single assignment


A property of variables in a functional language. If a variable is only assigned a value once then an instance of that variable is thereafter semantically equivalent to the value. SISAL is an example of a language with this property.

See also zero assignment.

Last updated: 2003-12-22

single assignment language


Any programming language with the single assignment property.

Last updated: 2007-03-21


Connected to only one of the two rings of an FDDI network. This is the kind of connection normally used for a host computer, as opposed to routers and concentrators which are normally "dual-attached".

Last updated: 1994-12-13

Single Connection Attach


(SCA, "Single Connector Attachment") A non-standard type of SCSI connector, used mostly by OEMs, which carries both power and data on one 80-pin connector. SCA SCSI drives tend to be cheaper but use with standard SCSI cables requires an adaptor and external termination.

Last updated: 2003-06-21

Single Connector Attachment

Single Connection Attach

Single Data Rate Random Access Memory


(SDR-RAM, SDR-SDRAM, Single Data Rate Synchronous Dynamic Random Access Memory) RAM or SDRAM that transfers data on only one clock transition (0-1 or 1-0), in contrast to DDR-RAM.

Last updated: 2001-05-24

Single Data Rate Synchronous Dynamic Random Access Memory

Single Data Rate Random Access Memory

Single Document Interface


(SDI) A limitation applying to an application program that only shows a single windows giving a view of one document at a time.

The opposite is Multiple Document Interface (MDI).

Last updated: 1999-03-30



(From telegraphy) A full-duplex link with one telegrapher at each end, transmitting alternately in each direction.

Last updated: 2000-03-30

Single Edge Contact


(SEC) The type of cartridge in which a Pentium II is packaged.

[Other uses?]

Last updated: 1999-02-15

Single Edge Contact Cartridge


(SEC, SECC) The cased daughterboard housing Intel's Pentium II, Pentium III, and Xeon microprocessors.

A SECC fits into a Slot 1 or Slot 2 connector.

[SECC 2?]

Last updated: 1999-08-05

Single Edge Processor Package


(SEPP) The caseless daughterboard containing Intel's Celeron processor. A SEPP fits into a Slot 1 connector.

Last updated: 1999-08-04

single-electron transistor

quantum dot

Single Electron Tunneling


(SET) A New electrical standard for capacitance.

SET devices can be used to construct circuits which process information by manipulating individual electrons. SET devices are small, dissipate little power, and can detect exquisitely small quantities of charge. The small size and low power dissipation of SET circuits makes them potentially useful for the Information Technology industry.

Last updated: 1999-01-06

Single Electron Tunneling Technology


A neural network hardware concept based on single electron tunneling. Single electron tunneling transistors have some properties which make them attractive for neural networks, among which their small size, low power consumption and potentially high speed.

Simulations have been performed on some small circuits of SET transistors that exhibit functional properties similar to those required for neural networks.

[Proceedings of the Fifth International Conference on Microelectronics for Neural Networks and Fuzzy Systems (MicroNeuro '96). Martijn J. Goossens, Chris J.M. Verhoeven, and Arthur H.M. van Roermund].

Last updated: 1999-01-06

single ended


An electrical connection where one wire carries the signal and another wire or shield is connected to electrical ground. This is in contrast to a differential connection where the second wire carries an inverted signal.

Single Image Random Dot Stereogram


(SIRDS, originally "autostereogram") A stereogram composed of (coloured) dots which when viewed correctly appears three-dimensional. SIRDs were invented by Dr. Christoper Tyler, Associate Director of the Smith-Kettlewell Eye Research Institute in San Francisco (1999).

FAQ. Nice pictures. Picture Gallery. Vern Hart's SIRDS Gallery. SGI Gallery.

Last updated: 1996-11-06

single inheritance


In object-oriented programming, the restriction that a class can have only one superclass in the class hierarchy.

The opposite is multiple inheritance.

Last updated: 2014-09-06

Single In-line Memory Module


(SIMM) A small circuit board or substrate, typically about 10cm x 2cm, with RAM integrated circuits or die on one or both sides and a single row of pins along one long edge. Several SIMMs are mounted with their substrates at right-angles to the main circuit board (the motherboard). This configuration allows greater packing density than direct mounting of, e.g. DIL (dual in-line) RAM packages on the motherboard. In 1993 one SIMM typically held one or four megabytes, by early 1997 one could hold 8, 16, or 32 MB.

Last updated: 1997-01-05

Single Inline Pin Package


(SIPP) An integrated circuit package with a single line of pins.

Compare Dual Inline Package, Single In-line Memory Module.

Last updated: 1995-03-01

Single Instruction Multiple Data

Single Instruction/Multiple Data

Single Instruction/Multiple Data

(SIMD) (Or "data parallel") The classification under Flynn's taxonomy for a parallel processor where many processing elements (functional units) perform the same operations on different data. There is often a central controller which broadcasts the instruction stream to all the processing elements.

Contrast Multiple Instruction/Multiple Data.

Last updated: 1994-11-04

Single-line Digital Subscriber Line

<communications, protocol>

(SDSL, or Single-pair High Speed Digital Subscriber Line, S-HDSL) A form of Digital Subscriber Line similar to HDSL but providing T1 or E1 connections over a single twisted-pair copper line.

Last updated: 1998-05-18

single-page web application

<web, application>

A web site that behaves more like an application program in that, instead of clicking a link causing the web browser to load a whole new web page, changes of state are performed by JavaScript running in the web browser fetching new content or data from the web server and using it to update (parts of) the existing page. This is often done via a protocol like AJAX. This way of working allows the browser to maintain the user's session state more easily and minimise the amount of data that needs to be downloaded and rendered thus largely eliminating the delay incurred when moving from page to page in a traditional web site.

Gmail is a well-known example of a single-page web application.

Last updated: 2014-11-27

Single-pair High Speed Digital Subscriber Line

Single-line Digital Subscriber Line

single program/multiple data

<parallel, architecture>

(SPMD) A kind of parallel processing where the same program is run on multiple processors. Every instance of the program knows which part of the computation it should perform and the results of the computation are combined somehow.

Last updated: 2002-04-21

single quote


"'" ASCII character 39.

Common names include single quote; quote; ITU-T: apostrophe. Rare: prime; glitch; tick; irk; pop; INTERCAL: spark; ITU-T: closing single quotation mark; ITU-T: acute accent.

Single quote is used in C and derived languages to introduce a single character literal value which is represented internally by its ASCII code. In the Unix shells and Perl single quote is used to delimit strings in which variable substitution is not performed (in contrast to double-quote-delimited strings).

Single quote is often used in text for both open and close single quotation mark and apostrophe. Typesetters use two different symbols - open has a tail going up, close and apostrophe have tails hanging down (like a raised comma). Some people use back quote (`) for open single quotation mark.

Last updated: 1998-04-04

single sign-on


(SSO) Any user authentication system permiting users to access multiple data sources through a single point of entry. Part of an integrated access management framework.

Last updated: 2003-12-31

single sourcing


Using a single original document set to generate dead tree and on-line documentation, and usually also on-line help. In practice, it most often refers to a FrameMaker file set with conditional text which, when the conditions are set appropriately, allows you to create variants of the original document (e.g., for a product that runs on different Unix platforms) as well as for different media -- typically task-oriented on-line help to be accessed under Microsoft Windows or from a web browser, linear printed document, and HTML delivered via the WWW and/or CD-ROM.

single static assignment


(Also known as SSA form) A special form of code where each variable has only one single definition in the program code. "Static" comes from the fact that the definition site may be in a loop, thus dynamically executed several times.

SSA form is used for program optimization or static analysis and optimisation.

Last updated: 2003-04-12

singleton variable


A variable which is only referred to once in a piece of code, probably because of a programming mistake. To be useful, a variable must be set and read from, in that order. If it is only referred to once then it cannot be both set and read.

There are various exceptions. C-like assignment operators, e.g. "x += y", read and set x and return its new value (they are abbreviations for "x = x+y", etc). A function argument may be passed only for the sake of uniformity or to support future enhancements. A good compiler or a syntax checker like lint should report singleton variables but also allow specific instances to be marked as deliberate by the programmer.

Last updated: 1997-12-20

Single Virtual Storage


Nearby terms:

sine wavesingle assignmentsingle assignment languagesingle-attached

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