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 shrink-wrapped 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.

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.

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 "lights-out operation."

UNI (User-Network Interface)
An asynchronous transfer mode (ATM) interface specification, defined by the ATM Forum. See ATM.

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."

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.

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-friendly
Any system, software or device that is easy to learn and use. Graphical user interfaces, for example, are designed to be user-friendly.

username
The unique identifier for each user on a network.

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.