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user agent.

universal asynchronous receiver-transmitter.

A connectionless communication protocol, that corresponds approximatively to transport layer protocols within the OSI reference model. UDP is the abbreviation for User Datagram Protocol.

In micrographics, microfiche with images reduced more than ninety times.

unary operation:
Synonym for monadic operation.

unary operator:
Synonym for monadic operator.

unavailable time:
From the point of view of a user, the time during which a functional unit cannot be used.

unbalanced merge sort:
A merge sort, which is an external sort, such that the sorted subsets created by the internal sorts are unequally distributed among some of the available external storage devices. The subsets are merged onto the remaining auxiliary storage devices and the process repeated until all items are in one sorted set.

The degree to which the validity of a fact or a rule in the knowledge base is in doubt.

unconditional branch:
Synonym for unconditional jump.

unconditional jump:
A jump that takes place whenever the instruction specifies it is executed. Synonymous with unconditional branch. Contrast with conditional jump.

unconditional jump instruction:
A jump instruction that specifies a mandatory jump.

unconditional statement:
A statement that is executed without any condition. Synonymous with imperative statement.

To restore text or graphics that were previously deleted, but whose changes have not been made permanent, such as by use of a save command.

In an operation, a result whose absolute value is too small to be represented within the range of the numeration system in use.

underflow exception:
An exception that occurs when the result of an operation causes an arithmetic underflow.

underflow indication:
An indication that an underflow occurred.

To print or display a horizontal line directly under a character, or under a group of characters. Synonymous with underscore.

underlying type:
Synonym for base type.

The sampling of a signal at a rate below that required by the Nyquist theorem. Undersampling results in a loss of resolution.

Synonym for underline.

A measure of the ease with which a person may read a program and of the ease of isolation of the data structures or data objects and algorithms in the solution that map to the real-world data and algorithms.

A function that enables a user to cancel the effects of the most recently executed command or commands. Some commands are irreversible.

An international standard for character encoding that supports 2-byte wide characters.

uniform referencing:
A property of a programming language such that two or more language constructs for referencing are of the same form; for example, language constructs for name qualification and indirect references; language constructs for subscripting and actual parameters.

unit separator character (US):
The information separator used as a delimiter between sequences of characters called units.

(1) A device that has a special function. (2) A basic element.

unit string:
A string that contains one element.

unit test:
A test of individual programs or modules in order to ensure that there are no analysis or programming errors.

universal asynchronous receiver-transmitter (UART):
A circuit used in asynchronous, synchronous, or combined synchronous and asynchronous data communication applications to provide all the necessary logic to receive data serial-in parallel-out and to transmit parallel-in serial-out; usually it transmits by means of duplex transmission, and can accommodate various word lengths.

Universal Personal Telecommunications (UPT):
A service that
  1. enables access to telecommunications services while accommodating personal mobility, and
  2. enables each user to participate in a user-defined set of subscriber services and to initiate and receive calls on the basis of a unique, personal, network-independent UPT Number across multiple networks at any terminal, fixed, movable, or mobile, regardless of geographic location.
Access to the service is limited only by terminal and network capabilities and restrictions imposed by the network provider. Contrast with personal communications services.

Universal Resource Locator (URL):
A universal naming convention that is used for locating and accessing resources via the Internet. The general form of a URL is as follows:
scheme://<user>:< password>@<host_name>:<port>/<path>/file
Some parts are not necessary in all cases.
<scheme> is the access protocol, e.g., http, ftp, etc.
<user>:< password> is not usually required.
<host_name> is a fully qualified domain name and is obligatory.
<path> indicates the access to a resource or to a document inside the host. If it is omitted, we get generally a default home page.
Examples of URL identifying an Internet site, or a file, or a service:
"http://www.iso.ch" is the URL of the site of the headquarters of the International Organization for Standardization "ISO". This site is located in Geneva, Switzerland ("ch" is the ISO Country Code of Switzerland).
"http://www.iso.ch/welcome.html" is the URL of the home page in English of the "ISO" site. This file is accessible by the HTTP protocol.

universal serial bus port:
Synonym for USB port.

universal set:
The set that includes all of the elements of concern in a given study.

universal Turing machine:
A Turing machine that can simulate any other Turing machine.

universal type:
The data type of numeric literals and the data type of the result of some predefined operations used for compliance with strong typing; for example: in Ada, a number declaration (without a data type) assumes a universal type.

universe of discourse:
In a particular context, all entities that are of interest. A universe of discourse may include many entity worlds, possibly including entities that are not yet perceived or considered; for example: if the area of interest is "finance," the universe of discourse could be "all financial aspects of an organization."

The adjustment of the knowledge stored in a system to remove learning.

To recover the original form of the data from packed data.

unpacked decimal notation:
A binary-coded decimal notation in which each decimal digit is represented in one byte.

unrecoverable error:
An error for which recovery is impossible without the use of recovery techniques external to the program.

unrestricted recognition system:
Synonym for speaker-independent system.

unstable state:
A state in which an entity remains for a finite period of time at the end of which it returns spontaneously to a stable state.

unstratified language:
A language that can be used as its own metalanguage; this concept encompasses most natural languages. Contrast with stratified language.

To delete one's address from a distribution list.

unsupervised learning:
A learning strategy that consists in observing and analyzing different entities and determining that some of their subsets can be grouped into certain classes, without any correctness test being performed on acquired knowledge through feedback from external knowledge sources. Once a concept is formed, it is given a name that may be used in subsequent learning of other concepts. Synonymous with learning without a teacher.

A language construct for iteration control that defines a test to be performed after each iteration step.

until statement:
An iteration statement where the iteration control is incorporated in an until-construct.

To state explicitly and in full, without the use of modifiers, all the instructions that are involved in the execution of a loop.

update dynamics:
The interaction of changes of shape, color, or other properties of the objects viewed in a display.

(1) In a local area network, pertaining to data transmission from a data station to the headend. (2) In satellite systems and airborne platforms, that portion of a communication link used for transmission of signals from a surface terminal to a satellite or airborne platform.

The transfer of programs or data to another computer. Originally the concept was to transfer data from a small computer to a larger one.

Universal Personal Telecommunications.

up time:
The time during which a functional unit is capable of performing a required function while the required external resources are provided, the unit is accessible to the user, and its constituent hardware, if any, is powered.

Universal Resource Locator, Uniform Resource Locator.

The unit separator character.

usability test:
A test to determine whether an implemented system fulfills its functional purpose as determined by its users. Synonymous with fitness-for-use test.

USB port:
A serial bus port with a bandwidth of 1.5 megabits per second for high-speed connection of peripheral equipment to microcomputers. USB can connect up to 127 peripherals to the system through a single, general purpose port, by daisychaining peripherals together. Synonymous with universal serial bus port.

A loosely connected set of computers and networks for creating, forwarding, or displaying computer conferences based on the concept of distributed bulletin board systems.

(1) A person, device, program, or computer system that uses a computer system for the purpose of data processing and information exchange. (2) In electronic mail, a person or a functional unit that participates in message handling as a potential source or destination.

user agent (UA):
In electronic mail, a functional unit by means of which a single direct user interacts with a message handling system. The user agent is a component of the message handling system by which the user creates, submits, or receives messages.

user class of service:
A category of data transmission service provided by a data network in which the data signaling rate, the data terminal equipment operating mode, and the code structure, if any, are standardized.

user coordinate:
A coordinate specified by a user and expressed in a device-independent coordinate system.

user data:
(1) The data recorded on a data medium for a user as contrasted with data controlling the processing of such data. (2) In electronic mail, in HTML, or in other application software, the information to be transmitted from one user to one or more other users. Contrast with header. (3) In OSI, data transferred between entities of a given layer on behalf of the entities of the next higher layer for which the former entities are providing services. (Figure 3 - Interconnection of data stations on a trunk cable).

user data area:
On an optical disk, a part of the information zone containing user data. Synonymous with data zone.

User Datagram Protocol:

user-defined link:
A hyperlink established under user control when using a hypermedia application.

user-defined path:
A hypermedia path defined by a user and stored by a hypermedia application for easy access in the future.

user facility:
In data communications, a set of functions available on demand to a user, and provided by a data network as a service for data transmission. Some facilities may be available on a per-call basis, and others may be assigned for an agreed period of time at the request of the user.

Pertaining to the ease and convenience of use by humans.

user ID:
A character string or pattern that is used by a data processing system to identify a user. Synonymous with user identification.

user identification:
Synonym for user ID.

user interface:
The part of a system with which a user interacts.

user manual:
A document that describes how to use a functional unit, and that may include description of the rights and responsibilities of the user, the owner, and the supplier of that functional unit. Synonymous with user's guide.

user profile:
(1) A description of a user, typically used for access control. A user profile may include data such as user ID, user name, password, access rights, and other attributes. (2) A pattern of a user's activity that can be used to detect changes in normal activity.

user's guide:
Synonym for user manual.

user terminal:
A terminal that enables a user to communicate with a computer.

user-tuned system:
Synonym for speaker-adaptive system.

user view:
The aspects of a universe of discourse that are of interest to a specific user or user group together with the relevant information, represented by a corresponding collection of data.

utility program:
A program that provides general, frequently needed services for computer users and service personnel; for example, a diagnostic program; a trace program; a sort program.

utility routine:
A routine that provides general, frequently needed services for computer users and service personnel; for example, an input routine.

utterance spectrogram:
Synonym for speech spectrogram.

A process for decoding UUencoded data.

A process for conveying binary data into a character string for use over a character-only channel. UUencoding was originally developed in the UNIX-to-UNIX environment.

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