a memory device which can be written but never read. Since there seems to be no obvious utility for such a memory circuit, from which data cannot be retrieved, the concept is most often used as a joke or a metaphor for a failed memory device. Antithesis (Greek for setting opposite, from against + position) means a direct contrast or exact opposition to something. ... Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. ... A joke is a short story or series of words spoken or communicated with the intent of causing laughter or being found humorous by either listener/reader or performer/writer. ... This article is about metaphor in literature and rhetoric. ...

The Signetics original

Out of frustration with the long and seemingly useless chain of approvals required of component specifications, during which no actual checking seemed to occur, an engineer at Signetics once created a specification for a write-only memory and included it with a bunch of other specifications to be approved. This inclusion came to the attention of Signetics management only when regular customers started calling and asking for pricing information. Signetics published a corrected edition of the data book and requested the return of the 'erroneous' ones. Signetics, once a major player in semiconductor manufacturing, made a variety of devices which included integrated circuits, bipolar and MOS, the Dolby circuit, logic, memory and analog circuits and Motorola clone CPUs, some of which were included in the first Atari video games. ...

Later, in 1972, Signetics bought a double-page spread in the April issue of Electronics and used the spec as an April Fool's Day joke. Instead of the more conventional characteristic curves, the 25120 "fully encoded, 9046 x N, Random Access, write-only-memory" data sheet included diagrams of "bit capacity vs. Temp.", "Iff vs. Vff", "Number of pins remaining vs. number of socket insertions", and "AQL^{[1] [2]} vs. selling price". The 25120 required a 6.3 VAC V_ff (vacuum tube filament) supply, a +10V V_cc (double the Vcc of standard TTL logic of the day), and V_dd of 0V (ie. ground), ±2%.^[3] Electronics, an American trade journal published until 1995, was best known for publishing the April 19, 1965 article by Intel co-founder Gordon Moore in which he outlined what came to be known as Moores Law. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Structure of a vacuum tube diode Structure of a vacuum tube triode In electronics, a vacuum tube, electron tube, or (outside North America) thermionic valve or just valve, is a device used to amplify, switch or modify a signal by controlling the movement of electrons in an evacuated space. ... A Motorola 68000-based computer with various TTL chips. ...

Practical uses

Just because data written to a device cannot be read back after it is written, does not mean that the data is lost or useless. In fact there are many real world applications of the WOM concept at the register level: Register or registration may mean: Registration (or licensing) is required of a number of occupations and professions where maintenance of standards is required to protect public safety. ...

• Trusted computing microcontrollers where the programmer does not want any one else to read the contents of the program on the microcontroller. An example is the feature found in certain microPIC controllers where the EEPROM memory can be set to write-only mode so that the chip can be programmed and the program can run, but the program can not be read from the chip by an external programmer. To prevent a malicous user from blindly modifying the program to output the EEPROM memory, these chips must be completely erased before the EEPROM can be written to again. This setup would however, allow internal reading of the memory.

• Control flags inside a CPU or an I/O controller, such that the data written into a register controls the device (or process) in some way, without being explicitly read back, or even accessible to the device that wrote it.

• Overlaid complementary register pairs (or memory locations) which are mapped to the same physical address, such that one register is always READ only while the other register is always WRITE only. This was common practice in early I/O controllers and microprocessor memory mapping schemes, in order to save hardware and memory address space. The obvious problem with such a mapping scheme, is that the data-writer cannot verify, modify nor reuse the written data in any way, unless he keeps a backup copy of the register's contents within R/W memory. When two copies of the data are required for normal operation, hardware and memory address space are no longer saved. More importantly, the consequent data write event duplication means that register writes are no longer atomic (Atomicity), which can lead to major headaches and status synchronization problems within interrupt driven applications.

• Some devices are naturally used as WOM in one context and ROM in another. Airplane black-boxes and other types of safety data recorders, for example, are typically write only during normal circumstances and read only after an accident. Another way of looking at this is WOM+ROM=R/W, where the reading and writing are done by different entities at different times. (This is NOT the same concept as the overlaid register pairs described in the previous paragraph.)

• Other devices are naturally WOM as far as a computer is concerned. They translate signals to a form that the writer cannot read (but usually either people or other machines can). A printer is an example of this type of device.

• Finally, it should be noted that (just like) the term ROM, which does NOT mean "read only, never written" but rather: "Initialized once and then read only", the term WOM could be construed as meaning "write only, but finalized later (i.e. read or applied)", so the ROM/ WOM concepts can be seen as complimentary or anti-symmetrical:
  
  • ROM = W_initial/ ROM
  • WOM = WOM/ R_final

• Also see ROM, PROM, EPROM, EEPROM (a.k.a. E²PROM), NOVRAM^[4]

Logo of Trusted Computing Group, an initiative to implement Trusted Computing Trusted Computing (commonly abbreviated TC) is a technology developed and promoted by the Trusted Computing Group (TCG). ... The Flags (Far North Liquids and Associated Gas System) Pipeline is used to transport gas from the following Oil platforms: Cormorant A North Cormorant North West Hutton Ninian Central Ninian North & South Brent A, B, C and D Tern Magnus Thistle Murchison Statfjord Heather The pipeline is a 36 inch... CPU can stand for: in computing: Central processing unit in journalism: Commonwealth Press Union in law enforcement: Crime prevention unit in software: Critical patch update, a type of software patch distributed by Oracle Corporation in Macleans College is often known as Ash Lim. ... This article is about the computer interface. ... The word complement (with an e in the second syllable, not to be confused with a different word, compliment with an i) has a number of uses. ... This article is about the computer interface. ... A microprocessor is a programmable digital electronic component that incorporates the functions of a central processing unit (CPU) on a single semiconducting integrated circuit (IC). ... In computer science, atomicity implies indivisibility and irreducibility, so an atomic operation must appear to be performed entirely or not at all. ... Read-only memory (usually known by its acronym, ROM) is a class of storage media used in computers and other electronic devices. ... This article or section does not cite any references or sources. ... EPROM. The small quartz window admits UV light during erasure. ... An EEPROM (also called an E2PROM)[] or Electronically Erasable Programmable Read-Only Memory, is a non-volatile storage chip used in computers and other devices to store small amounts of volatile (configuration) data. ...

References

1. ^ http://www.sixsigmaspc.com/dictionary/AQL-acceptablequalitylevel.html Acceptable Quality Level
2. ^ http://dictionary.reference.com/browse/AQL AQL
3. ^ http://www.catb.org/~esr/jargon/html/W/write-only-memory.html WOM in the Jargon File v. 4.4.7
4. ^ http://www.intersil.com/data/an/AN1146.pdf INTEL, NOVRAM

The Jargon File is a glossary of hacker slang. ...

External links

• Microsoft MVP: Write only registers
• WriteOnly/ ReadOnly Register pairs
• Write-only language
• FINO — First In, Never Out scheduling algorithm
• /dev/null
• Official Signetics 25120 Data Sheet (PDF).

A write-only language is a programming language with the attribute that programs written in it are more easily scrapped and re-written than modified. ... In computer science, FINO is a jocular scheduling algorithm. ... In Unix-like operating systems, /dev/null or the null device is a special file that discards all data written to it, and provides no data to any process that reads from it. ...

This article includes material from the Jargon File. The Jargon File is a glossary of hacker slang. ...