U

U (see rack unit)

UA (Upgrade Advantage)

A Microsoft software license program.

UART (universal asynchronous receiver/transmitter)

An integrated circuit attached to the parallel bus in a computer that conducts serial

communications efficiently.

UBR (unspecified bit rate)

An asynchronous transfer mode (ATM) service category, defined by the ATM Forum,

that provides no service guarantees and therefore is a "best effort" service

equivalent to a shared-media LAN.

UCC (Uniform Code Council)

The U.S.-based, not-for-profit membership organization, founded in 1972, that

administers the EAN-UCC retail bar code system together with EAN International (its

European counterpart, founded in 1974). Through its UCCnet subsidiary, UCC is

currently focused on developing standards and specifications for an integration

marketplace for a range of industries. See EAN and UCCnet.

UCCnet

A subsidiary of the Uniform Code Council focused on developing an integration

marketplace for some two dozen industries. Its initial focus is on item

synchronization standards in grocery and apparel markets. Some 75 companies

(primarily consumer product and retail companies in North America ) subscribe to its

services, while more than 100 others are working on the development of the

integration marketplace through contributions to UCCnet Implementation Action

Groups (monthly sessions to develop the standards).

UCITA (Uniform Computer Information Transactions Act)

An act passed by the U.S. National Conference of Commissioners on Uniform State

Laws (NCCUSL) in 1999 and since enacted by some U.S. states (including Virginia

and Maryland ). UCITA ensures that software is treated not as goods, but rather as a

"computer information transaction," thereby exempting it from relevant consumer

product liability laws and requirements. UCITA further upholds the legality of shrinkwrapped

contracts and allows wide exemptions from liability and other "unfriendly"

contract items. However, consumers have some protections with UCITA, and in

2002, NCCUSL made some amendments to UCITA regarding warranties for

consumers.

UDB (Universal Database)

A IBM brand name applied to several of its DB2 database management system

products (for example, DB2 UDB for S/390, and DB2 UDB for Unix and Windows).

UDDI (Universal Description, Discovery and Integration)

A specification introduced by Microsoft, IBM and Ariba in 2000. It provides a

directory service for enterprises to publish, search for and use Web services. UDDI

specifies a standard format with which enterprises can describe themselves, and

their method of conducting e-business transactions, within an Internet-based

business registry. See Web services.

UDP (User Datagram Protocol)

A Transmission Control Protocol/Internet Protocol (TCP/IP) technology that enables

an application to send a message to one of several applications running in a

destination machine. UDP is stateless — it differentiates sources and destinations

within hosts and provides no other services. Often services do not use predefined

port numbers, so filtering on the basis of "well-known ports" will not work. See

TCP/IP.

UHF (ultrahigh frequency)

The range of radio frequencies between 300 and 3,000 megahertz.

UHID (Universal Healthcare Identifier)

A national healthcare identifier (NHID) format proposed by the American Society for

Testing and Materials' (ASTM's) Committee on Healthcare Informatics. The UHID is a

variable-length, numeric identifier that would include check digits and multiple

encryption capabilities. The perceived advantages of the UHID approach include

more reliable identification, improved functionality and more robust security

capabilities due to the unique design of the identifier. See ASTM and NHID.

UI (user interface)

The connection between the user and a computer's hardware or software that

permits the user to work productively with a system or a program. User interface

design requires significant skill and attention and has become a recognized specialty.

ultrahigh frequency (see UHF)

ultraportable

A computer system that meets all the criteria for a notebook PC but is lighter and

may not have an internal floppy disk drive. It typically weighs 4 pounds or less with

the battery and weight-saver modules. The keyboard and screen are often

compromised to meet weight targets and the unit must be augmented with a

standard keyboard and mouse for long-term use.

UltraSCSI

A high-speed version of the Small Computer System Interface (SCSI) bus. It

supports 40-megabyte-per-second transfers.

ultrawideband (see UWB)

Ultrix

A version of Unix from Compaq (formerly Digital Equipment), now merged with

Hewlett-Packard.

UM (unified messaging)

The convergence of a variety of communications media (e.g., e-mail, fax and voice)

into a single queue of messages, providing senders and recipients the freedom to

choose media and access devices.

UML (Unified Modeling Language)

A language for specifying, visualizing, constructing and documenting the artifacts of

software systems.

UMLS (Unified Medical Language System)

A system, maintained by the U.S. National Library of Medicine, that attempts to link

various controlled medical vocabularies (CMVs) using semantic relationships. See

CMV.

UMTS (Universal Mobile Telecommunications System)

The first of the third-generation (3G) cellular networks, UMTS is being designed to

offer speeds of at least 144 Kbps to fast-moving (e.g., vehicle-based) mobile

devices, and offer an initial 2 Mbps to campus sites — designers expect to increase

this to 10 Mbps by 2005. See 3G.

unattended operation

Operation of a communications or data-processing system transmission that is

controlled automatically and does not require a human operator. Also called "lightsout

operation."

UNI (User-Network Interface)

An asynchronous transfer mode (ATM) interface specification, defined by the ATM

Forum. See ATM.

Unified Medical Language System (see UMLS)

unified messaging (see UM)

Unified Modeling Language (see UML)

Uniform Code Council (see UCC)

Uniform Computer Information Transactions Act (see UCITA)

uniform resource locator (see URL)

uninterruptible power supply (see UPS)

universal asynchronous receiver/transmitter (see UART)

Universal Database (see UDB)

Universal Description, Discovery and Integration (see UDDI)

Universal Healthcare Identifier (see UHID)

Universal Mobile Telecommunications System (see UMTS)

universal queue

A process (and technology) whereby all contact channels and media — such as

phone, interactive voice response, fax, Web and e-mail — are integrated into the

same queue to standardize processing and handling. Also known as "universal

queuing."

Universal Serial Bus (see USB)

universal subscriber identity module (see USIM)

Unix

An operating system originally designed by Bell Laboratories in 1969. Since that

time, Unix has undergone a multitude of upgrades and enhancements, and has

proven to be adaptable to a variety of platforms. It has become a leading operating

system for servers and high-end workstations because of its scalability and support

of complex processing.

Unix-to-Unix Copy Program (see UUCP)

unshielded twisted pair (see UTP)

unspecified bit rate (see UBR)

uplink

The portion of a satellite circuit extending from an earth station to the satellite. See

downlink.

UPS (uninterruptible power supply)

A device that provides temporary power upon failure of the main power source.

UPU (universal power unit)

A metric once used by Oracle to license a number of its products. In June 2001,

Oracle eliminated its UPU-based license model and replaced it with processor-based

pricing.

URL (uniform resource locator)

The character string that identifies an Internet document's exact name and location.

USB (Universal Serial Bus)

A standard desktop input/output (I/O) bus that provides a single peripheral

connection and vastly increases bus speed. It simplifies peripheral connections via a

"daisy chaining" scheme whereby the desktop system has only one I/O port to which

all peripherals are connected in a series. Up to 120 peripherals can be connected to a

single system.

Usenet

Usenet — also known as "Netnews" — is a part of the Internet that is made up of

discussion forums or "newsgroups." The hierarchy is divided into seven high-level

categories — e.g., computing (comp), recreational (rec) and alternative (alt) —

which are in turn divided into numerous subgroups.

user

An individual who interacts with a computing device through applications. Technical

personnel are not considered to be users when they are programming or operating

the computer.

User Datagram Protocol (see UDP)

user-friendly

Any system, software or device that is easy to learn and use. Graphical user

interfaces, for example, are designed to be user-friendly.

user interface (see UI)

username

The unique identifier for each user on a network.

User-Network Interface (see UNI)

USIM (universal subscriber identity module)

An enhancement of the subscriber identity module (SIM) card used in Global System

for Mobile Communications (GSM) networks. The USIM is designed to be used in

third-generation (3G) networks. It is inserted into a 3G-compliant mobile phone to

provide network authentication and additional functions. See SIM, smart card and

3G.

USLI (ultra-large-scale integration)

More than 1 million transistors in a chip.

USS (Unix System Services)

A feature that provides Unix support under IBM's Multiple Virtual Storage (MVS) —

and, more recently, z/OS — operating-system environments. See MVS and z/OS.

UTP (unshielded twisted pair)

Wiring with one or more pairs of twisted insulated conductors housed in a single

plastic sheath. The wires are twisted around each other to minimize interference

from other twisted pairs in a cable bundle. UTP has no coaxial shielding.

UUCP (Unix-to-Unix Copy Program)

A protocol used for communication between geographically dispersed Unix systems.

UWB (ultrawideband)

Also known as "pulse radio," an emerging wireless technology that uses pulsed radio

techniques to transmit data. The transmitter sends a low-power broadband signal,

with each channel from 10 to 40 million pulses per second. The correlator, which

knows the timing code of the transmitter, listens at these intervals and decodes the

signal. Time Domain's Larry Fullerton invented the concept. Time Domain's impulse

transmitters emit ultra-short Gaussian monocyle pulses with pulse widths of between

1.5 nanoseconds and 2.0 nanoseconds. UWB also has applications in radar systems,

including systems that can detect people through walls or rubble.