un from FOLDOC

Transforming a curried function of the form f x y z = ... to one of the form f (x, y, z) = ... , i.e. all arguments are passed as one tuple.

Last updated: 1998-07-02

undefined

The value of a variable that has not been set or a function that does not return anything. In some programming languages, e.g. Perl, JavaScript, undefined is a named constant that can be used to explicitly set a variable or return undefined or can be passed as an actual argument. Other languages, e.g. Java, call it "null", but note that the null in relational database programming is subtly different.

Many languages provide a built-in function to test whether an expression is undefined, e.g. Perl's defined() function.

Attempting to operate on an undefined value, e.g. add it to a number or append it to a string, may either raise an error or result in the undefined value being converted (cast) to some appropriate value, e.g. false, zero or empty string, according to the type of expression.

This definition is an example of a paradox.

Last updated: 2012-12-02

undefined external reference

[Unix] A message from Unix's linker, ld. Used in speech to flag loose ends or dangling references in an argument or discussion.

underflow

(or "floating point underflow", "floating underflow", after "overflow") A condition that can occur when the result of a floating-point operation would be smaller in magnitude (closer to zero, either positive or negative) than the smallest quantity representable. Underflow is actually (negative) overflow of the exponent of the floating point quantity. For example, an eight-bit twos complement exponent can represent multipliers of 2^-128 to 2^127. A result less than 2^-128 would cause underflow.

Depending on the processor, the programming language and the run-time system, underflow may set a status bit, raise an exception or generate a hardware interrupt or some combination of these effects. Alternatively, it may just be ignored and zero substituted for the unrepresentable value, though this might lead to a later divide by zero error which cannot be so easily ignored.

Last updated: 2006-11-09

Undernet

An Internet Relay Chat network dating from the 1990s, when it broke away from the main (still larger) IRC network, EFNet.

http://undernet.org/.

The History of the Undernet.

Last updated: 1995-11-09

underscore

<character>

_, ASCII 95.

Common names: ITU-T: underline; underscore; underbar; under. Rare: score; backarrow; skid; INTERCAL: flatworm.

under the hood

[hot-rodder talk] 1. The underlying implementation of a product (hardware, software, or idea). Implies that the implementation is not intuitively obvious from the appearance, but the speaker is about to enable the listener to grok it. "Let's now look under the hood to see how ...."

2. Can also imply that the implementation is much simpler than the appearance would indicate: "Under the hood, we are just fork/execing the shell."

3. Inside a chassis, as in "Under the hood, this baby has a 40MHz 68030!"

1. Ente Nazionale Italiano di Unificazione.

undocumented feature

feature

U-NET Limited

A dial-up Internet access provider based in Warrington, UK. Speeds 4800 - 28.8kbps. The currently support Microsoft Windows and RISC OS users. For 12 pounds to join and 12 pounds per month or 100 pounds per year you get a full SLIP account with a pernament IP address and POP3 electronic mail account. Membership includes a disk with Mosaic, Eudora, Trumpet2, Newsreader, FTP and Telnet and full Internet access. Users can choose their own user name and hostname. Allows some extra services such as more than one POP3 account per access account. User name is significant so that a company can have accounts with the same hostname (i.e. their company name) but the mail going to diffent machines. Mail in users POP3 account is accessible from anywhere not just via the dial-up connection. On your next business trip you can still check your e-mail (provided you can get onto the Internet).

http://u-net.com/.

E-mail: <[email protected]>.

Last updated: 1994-11-18

unfold

inline

unfold/fold

A program transformation where a recursive call to a function is unfolded to an instance of the function's body and then later an instance of the function's body is replaced by a call. E.g.

 sumdouble l = sum (double l)

 double l = case l of
            []   -> []
 	   x:xs -> 2*x + double xs

 ==> (unfold double)

 sumdouble l = sum (case l of
 	           []   -> []
 	    x:xs -> 2*x : double xs)

 ==> (distribute over case)

 sumdouble l = case l of
 	      []   -> sum []
 	      x:xs -> sum (2*x : double xs)

 	==> (unfold sum)

 sumdouble l = case l of
 	      []   -> 0
 	      x:xs -> 2*x + sum (double xs)

 	==> (fold sumdouble)

 sumdouble l = case l of
 	      []   -> 0
 	      x:xs -> 2*x + sumdouble xs

Last updated: 1994-11-03

UNI

<standard, body>

2. User Network Interface.

Last updated: 1999-02-01

unicast

COMmon Algorithmic Language

Sending packets to a single destination, used in contrast to broadcast or multicast. The term is generally only used when talking about low level communications, typically at the network layer, e.g. Internet Protocol.

Last updated: 2008-06-23

Unicode

<character>

1. A 16-bit character set standard, designed and maintained by the non-profit consortium Unicode Inc.

Originally Unicode was designed to be universal, unique, and uniform, i.e., the code was to cover all major modern written languages (universal), each character was to have exactly one encoding (unique), and each character was to be represented by a fixed width in bits (uniform).

Parallel to the development of Unicode an ISO/IEC standard was being worked on that put a large emphasis on being compatible with existing character codes such as ASCII or ISO Latin 1. To avoid having two competing 16-bit standards, in 1992 the two teams compromised to define a common character code standard, known both as Unicode and BMP.

Since the merger the character codes are the same but the two standards are not identical. The ISO/IEC standard covers only coding while Unicode includes additional specifications that help implementation.

Unicode is not a glyph encoding. The same character can be displayed as a variety of glyphs, depending not only on the font and style, but also on the adjacent characters. A sequence of characters can be displayed as a single glyph or a character can be displayed as a sequence of glyphs. Which will be the case, is often font dependent.

See also Jörgen Bettels and F. Avery Bishop's paper Unicode: A universal character code.

Last updated: 2002-08-06

<language>

2. A pre-Fortran on the IBM 1130, similar to MATH-MATIC.

[Sammet 1969, p.137].

Last updated: 2004-09-14

UniCOMAL

Unicorny

<humour, programming>

A feature that's so early in the planning stages that it might as well be imaginary.

[Dodgy Coder].1

Last updated: 2013-06-17

unicos

A Unix variant for Cray computers.

[More details?]

Last updated: 1994-12-06

Uniface

<database, programming, product>

1. A 4GL development environment and system integration tool marketed by Compuware. Uniface is database independent, with interfaces to more than 14 database management systems and file retrieval systems including DB2, IMS, SQL Server, Oracle, RDB, Sybase. It is currently supported on MS Windows (98, ME, NT, 2000, XP, 2003), various Unix flavours, Linux, OpenVMS, IBM iSeries (AS/400), IBM zSeries (MVS) and various web servers. Uniface can integrate with SAP, COM, Java, BEA Tuxedo, CICS, and various CORBA implementations.

Uniface user group Germany. Profesional Uniface Users Universe. Free tutorials.

<text>

2. Synonym of bitmap font.

Last updated: 1999-01-05

unification

Universal Naming Convention

The generalisation of pattern matching that is the logic programming equivalent of instantiation in logic. When two terms are to be unified, they are compared. If they are both constants then the result of unification is success if they are equal else failure. If one is a variable then it is bound to the other, which may be any term (which satisfies an "occurs check"), and the unification succeeds. If both terms are structures then each pair of sub-terms is unified recursively and the unification succeeds if all the sub-terms unify.

The result of unification is either failure or success with a set of variable bindings, known as a "unifier". There may be many such unifiers for any pair of terms but there will be at most one "most general unifier", other unifiers simply add extra bindings for sub-terms which are variables in the original terms.

Last updated: 1995-12-14

Unified Han

Han character

Unified Modeling Language

<language>

(UML) A non-proprietary, third generation modelling language. The Unified Modeling Language is an open method used to specify, visualise, construct and document the artifacts of an object-oriented software-intensive system under development. The UML represents a compilation of "best engineering practices" which have proven successful in modelling large, complex systems.

UML succeeds the concepts of Booch, OMT and OOSE by fusing them into a single, common and widely usable modelling language. UML aims to be a standard modelling language which can model concurrent and distributed systems.

UML is not an industry standard, but is taking shape under the auspices of the Object Management Group (OMG). OMG has called for information on object-oriented methodologies, that might create a rigorous software modelling language. Many industry leaders have responded in earnest to help create the standard.

unifier

The unifier of a set of expressions is a set of substitutions of terms for variables such that the expressions are all equal.

See also most general unifier, unification.

Last updated: 1994-12-06

UNIFORM

An intermediate language developed for reverse engineering both COBOL and Fortran.

["The REDO Compendium", H. van Zuylen ed, Wiley 1993].

Last updated: 1994-12-06

Uniform Naming Convention

Uniform Resource Citation

<web>

(URC) A set of attribute/value pairs describing an object. Some of the values may be URIs of various kinds. Others may include, for example, athorship, publisher, datatype, date, copyright status and shoe size. A URC is not normally considered as a string, but a set of fields and values with some defined free formatting.

Last updated: 1995-03-24

Uniform Resource Locater

Uniform Resource Locator

<web>

(URL, previously "Universal") A standard way of specifying the location of an object, typically a web page, on the Internet. Other types of object are described below. URLs are the form of address used on the World-Wide Web. They are used in HTML documents to specify the target of a hypertext link which is often another HTML document (possibly stored on another computer).

Here are some example URLs:

 http://w3.org/default.html
 http://acme.co.uk:8080/images/map.gif
 http://foldoc.org/?Uniform+Resource+Locator
 http://w3.org/default.html#Introduction
 ftp://wuarchive.wustl.edu/mirrors/msdos/graphics/gifkit.zip
 ftp://spy:[email protected]/pub/topsecret/weapon.tgz
 mailto:[email protected]
 news:alt.hypertext
 telnet://dra.com

The part before the first colon specifies the access scheme or protocol. Commonly implemented schemes include: ftp, http (web), gopher or WAIS. The "file" scheme should only be used to refer to a file on the same host. Other less commonly used schemes include news, telnet or mailto (e-mail).

The part after the colon is interpreted according to the access scheme. In general, two slashes after the colon introduce a hostname (host:port is also valid, or for FTP user:passwd@host or user@host). The port number is usually omitted and defaults to the standard port for the scheme, e.g. port 80 for HTTP.

For an HTTP or FTP URL the next part is a pathname which is usually related to the pathname of a file on the server. The file can contain any type of data but only certain types are interpreted directly by most browsers. These include HTML and images in gif or jpeg format. The file's type is given by a MIME type in the HTTP headers returned by the server, e.g. "text/html", "image/gif", and is usually also indicated by its filename extension. A file whose type is not recognised directly by the browser may be passed to an external "viewer" application, e.g. a sound player.

The last (optional) part of the URL may be a query string preceded by "?" or a "fragment identifier" preceded by "#". The later indicates a particular position within the specified document.

Only alphanumerics, reserved characters (:/?#"<>%+) used for their reserved purposes and "$", "-", "_", ".", "&", "+" are safe and may be transmitted unencoded. Other characters are encoded as a "%" followed by two hexadecimal digits. Space may also be encoded as "+". Standard SGML "&<name>;" character entity encodings (e.g. "é") are also accepted when URLs are embedded in HTML. The terminating semicolon may be omitted if &<name> is followed by a non-letter character.

The authoritative W3C URL specification.

Last updated: 2000-02-17

Uniform Resource Name

<web>

(URN, previously Uniform/Universal Resource Number) 1. Any URI which is not a URL.

2. A particular scheme which is currently (1991-4) under development by the IETF, which should provide for the resolution using Internet protocols of names which have a greater persistence than that currently associated with Internet host names or organisations (as used in URLs). Uniform Resource Names will be URI schemes that improve on URLs in reliability over time, including authenticity, replication, and high availability.

When defined, a URN in sense 1 will be an example of a URN in sense 2.

http://w3.org/pub/WWW/Addressing/Addressing.html.

Last updated: 2006-04-18

Uniform Resource Number

Former name for Uniform Resource Name.

Unify

<database, product>

A relational database produced by Unify Corporation.

Last updated: 1995-03-15

unify

<algorithm>

To perform unification.

Last updated: 1995-03-15

Unify Corporation

<company>

Developers of the Unify relational database. At one time, before Sybase, they were a competitor of Oracle, et al.

http://unify.com/.

ftp://ftp.unify.com/.

Last updated: 1995-03-15

Unihan

Han character

uninstaller

A utility program to remove another application program from a computer's disks.

Most commonly found on IBM PCs, as applications tend to leave files in various places on the hard disc, so special software is required to tidy up after them.

Ken Spreitzer <[email protected]> claims to have written the original PC program called "UnInstaller", first licensed to MicroHelp and now (Feb 1998) sold by CyberMedia.

Compare with installer.

Last updated: 1998-02-09

uninteresting

<jargon>

1. Said of a problem that, although nontrivial, can be solved simply by throwing sufficient resources at it.

2. Also said of problems for which a solution would neither advance the state of the art nor be fun to design and code.

Hackers regard uninteresting problems as intolerable wastes of time, to be solved (if at all) by lesser mortals. *Real* hackers (see toolsmith) generalise uninteresting problems enough to make them interesting and solve them - thus solving the original problem as a special case (and, it must be admitted, occasionally turning a molehill into a mountain, or a mountain into a tectonic plate).

See WOMBAT, SMOP. Compare toy problem. Oppose interesting.

Last updated: 1995-03-10

Uninterruptible Power Supply

<hardware>

(UPS) A battery powered power supply unit that is guaranteed to provide power to a computer in the event of interruptions in the incoming mains electrical power. Different rating UPSs will provide power for different lengths of time.

Modern UPSs connect to the computer's serial port and provide information such as battery time remaining, allowing the computer to shut down gracefully before complete loss of power.

Last updated: 1996-12-11

union

<theory>

1. An operation on two sets which returns the set of all elements that are a member of either or both of the sets; normally written as an infix upper-case U symbol. The operator generalises to zero or more sets by taking the union of the current partial result (initially the empty set) with the next argument set, in any order.

For example, (a, b, c) U (c, d, e) = (a, b, c, d, e)

2. A type whose values may be of one of a number of other types, the current type depending on conditions that are only known at run-time. A variable of union type must be allocated sufficient storage space to hold the largest component type. Some unions include extra information to say which type of value the union currently has (a "tagged union"), others rely on the program to keep track of this independently.

A union contrasts with a structure or record which stores values of all component types at once.

<database>

3. An SQL operator that concatenates two result sets, that must have the same number and types of columns. The operator may be followed by the word "ALL" to indicate that results that appear in both sets should appear twice in the output.

Last updated: 2002-02-26

Unipalm Group plc

<company>

A company floated in March 1994.

http://unipalm.co.uk/index.html.

Last updated: 1996-12-11

Unipress Software, Inc.

<company>

A developer and distributor of Unix software. They produce PC-UNIX connectivity software, development tools and applications and provide technical support and maintenance, porting services, training and consulting.

http://unipress.com/.

Last updated: 1996-12-11

uniprocessor

<processor>

(From "uni" - one) A computer with a single central processing unit, in contrast to a parallel processor. Most personal computers are currently (March 1997) uniprocessors. Some more expensive computers, typically servers, have multiple processors to provide increased throughput.

Last updated: 1997-03-23

UNIQUE

<language>

A portable job control language.

["The UNIQUE Command Language - Portable Job Control", I.A. Newman, Proc DATAFAIR 73, 1973, pp. 353-357].

Last updated: 1994-11-22

Unique ID Listing

<messaging>

(UIDL) A system used by POP3 electronic mail servers to uniquely identify a mail message. Normally, a message is identified by its position in the list of messages but this will change when an earlier message is deleted. The UIDL is a fixed string of characters which is unique to the message. The UIDL of a message never changes and will never be reused, even when the message has been deleted from the user's mailbox.

RFC 1725.

Last updated: 1997-04-16

unique key

<database>

A key which identifies only one body of information out of several.

Last updated: 1997-04-26

unique sales point

<product>

(USP) A feature that the salesman hopes will convince you to buy his product instead of another.

Last updated: 1999-10-21

Unir Tech

<company>

The company with the exclusive license from Bell Labs to distribute C+@. Unir is owned and operated by well-known anti-IETF ranter, Jim Fleming.

Telephone: +1 (800) 222-8647.

Last updated: 2002-05-19

UNISAP

An early system on UNIVAC I or II.

[Listed in CACM 2(5):16 (May 1959)].

Last updated: 1994-11-22

Unisys Corporation

<company>

The company formed in 1984-5 when Burroughs Corporation merged with Sperry Corporation. This was when the phrase "dinosaurs mating" was coined.

Unisys is one of the largest providers of information services, technology, and software in the world. They employ about 49,000 people and do business in some 100 countries. In 1994 about 80 percent of revenue was derived from commercial information systems and services, with the remainder coming from electronic systems and services for the defense market. The defense business was sold to Loral in early 1995. Slightly more than half of Unisys's revenue is from business in the United States.

They specialise in providing business-critical solutions, based on open information networks, for organisations that operate in transaction-intensive environments. These organisations include financial services companies, airlines, telecommunications companies, government agencies, and other commercial enterprises.

In August 1994, quarterly sales were $1799M and profits $50M.

http://unisys.com/.

Last updated: 1995-03-21

United Kingdom Education and Research Networking Association

<company>

(UKERNA or JANET (UK)) The trading name for JNT Association.

Last updated: 2016-04-12

United Kingdom Unix Users Group

UKUUG Ltd.

United Technologies Research Cente

(UTRC) http://utrcwww.utc.com/.

Last updated: 1994-11-29

Unit Separator

<character>

(US) ASCII character 31.

Last updated: 1996-06-29

unit testing

<testing>

The type of testing where a developer (usually the one who wrote the code) proves that a code module (the "unit") meets its requirements.

Last updated: 2003-09-24

UNITY

A high-level parallel language.

A translator into MPL is available by ftp://sanfrancisco.ira.uka.de/pub/maspar/maspar_unity.tar.Z.

Univac

<processor, company>

A brand of computer.

There is a historical placard in the United States Census Bureau that has the following, "The Bureau of the Census dedicated the world's first electronic general purpose data processing computer, UNIVAC I, on June 14, 1951. Eckert-Mauchly Computer Corporation".

The Eckert-Mauchly Computer Corporation designed and built Univac. Over the years, rights to the Univac name changed hands several times. Circa 1987, Sperry Univac merged with the Burroughs Corporation to form Unisys Corporation.

Last updated: 1994-11-22

Universal algebra

<logic>

The model theory of first-order equational logic.

Last updated: 1997-02-25

Universal Asynchronous Receiver/Transmitter

<communications, hardware>

(UART) An integrated circuit used for serial communications, containing a transmitter (parallel-to-serial converter) and a receiver (serial-to-parallel converter), each clocked separately.

The parallel side of a UART is usually connected to the bus of a computer. When the computer writes a byte to the UART's transmit data register (TDR), the UART will start to transmit it on the serial line. The UART's status register contains a flag bit which the computer can read to see if the UART is ready to transmit another byte. Another status register bit says whether the UART has received a byte from the serial line, in which case the computer should read it from the receive data register (RDR). If another byte is received before the previous one is read, the UART will signal an "overrun" error via another status bit.

The UART may be set up to interrupt the computer when data is received or when ready to transmit more data.

The UART's serial connections usually go via separate line driver and line receiver integrated circuits which provide the power and voltages required to drive the serial line and give some protection against noise on the line.

Data on the serial line is formatted by the UART according to the setting of the UART's control register. This may also determine the transmit and receive baud rates if the UART contains its own clock circuits or "baud rate generators". If incorrectly formated data is received the UART may signal a "framing error" or "parity error".

Often the clock will run at 16 times the baud rate (bits per second) to allow the receiver to do centre sampling - i.e. to read each bit in the middle of its allotted time period. This makes the UART more tolerant to variations in the clock rate ("jitter") of the incoming data.

An example of a late 1980s UART was the Intel 8450. In the 1990s, newer UARTs were developed with on-chip buffers. This allowed higher transmission speed without data loss and without requiring such frequent attention from the computer. For example, the Intel 16550 has a 16 byte FIFO. Variants include the 16C550, 16C650, 16C750, and 16C850.

The term "Serial Communications Interface" (SCI) was first used at Motorola around 1975 to refer to their start-stop asyncronous serial interface device, which others were calling a UART.

Universal Character Set

<character, standard>

(UCS, ISO/IEC 10646) A 1993 ISO and IEC standard character set, also known as "Universal Multiple-Octet Coded Character Set".

UCS comes in a 16-bit variant called UCS-2 and a 32-bit variant called UCS-4, which is composed of 16-bit UCS-2 "planes". So far only one 16-bit plane has been defined, which is known as the Basic Multilingual Plane.

The implementation of UCS is still in its infancy, though some moves, such as the Java language defining a character to be 16 bits, are suggestive.

[Relationship with Unicode?]

Last updated: 1997-07-04

Universal Communications X

<communications>

(UCX) A software implementation of the ubiquitous TCP/IP suite of communications protocols for Digital Equipment Corporation's OpenVMS operating system.

Users of the UCX product can connect to heterogeneous networks to access and download files, send electronic mail, run and develop applications, and monitor activity.

"Software Product Description, DIGITAL TCP/IP Services for OpenVMS, Version 4.2",.

Last updated: 2000-12-15

Universal Computer Protocol

<communications, protocol>

An earlier form of External Machine Interface (EMI).

Last updated: 2007-09-10

Universal Debugger

<tool, parallel>

(udb) KSR's interactive source level debugger for serial and parallel programs written in KSR, Fortran, KSR C and KSR1 assembly language.

Udb is a source level debugger for testing and debugging serial and parallel programs; it is compatible with GDB and dbx. The user can direct udb either by typing commands or graphically through an X-based window interface; the latter provides simultaneous display of source code, I/O and instructions. For parallel programs, operations can be carried out per-thread.

Home.

Last updated: 1995-05-07

Universal Description, Discovery, and Integration

<standard, protocol>

(UDDI) The service discovery protocol for Web Services through which companies can find one another to conduct business. This standard was unveiled by Ariba, IBM, Microsoft, and 33 other companies in September 2000.

Last updated: 2002-06-28

Universal Disk Format

<storage, standard>

(UDF) A CD-ROM file system standard that is required for DVD ROMs. UDF is the OSTA's replacement for the ISO 9660 file system used on CD-ROMs, but will be mostly used on DVD. DVD multimedia disks use UDF to contain MPEG audio and video streams.

To read DVDs you need a DVD drive, the kernel driver for the drive, MPEG video support, and a UDF driver. DVDs containing both UDF filesystems and ISO 9660 filesystems can be read without UDF support.

UDF can also be used by CD-R and CD-RW recorders in packet writing mode.

Last updated: 1999-09-01

Universal Naming Convention

(UNC) The type of file system path used in Microsoft Windows networking to completely specify a directory on a file server.

The basic format is:

 \\servername\sharename

where "servername" is the hostname or IP address of a network file server, and "sharename" is the name of a shared directory on the server. This is related to the conventional MS-DOS "C:\windows" style of directory name. E.g.

 \\server1\dave

might be set up to point to

 C:\users\homedirs\dave

on a server called "server1".

It is possible to execute a program using this convention without having to specifically link a drive, by running:

\\server\share\directory\program.exe

The undocumented DOS command, TRUENAME can be used to find out the UNC name of a file or directory on a network drive.

Even Microsoft don't know whether UNC stands for "Universal Naming Convention" or "Uniform Naming Convention", both appear on their website, sometimes withing the same document, but with a preference for "Universal".

Last updated: 2008-12-09

universal quantifier

quantifier

Universal Resource Identifier

<web>

(URI, originally "UDI" in some WWW documents) The generic set of all names and addresses which are short strings which refer to objects (typically on the Internet). The most common kinds of URI are URLs and relative URLs.

URIs are defined in RFC 1630.

W3 specification.

Last updated: 1997-07-16

Universal Resource Locator

Uniform Resource Locator

Universal Serial Bus

<hardware, standard>

(USB) An external peripheral interface standard for communication between a computer and external peripherals over an inexpensive cable using biserial transmission.

USB is intended to replace existing serial ports, parallel ports, keyboard, and monitor connectors and be used with keyboards, mice, monitors, printers, and possibly some low-speed scanners and removable hard drives. For faster devices existing IDE, SCSI, or emerging FC-AL or FireWire interfaces can be used.

USB works at 12 Mbps with specific consideration for low cost peripherals. It supports up to 127 devices and both isochronous and asynchronous data transfers. Cables can be up to five metres long and it includes built-in power distribution for low power devices. It supports daisy chaining through a tiered star multidrop topology. A USB cable has a rectangular "Type A" plug at the computer end and a square "Type B" plug at the peripheral end.

Before March 1996 Intel started to integrate the necessary logic into PC chip sets and encourage other manufacturers to do likewise. It was widely available by 1997. Later versions of Windows 95 included support for it. It was standard on Macintosh computers in 1999.

The USB 2.0 specification was released in 2000 to allow USB to compete with Firewire etc. USB 2.0 is backward compatible with USB 1.1 but works at 480 Mbps.

usb.org.

Last updated: 2004-01-31

universal thunk

<programming, operating system>

A software mechanism allowing a Windows 3.1 application to call a 32-bit dynamically linked library (DLL) under Win32s.

The Windows 3.1 application which wants to call an entry in a 32-bit DLL instead calls a corresponding entry in a 16-bit DLL. The programmer must also include code to detect whether the 32-bit DLL is loaded. A 32-bit EXE loads the 32-bit DLL.

Universal Time

<time, standard>

(UT) The mean solar time along the prime meridian (0 longitude) that runs through the Greenwich Observatory outside of London, UK, where the current system originated. UT is tied to the rotation of the Earth in respect to the fictitious "mean Sun".

Greenwich Mean Time (GMT) was measured from Greenwich mean midday until 1925 when the reference point was changed from noon to midnight and the name changed to "Universal Time".

There are three separate definitions, UT0, UT1, and UT2, depending on which corrections have been applied to the Earth's motion. Coordinated Universal Time is kept within 0.9 seconds of UT1, by addition of leap seconds to International Atomic Time.

Last updated: 2001-08-02

Universal Time Coordinated

<time, standard>

An incorrect term for Coordinated Universal Time.

Last updated: 2001-08-01

universe of discourse

<artificial intelligence>

In ontology, the set of all entities that can be represented in some declarative language or other formal system.

Each entity is represented by a name and may have some human-readable description of its meaning. Formal axioms constrain the interpretation and well-formed use of these names.

Last updated: 2005-07-29

University of Arizona

<body, education>

The University was founded in 1885 as a Land Grant institution with a three-fold mission of teaching, research and public service. Today, the University is one of the top 20 research universities in the nation, with a student enrollment of more than 35,000, a faculty and staff of 12,500, and a 345-acre campus.

http://arizona.edu/.

Address: Tucson, Arizona, USA.

University of California at Berkeley

<body, education>

(UCB)

University of Durham

<body, education>

A busy research and teaching community in the historic cathedral city of Durham, UK (population 61000). Its work covers key branches of science and technology and traditional areas of scholarship. Durham graduates are in great demand among employers and the University helps to attract investment into the region. It provides training, short courses, and expertise for industry. Through its cultural events, conferences, tourist business and as a major employer, the University contributes in a wide social and economic sense to the community.

Founded in 1832, the University developed in Durham and Newcastle until 1963 when the independent University of Newcastle upon Tyne came into being. Durham is a collegiate body, with 14 Colleges or Societies which are a social and domestic focus for students. In 1992, the Universities of Durham and Teesside launched University College, Stockton-on-Tees, which has 190 students in the first year.

http://dur.ac.uk/.

Last updated: 1995-03-17

University of East London

<body, education>

(UEL) A UK University with six academic Faculties: Design and The Built Environment, East London Business School, Institute Of Health and Rehabilitation, Faculty Of Science, Social Sciences and Technology.

http://uel.ac.uk/.

Last updated: 1994-11-29

University of Edinburgh

<body, education>

A university in the centre of Scotland's capital. The University of Edinburgh has been promoting and setting standards in education for over 400 years. Granted its Royal Charter in 1582 by James VI, the son of Mary Queen of Scots, the University was founded the following year by the Town Council of Edinburgh, making it the first post-Reformation university in Scotland, and the first civic university to be established in the British Isles.

Known in its early years as King James College, or the Tounis (Town's) College, the University soon established itself internationally, and by the 18th century Edinburgh was a leading centre of the European Enlightenment and one of the continent's principal universities. The University's close relationship with the city in which it is based, coupled with a forward-looking, international perspective, has kept Edinburgh at the forefront of new research and teaching developments whilst enabling it to retain a uniquely Scottish character.

Edinburgh's academics are at the forefront of developments in the study and application of languages, medicine, micro-electronics, biotechnology, computer-based disciplines and many other subjects. Edinburgh's standing as a world centre for research is further enhanced by the presence on and around University precincts of many independently-funded, but closely linked, national research institutes

http://ed.ac.uk/.

Address: Old College, South Bridge, Edinburgh, Scotland EH8 9YL, UK.

Telephone: +44 (131) 650 1000.

Last updated: 1995-12-29

University of Hawaii

<body, education>

A University spread over 10 campuses on 4 islands throughout the state.

http://hawaii.edu/uhinfo.html.

University of Iceland

<body, education>

The Home of Fjolnir.

http://rhi.hi.is/.

Last updated: 1995-03-17

University of London Computing Centre

<body, education>

(ULCC) One of the UK's national high performance computing centres. It provides networking services and large-scale computing facilities which are used by researchers from all over the UK.

ULCC was founded in 1968 to provide a service for education and research. It has been at the forefront of advanced research computing since its foundation, initially providing large-scale CDC-based facilities, then from 1982 to 1991 a national Cray vector supercomputing service. Its high performance computing facilities are now centred on a 6 processor, 4 Gbyte Convex C3860 supercomputer (Neptune) with a Convex C3200 front-end (Pluto).

ULCC is the main site for national and international network connections in the UK. They run the Network Operations and Service Centre for the JANET Internet Protocol Service (JIPS), the largest of the JANET NOCs and various international links and relays on behalf of UKERNA.

ULCC's pilot National Data Repository service provides a network-accessible digital archive and filestore, based on a robotic tape system with 6 terabytes of storage. Although the data is stored on tape, you can access it very quickly, as if it were on-line. It is made available to you via high-speed links to the JANET and SuperJANET networks.

http://ulcc.ac.uk/.

Last updated: 1994-11-29

University of Michigan

<body, education>

A large cosmopolitan university in the Midwest USA. Over 50000 students are enrolled at the University of Michigan's three campuses. The students come from 50 states and over 100 foreign countries. 70% of the University's students graduated in the top 10% of their high school class. 90% rank in the top 20% of their high school class. 60% of the students receive financial aid.

The main Ann Arbor Campus lies in the Huron River valley, 40 miles west of Detroit. The campus boasts 2700 acres with 200 buildings, six million volumes in 23 libraries, nine museums, seven hospitals, hundreds of laboratories and institutes, and over 18000 microcomputers.

http://umich.edu/.

Last updated: 1995-02-23

University of Michigan Digital Library Project

<project>

(UMDL) The University of Michigan's part of the Digital Library Initiative.

University of Minnesota

<body, education>

The home of Gopher.

http://umn.edu/.

Address: Minneapolis, Minnesota, USA.

Last updated: 1995-01-30

University of Nijmegen

<body, education>

Katholieke University of Nijmegen (KUN), Nijmegen, the Netherlands.

KUN's Computing Science Institute. is known for the Clean, Comma, Communicating Functional Processes, and GLASS projects.

http://kun.nl/.

Last updated: 1995-11-07

University of Pennsylvania

<body, education>

The home of ENIAC and Machiavelli.

http://upenn.edu/.

Address: Philadelphia, PA, USA.

[More info?]

Last updated: 1995-02-21

University of Tasmania

<body, education>

ftp://ftp.utas.edu.au/.

Last updated: 1995-01-25

University of Twente

<body, education>

A university in the east of The Netherlands for technical and social sciences. It was founded in 1961, making it one of the youngest universities in The Netherlands. It has 7000 students studying Applied Educational Science; Applied Mathematics; Applied Physics; Chemical Technology; Computer Science; Electrical Engineering; Mechanical Engineering; Philosophy of science, Technology and Society; Educational Technology.

http://nic.utwente.nl/uthomuk.htm.

Last updated: 1995-04-16

Unix

/yoo'niks/ (Or "UNIX", in the authors' words, "A weak pun on Multics") Plural "Unices". An interactive time-sharing operating system invented in 1969 by Ken Thompson after Bell Labs left the Multics project, originally so he could play games on his scavenged PDP-7. Dennis Ritchie, the inventor of C, is considered a co-author of the system.

The turning point in Unix's history came when it was reimplemented almost entirely in C during 1972 - 1974, making it the first source-portable OS. Unix subsequently underwent mutations and expansions at the hands of many different people, resulting in a uniquely flexible and developer-friendly environment.

By 1991, Unix had become the most widely used multi-user general-purpose operating system in the world. Many people consider this the most important victory yet of hackerdom over industry opposition (but see Unix weenie and Unix conspiracy for an opposing point of view).

Unix is now offered by many manufacturers and is the subject of an international standardisation effort [called?]. Unix-like operating systems include AIX, A/UX, BSD, Debian, FreeBSD, GNU, HP-UX, Linux, NetBSD, NEXTSTEP, OpenBSD, OPENSTEP, OSF, POSIX, RISCiX, Solaris, SunOS, System V, Ultrix, USG Unix, Version 7, Xenix.

"Unix" or "UNIX"? Both seem roughly equally popular, perhaps with a historical bias toward the latter. "UNIX" is a registered trademark of The Open Group, however, since it is a name and not an acronym, "Unix" has been adopted in this dictionary except where a larger name includes it in upper case. Since the OS is case-sensitive and exists in many different versions, it is fitting that its name should reflect this.

The UNIX Reference Desk.

Spanish fire extinguisher.

Last updated: 2001-05-14

Unix box

box

Unix brain damage

Something that has to be done to break a network program (typically a mailer) on a non-Unix system so that it will interoperate with Unix systems. The hack may qualify as "Unix brain damage" if the program conforms to published standards and the Unix program in question does not. Unix brain damage happens because it is much easier for other (minority) systems to change their ways to match non-conforming behaviour than it is to change all the hundreds of thousands of Unix systems out there.

An example of Unix brain damage is a kluge in a mail server to recognise bare line feed (the Unix newline) as an equivalent form to the Internet standard newline, which is a carriage return followed by a line feed. Such things can make even a hardened jock weep.

Unix conspiracy

[ITS] According to a conspiracy theory long popular among ITS and TOPS-20 fans, Unix's growth is the result of a plot, hatched during the 1970s at Bell Labs, whose intent was to hobble AT&T's competitors by making them dependent upon a system whose future evolution was to be under AT&T's control. This would be accomplished by disseminating an operating system that is apparently inexpensive and easily portable, but also relatively unreliable and insecure (so as to require continuing upgrades from AT&T). This theory was lent a substantial impetus in 1984 by the paper referenced in the back door entry.

In this view, Unix was designed to be one of the first computer viruses (see virus) - but a virus spread to computers indirectly by people and market forces, rather than directly through disks and networks. Adherents of this "Unix virus" theory like to cite the fact that the well-known quotation "Unix is snake oil" was uttered by DEC president Kenneth Olsen shortly before DEC began actively promoting its own family of Unix workstations. (Olsen now claims to have been misquoted.)

Unix International

<body>

(UI) A consortium including Sun, AT&T and others formed to promote an open environment based on Unix System V, including the Open Look windowing system.

Unixism

<operating system, jargon>

A piece of code or a coding technique that depends on the protected multitasking environment with relatively low process-spawn overhead that exists on virtual-memory Unix systems.

Common Unixisms include: gratuitous use of "fork"; the assumption that certain undocumented but well-known features of Unix libraries such as "stdio" are supported elsewhere; reliance on obscure side-effects of system calls (use of "sleep" with a 0 argument to tell the scheduler that you're willing to give up your time-slice, for example); the assumption that freshly allocated memory is zeroed; and the assumption that fragmentation problems won't arise from never freeing memory.

Compare vaxocentrism. See also New Jersey.

Last updated: 1995-02-27

Unix man page

Unix manual page

(Or "man page") A part of Unix's extensive on-line documentation. To read a manual page from the Unix command line, type:

 man [-s<section>] <page>

e.g. "man ftp" (the section number can usually be omitted). Pages are traditionally referred to using the notation "page(section)", e.g. ftp(1).

Under SunOS (which is fairly typical), Section 1 covers commands, 2 system calls, 3 C library routines, 4 devices and networks, 5 file formats, 6 games and demos, 7 miscellaneous, 8 system administration. Each section has an introduction which can be obtained with, e.g., "man 2 intro".

Manual pages are stored as nroff source files. Formatted versions are also usually cached. Man pages for most versions of Unix are available on-line in HTML.

Unix manual page: man(1).

Linux man pages.

Solaris man pages.

Last updated: 2010-01-19

Unix System V

System V

Unix to Unix Copy

<networking, messaging>

(uucp) A Unix utility program and protocol that allows one Unix system to send files to another via a serial line which may be a cable going directly from one machine's serial port to another's or may involve a modem at each end of a telephone line.

Software is also available to allow uucp to work over Ethernet though there are better alternatives in this case, e.g. FTP or rcp for file transfer, SMTP for electronic mail or NNTP for news.

The term is now also used to describe the large international network which uses UUCP to pass Usenet news and electronic mail, also known as "UUCPNET".

Unix manual page: uucp(1).

UnixWare

Novell's implementation of Unix System 5 heavily based on Release 4.2 but with enhancements and new bundled products.

In 1993 Novell acquired Unix Systems Laboratories from AT&T along with the Unix trademark. UnixWare was the result of Novell's efforts to make Unix interoperable with Novell NetWare.

In 1995 Novell sold UnixWare and the rights to the Unix operating system to SCO at a time when UnixWare was gainnig popularity. It was later the first 64-bit operating system on the Intel platform, and, in 1999, is the world's fastest-growing commercial operating system.

[Any connection with X/Open? URL?]

Last updated: 1999-11-10

Unix weenie

<jargon>

(ITS) 1. A derogatory play on "Unix wizard", common among hackers who use Unix by necessity but would prefer alternatives. The implication is that although the person in question may consider mastery of Unix arcana to be a wizardly skill, the only real skill involved is the ability to tolerate (and the bad taste to wallow in) the incoherence and needless complexity that is alleged to infest many Unix programs. "This shell script tries to parse its arguments in 69 bletcherous ways. It must have been written by a real Unix weenie."

2. A derogatory term for anyone who engages in uncritical praise of Unix. Often appearing in the context "stupid Unix weenie".

See Weenix, Unix conspiracy, weenie.

Last updated: 1995-02-27

Unix wizard

<job>

Someone with a deep understanding of Unix.

See wizard.

Last updated: 1995-05-11

Unlicense

<legal>

A template for dedicating software to the public domain. It combines a copyright waiver like that of the SQLite project with the no-warranty statement from the MIT/X11 license.

http://unlicense.org/.

Last updated: 2014-07-31

unnormalised

normalisation

unproto

A translator from ANSI C to K&R C by Wietse Venema <[email protected]>.

ftp://ftp.win.tue.nl/pub/Unix/unproto4.shar.Z.

unshar

A Unix utility that removes e-mail and news header lines from its input, and feeds the remainder (which is presumed to be a shar file) to /bin/sh to unpack it. unshar is designed for unpacking archives directly from the news or mail systems simply by piping a message into it.

unshielded twisted pair

<hardware>

(UTP) Normal telephone wire (in the USA). It may be used for computer to computer communications, e.g. using a version of Ethernet or localtalk. It is much cheaper than standard "full-spec" Ethernet cable. It comes in five "catagories":

 cat.   wires   transmission
 1	two	voice no data (telephone cable)
 2	four 	data up to 4 Mbps
 3	four	data up to 10 Mbps
 4	four	data up to 16 Mbps
 5	four	data up to 100 Mbps

Last updated: 2003-07-04

unstable

<mathematics>

A description of an algorithm for which a small change or error in the initial values results in a large difference in the final result.

A description of a piece of software or hardware that is unreliable or prone to crash or is over-sensitive to its input or behaves in some other unpredictable way.

Last updated: 2019-12-27

unswizzle

The opposite of swizzle.

Last updated: 1995-02-15

until

while loop

untyped

A variable which can hold values of any type or a programming language in which some or all variables are like this.

An example would be VBScript, or Visual Basic's variant type.

Last updated: 2003-12-22

unwind-protect

(MIT) A Lisp operator which evaluates an expression and then, even if that expression causes a non-local exit, evaluates zero or more other expressions. This can be used to ensure that essential "clean-up" operations are performed even in the presence of errors.

Last updated: 1994-11-03

unwind the stack

During the execution of a procedural language, one is said to "unwind the stack" from a called procedure up to a caller when one discards the stack frame and any number of frames above it, popping back up to the level of the given caller. In C this is done with "longjmp"/"setjmp", in Lisp with "throw/catch". See also smash the stack.