Write Only Memory
Encyclopedia
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 is no practical use for a memory circuit from which data cannot be retrieved, the concept is most often used as a joke
or a euphemism
for a failed memory device.
Signetics unintentionally published 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.
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' literature.
Later, in 1972, Signetics bought a double-page spread in the April issue of Electronics
and used the specification 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 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 (vacuum tube
filament) supply, a +10 Vcc (double the Vcc of standard TTL
logic of the day), and Vdd of zero volts (i.e. ground), ±2%.
, and many computer operating systems provide a pseudo-device which accepts input but does nothing with it; that is, it ignores or discards the data. This is a useful destination for directing unwanted output, such as expected or uninteresting error messages. Unix and Linux provide /dev/null
, CP/M and Microsoft's MSDOS and Windows provide NUL:
, and OpenVMS provide NL: and other variants. Most operating systems permit opening the null device for input, though attempts to read from it always receive an end-of-file
indication.
Antithesis
Antithesis is a counter-proposition and denotes a direct contrast to the original proposition...
of read-only memory
Read-only memory
Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...
(ROM). By definition, a WOM is a memory device which can be written but never read. Since there is no practical use for a memory circuit from which data cannot be retrieved, the concept is most often used as a joke
Joke
A joke is a phrase or a paragraph with a humorous twist. It can be in many different forms, such as a question or short story. To achieve this end, jokes may employ irony, sarcasm, word play and other devices...
or a euphemism
Euphemism
A euphemism is the substitution of a mild, inoffensive, relatively uncontroversial phrase for another more frank expression that might offend or otherwise suggest something unpleasant to the audience...
for a failed memory device.
Signetics unintentionally published 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.
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 SigneticsSignetics
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. They developed microprocessors like the 2650, the bipolar 8X300 and had licensed Motorola 68000...
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' literature.
Later, in 1972, Signetics bought a double-page spread in the April issue of Electronics
Electronics (magazine)
Electronics was an American trade journal that covered the radio industry and its later spin-offs in the mid to late 1900s. Published by McGraw-Hill and Penton Publishing , its first issue was dated in April 1930....
and used the specification 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 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 (vacuum tube
Vacuum tube
In electronics, a vacuum tube, electron tube , or thermionic valve , reduced to simply "tube" or "valve" in everyday parlance, is a device that relies on the flow of electric current through a vacuum...
filament) supply, a +10 Vcc (double the Vcc of standard TTL
Transistor-transistor logic
Transistor–transistor logic is a class of digital circuits built from bipolar junction transistors and resistors. It is called transistor–transistor logic because both the logic gating function and the amplifying function are performed by transistors .TTL is notable for being a widespread...
logic of the day), and Vdd of zero volts (i.e. ground), ±2%.
Bit buckets
In computers, there are many practical uses for a destination to write data which does not retain it. A common term among engineers is bit bucketBit bucket
In computing, the bit bucket is jargon for where lost computerized data has gone, by any means; any data which does not end up where it is supposed to, being lost in transmission, a computer crash, or the like, is said to have gone to the bit bucket — that mysterious place on a computer where...
, and many computer operating systems provide a pseudo-device which accepts input but does nothing with it; that is, it ignores or discards the data. This is a useful destination for directing unwanted output, such as expected or uninteresting error messages. Unix and Linux provide /dev/null
/dev/null
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 ....
, CP/M and Microsoft's MSDOS and Windows provide NUL:
NUL:
In the CP/M, DOS, and Microsoft Windows operating systems, the name NUL: or simply NUL designates a special file that discards all data written to it , and provides no data to any process that reads from it .In the Windows NT system and its successors, it is named \Device\Null internally, and the...
, and OpenVMS provide NL: and other variants. Most operating systems permit opening the null device for input, though attempts to read from it always receive an end-of-file
End-of-file
In computing, end of file is a condition in a computer operating system where no more data can be read from a data source...
indication.