MICROSOFT Computer Dictionary, Fifth Edition

Microsoft Computer Dictionary, Fifth Edition

n. The direction in which information is delivered from a client to a (Web) server. Compare downstream1.

upstream2

adj. 1. The location of a server in relation to another server. Compare downstream2 (definition 1). 2. The direction in which data moves from an individual computer to the remote network. With certain communications technologies, such as ADSL, cable modems, and high-speed 56-Kbps modems, data flows upstream more slowly than downstream. For example, a 56-Kbps modem can deliver data at a 56-Kbps maximum only downstream; upstream, it delivers data at either 28.8 or 33.6 Kbps. Compare downstream2 (definition 2).

uptime

n. The amount or percentage of time a computer system or associated hardware is functioning and available for use. Compare downtime.

upward-compatible

adj. Of, pertaining to, or characteristic of a computer product, especially software, designed to perform adequately with other products that are expected to become widely used in the foreseeable future. The use of standards and conventions makes upward compatibility easier to achieve.

urban legend

n. A widely distributed story that remains in circulation in spite of the fact that it is not true. Many urban legends have been floating around the Internet and other online services for years, including the request for cards for the sick boy in England (he’s long since recovered and grown up), the cookie or cake recipe that cost $250 (it’s a myth), and the Good Times or Penpal Greetings virus, which will infect your computer when you read an e-mail message (it does not exist). See also Good Times virus.

URC

n. See Uniform Resource Citation.

URI

n. See Uniform Resource Identifier.

URL

n. Acronym for Uniform Resource Locator. An address for a resource on the Internet. URLs are used by Web browsers to locate Internet resources. A URL specifies the protocol to be used in accessing the resource (such as http: for a World Wide Web page or ftp: for an FTP site), the name of the server on which the resource resides (such as //www.whitehouse.gov), and, optionally, the path to a resource (such as an HTML document or a file on that server). See also FTP1 (definition 1), HTML, HTTP, path (definition 1), server (definition 2), virtual path (definition 1), Web browser.

URN

n. See Uniform Resource Name.

usable

adj. Of, pertaining to, or characteristic of the ease and adaptability with which a product can be applied to the performance of the work for which it is designed. A high degree of usability implies ease of learning, flexibility, freedom from bugs, and good design that does not involve unnecessarily complicated procedures.

usage analysis

Microsoft Computer Dictionary, Fifth Edition

n. Data collected to evaluate how a Web site is being used, such as visitor user names, how often each page was visited, and the types of Web browsers used.

USB

n. Acronym for universal serial bus. A serial bus with a data transfer rate of 12 megabits per second (Mbps) for connecting peripherals to a microcomputer. USB can connect up to 127 peripherals, such as external CD-ROM drives, printers, modems, mice, and keyboards, to the system through a single, general-purpose port. This is accomplished by daisy chaining peripherals together. USB is designed to support the ability to automatically add and configure new devices and the ability to add such devices without having to shut down and restart the system (hot plugging). USB was developed by Intel, Compaq, DEC, IBM, Microsoft, NEC, and Northern Telecom. It competes with DEC’s ACCESS.bus for lower-speed applications. See also bus, daisy chain, hot plugging, input/output port, peripheral. Compare ACCESS.bus.

U.S. Department of Defense

n. The military branch of the United States government. The Department of Defense developed ARPANET, the origin of today’s Internet and MILNET, through its Advanced Research Projects Agency (ARPA). See also ARPANET, Internet, MILNET.

Usenet or UseNet or USENET

n. A worldwide network of UNIX systems that has a decentralized administration and is used as a bulletin board system by special-interest discussion groups. Usenet, which is considered part of the Internet (although Usenet predates it), is comprised of thousands of newsgroups, each devoted to a particular topic. Users can post messages and read messages from others in these newsgroups in a manner similar to users on dial-in BBSs. Usenet was originally implemented using UUCP (UNIX-to-UNIX Copy) software and telephone connections; that method remains important, although more modern methods, such as NNTP and network connections, are more commonly used. See also BBS (definition 1), newsgroup, newsreader, NNTP, UUCP.

Usenet User List

n. A list maintained by the Massachusetts Institute of Technology that contains the name and e- mail address of everyone who has posted to the Usenet. See also Usenet.

user account

n. On a secure or multiuser computer system, an established means for an individual to gain access to the system and its resources. Usually created by the system’s administrator, a user account consists of information about the user, such as password, rights, and permissions. See also group1, logon, user profile.

user agent

n. In the terminology established by the ISO/ OSI reference model for LANs (local area networks), a program that helps a client connect with a server. Acronym: UA. See also agent (definition 3), ISO/OSI reference model, LAN.

user control

n. In ASP.NET: A server control that is authored declaratively using the same syntax as an ASP.NET page and is saved as a text file with an .ascx extension. User controls allow page functionality to be partitioned and reused. Upon first request, the page framework parses a user control into a class that derives from System.Web.UI.UserControl and compiles that class into an assembly, which it reuses on subsequent requests. User controls are easy to develop due to their page-style authoring and deployment without prior compilation. In Windows Forms: A composite control that provides consistent behavior and user interface within or across applications. The user control can be local to one application or added to a library and compiled into a DLL for use by multiple applications.

User Datagram Protocol

Microsoft Computer Dictionary, Fifth Edition

n. See UDP.

user-defined data type

n. A data type defined in a program. User-defined data types are usually combinations of data types defined by the programming language being used and are often used to create data structures. See also data structure, data type.

user-defined function key

n. See keyboard enhancer, programmable function key.

user-friendly

adj. Easy to learn and easy to use.

user group

n. A group of people drawn together by interest in the same computer system or software. User groups, some of which are large and influential organizations, provide support for newcomers and a forum where members can exchange ideas and information.

user-initiated update

n. An operating system update mechanism, provided by the dial-up boot loader, which is designed to be used by remote users and field technicians. The operating system image is downloaded using a modem connection. See also automatic update, factory update.

user interface

n. The portion of a program with which a user interacts. Types of user interfaces, or UIs, include command-line interfaces, menu-driven interfaces, and graphical user interfaces. Acronym: UI.

User Interface Toolbox n. See Toolbox.

username

n. The name by which a user is identified to a computer system or network. During the logon process, the user must enter the username and the correct password. If the system or network is connected to the Internet, the username generally corresponds to the leftmost part of the user’s e-mail address (the portion preceding the @ sign, as in username@company.com). See also e- mail address, logon.

user name

n. The name by which a person is known and addressed on a communications network. See also alias (definition 2).

user profile

n. A computer-based record maintained about an authorized user of a multiuser computer system. A user profile is needed for security and other reasons; it can contain such information as the person’s access restrictions, mailbox location, type of terminal, and so on. See also user account.

user state

n. The least privileged of the modes in which a Motorola 680x0 microprocessor can operate. This is the mode in which application programs are run. See also 68000. Compare supervisor state.

USnail

n. 1. Slang for the United States Postal Service. USnail, a term used on the Internet, is a reference to how slow the postal service is in comparison to e-mail. 2. Mail delivered by the United States Postal Service. See also snail mail.

Microsoft Computer Dictionary, Fifth Edition

/usr

n. A directory in a computer system that contains subdirectories owned or maintained by individual users of the computer system. These subdirectories can contain files and additional subdirectories. Typically, /usr directories are used in UNIX systems and can be found on many FTP sites. See also FTP site.

USRT

n. Acronym for universal synchronous receiver-transmitter. A module, usually composed of a single integrated circuit, that contains both the receiving and transmitting circuits required for synchronous serial communication. Compare UART.

UTC

n. See Universal Time Coordinate.

UTF-8

n. Acronym for UCS Transformation Format 8. A character set for protocols evolving beyond the use of ASCII. The UTF-8 protocol provides for support of extended ASCII characters and translation of UCS-2, an international 16-bit Unicode character set. UTF-8 enables a far greater range of names than can be achieved using ASCII or extended ASCII encoding for character data. See also ASCII, Unicode.

utility

n. A program designed to perform a particular function; the term usually refers to software that solves narrowly focused problems or those related to computer system management. See also application.

utility program

n. A program designed to perform maintenance work on the system or on system components (for example, a storage backup program, disk and file recovery program, or resource editor).

UTP

n. Acronym for unshielded twisted pair. A cable containing one or more twisted pairs of wires without additional shielding. UTP is more flexible and takes up less space than shielded twistedpair (STP) cable but has less bandwidth. See the illustration. See also twisted-pair cable. Compare STP.

Microsoft Computer Dictionary, Fifth Edition

UTP.

.uu

n. The file extension for a binary file that has been translated into ASCII format using uuencode. Also called: .uud. See also ASCII, binary file, uuencode1. Compare .uue.

UUCP

n. Acronym for UNIX-to-UNIX Copy. A set of software programs that facilitates transmission of information between UNIX systems using serial data connections, primarily the public switched telephone network. See also uupc.

.uud

n. See .uu.

uudecode1

n. A UNIX program that converts a uuencoded file back into its original binary format. This program (along with uuencode) allows binary data, such as images or executable code, to be disseminated through e-mail or newsgroups. Compare uuencode1.

uudecode2

vb. To transform a uuencoded file back into its binary original using the uudecode program. Compare uuencode2.

.uue

n. The file extension for a file that has been decoded from ASCII format back into binary format using uudecode. See also ASCII, binary file, uudecode1.

uuencode1

n. A UNIX program that converts a binary file, in which all 8 bits of every byte are significant, into printable 7-bit ASCII characters without loss of information. This program (along with uudecode) allows binary data, such as images or executable code, to be disseminated through e-mail or newsgroups. A file thus encoded is one-third again as long as the original. Compare uudecode1.

uuencode2

Microsoft Computer Dictionary, Fifth Edition

vb. To transform a binary file into printable 7-bit ASCII text using the uuencode program. Compare uudecode2.

UUID

n. Acronym for universally unique identifier. A 128-bit value that uniquely identifies objects such as OLE servers, interfaces, manager entry-point vectors, and client objects. Universally unique identifiers are used in cross-process communication, such as remote procedure calling (RPC) and OLE. Also called: GUID.

uupc

n. The version of UUCP for IBM PCs and PC-compatibles running DOS, Windows, or OS/2. This version is a collection of programs for copying files to, logging in to, and running programs on remote networked computers. See also UUCP.

V: V.120 - VxD

V.120

n. The ITU-T (formerly CCITT) standard that governs serial communications over ISDN lines. Data is encapsulated using a protocol similar to the Lightweight Directory Access Protocol (LDAP), and more than one connection may be multiplexed on a communications channel. See also communications channel, communications protocol, International Telecommunications Union, ISDN, Lightweight Directory Access Protocol, multiplexing, standard (definition 1), V series.

V20, V30

n. NEC microprocessors that were slight improvements on Intel’s 8088 and 8086, using the same command sets but different microcode.

V.2x, V.3x, V.4x, V.5x series n. See V series.

V.32terbo

n. A modem protocol developed by AT&T for 19,200-bps modems, with fallback to the speeds supported by the ITU-T (formerly CCITT) V.32 standard. This protocol is proprietary to AT&T and was not adopted by CCITT or ITU-T. In the V series, V.34 takes the place of V.32terbo. See also International Telecommunications Union, V series.

V.34

n. Data transmission standard that provides for up to 28,800 bits per second (bps) communications over telephone lines. It defines a full-duplex (two-way) modulation technique and includes error-correcting and negotiation. See also bits per second, full-duplex, modulation standards, V.90.

V.42

n. The ITU-T (formerly CCITT) recommendation specifying procedures for error correction in data communications equipment (DCEs) designed for asynchronous-to-synchronous conversion. See also V series.

V.42bis

n. The ITU-T (formerly CCITT) recommendation specifying procedures for data compression in data-circuit terminating equipment utilizing error-correction operations. See also V series.

V86 mode

n. See virtual real mode.

Microsoft Computer Dictionary, Fifth Edition

V.90

n. Data transmission standard that provides for up to 56,000 bits per second (bps) communications over telephone lines. The transmission speed from the client-side modem for uploads is 33,600 bps. The transmission speed for downloads from the host-side modem such as an Internet service provider (ISP) or a corporate network is up to 56,000 bps, with an average speed of 40,000 to 50,000 bps. When the host-side modem does not support this standard, the alternative is V.34. See also bits per second, client, host, ISP, modem, modulation standards, V.34.

VAB

n. See voice answer back.

VAC

n. See volts alternating current.

vacuum tube

n. A set of metal electrodes and intervening metal grids, contained in a glass or metal tube from which all gas has been removed. Voltages on the grids control electrical currents between the electrodes. Formerly used for amplification and switching in electronic circuits, vacuum tubes are now used in applications such as cathode-ray tubes and those requiring very high power levels. A vacuum tube is known as a valve in Great Britain.

validation server controls

n. A set of server controls, included with ASP.NET, that verify user input. The input is checked as it comes from HTML server controls and Web server controls (for example, a Web page form) against programmer-defined requirements. Validation controls perform input checking in server code. If the user is working with a browser that supports DHTML, the validation controls can also perform validation using client script. See also ASP.NET server control, HTML server control, Web server control.

validation suite

n. A set of tests that measures compliance with a standard, especially a standard definition of a programming language. See also standard (definition 1).

valid date interval

n. A span of time during which a computer will maintain the correct date. For many PCs, the valid date interval is 1980 forward.

validity check

n. The process of analyzing data to determine whether it conforms to predetermined completeness and consistency parameters.

value

n. A quantity assigned to an element such as a variable, symbol, or label. See tone (definition 1).

value-added network

n. A communications network that offers additional services, such as message routing, resource management, and conversion facilities, for computers communicating at different speeds or using different protocols. Acronym: VAN.

value-added reseller

n. A company that buys hardware and software and resells it to the public with added services, such as user support. Acronym: VAR.

value list

Microsoft Computer Dictionary, Fifth Edition

n. A list of values used by some application, such as a database, as a search string or as values for a filtered query. See also filter (definition 1), query (definition 1), search string.

value type

n. A data type that is represented by the type’s actual value. If a value type is assigned to a variable, that variable is given a fresh copy of the value. (This is in contrast to a reference type, where assignment does not create a copy.) Value types are usually created on a method’s stack frame, rather than in the garbage-collected heap. A value type can be boxed, which is a process that creates a corresponding reference type. See also reference type.

valve

n. See electron tube, vacuum tube.

vampire tap

n. A type of transceiver used on Ethernet networks that is equipped with sharp metal prongs that pierce the insulation on thicknet cable to make contact with the copper core over which signals travel.

VAN

n. See value-added network.

vanilla

adj. See plain vanilla.

vaporware

n. Software that has been announced but not released to customers. The term implies sarcastically that the product exists only in the minds of the marketing department. Compare freeware, shareware.

VAR

n. See value-added reseller.

variable

n. In programming, a named storage location capable of containing data that can be modified during program execution. See also data structure, data type, global variable, local variable. Compare constant.

variable expression

n. An expression that depends on the value of at least one variable and, hence, must be evaluated during program execution. See also run time (definition 1), variable. Compare constant expression.

variable-length field

n. In a record, a field that can vary in length according to how much data it contains. See also field (definition 1).

variable-length record

n. A record that can vary in length because it contains variable-length fields, certain fields only under certain conditions, or both of these. See also variable-length field.

VAX

n. Acronym for virtual address extension. A family of 32-bit minicomputers introduced by Digital Equipment Corporation in 1978. The VAX, like the later 68000 microprocessor, has a flat address space and a large instruction set. The VAX was highly favored within the hacker community but has been superseded by microprocessors and RISC workstations. See also flat address space, instruction set, microprocessor, minicomputer, RISC.

Microsoft Computer Dictionary, Fifth Edition

VBA

n. See Visual Basic for Applications.

vBNS

n. Short for very high-speed Backbone Network Service. A network connecting several supercomputer centers and reserved for high-performance, high-bandwidth scientific applications requiring massive computing power. The vBNS was developed by the National Science Foundation and MCI Telecommunications. It began operation in 1995, reaching speeds of 2.4 Gbps, using MCI’s network of advanced switching and fiberoptic transmission technologies. Later, vBNS expanded to provide backbone services for Internet2.

VBScript

n. See Visual Basic, Scripting Edition.

VBS/VBSWG virus

n. Acronym for Visual Basic Script/ Visual Basic Script Worm Generator virus. Any virus created using the VBSWG virus creation toolkit. The tools available in VBSWG worm kit allow individuals to write viruses without having significant computer knowledge. Homepage and the Anna Kournikova virus are examples of VBS/VBSWG viruses.

VBX

n. Short for Visual Basic custom control. A software module that, when called by a Visual Basic application, produces a control that adds some desired feature to the application. A VBX is a separate executable file, usually written in C, that is dynamically linked to the application at run time and can be used by other applications, including some applications not developed in Visual Basic. Although VBX technology was developed by Microsoft, most VBXs have been written by third-party developers. VBXs are still in use, but the technology has been superseded by OCXs and ActiveX controls. See also control (definition 2), Visual Basic. Compare ActiveX controls, dynamic-link library, OCX.

VCACHE

n. The disk caching software used with VFAT driver in Windows 9x. VCACHE uses 32-bit code, runs in protected mode, and automatically allocates space in RAM rather than requiring the user to reserve space for the cache. See also cache, driver, protected mode, RAM, VFAT.

vCalendar

n. A specification defining the format for applications to exchange scheduling information. The vCalendar specification is based on existing industry standards, including international standards for representing dates and times, and permits the exchange of schedules and “to-do” lists of the sort users commonly enter into personal calendars. Like the companion vCard specification for electronic business cards, it was created by the versit consortium founded by Apple, AT&T, IBM, and Siemens. Handed off to the Internet Mail Consortium (IMC) in 1996, vCalendar is supported by numerous hardware and software vendors. See also vCard.

vCard

n. A specification for creating an electronic business card (or personal-information card) and for the card itself. Designed to be exchanged through applications such as e-mail and teleconferencing, a vCard includes information such as name, address, telephone and fax number(s), and e-mail address. It can also include time-zone, geographic location, and multimedia data such as photographs, company logos, and sound clips. Based on the ITU’s X.500 directory services specification, vCard was developed by versit, a consortium whose principal members include Apple, AT&T, IBM, and Siemens. The specification is under the guidance of the Internet Mail consortium Version 3.0 of the vCard specification has been approved as a proposed standard by the IETF. A companion specification known as vCalendar supports electronic exchange of scheduling information. See also vCalendar, X series.

Microsoft Computer Dictionary, Fifth Edition

V-chip

n. Electronic chip for installation in a television, VCR, cable box, or stand-alone device to provide adults with the ability to block programming they deem inappropriate. Intended to provide parents with a means of controlling the programming viewed by children, the V-chip allows adults to screen programs based on a rating level transmitted in the portion of the TV signal known as the vertical blanking interval (the same portion that carries closed captioning information). When programs exceed the chosen level, the V-chip signals the television, which then displays an “unauthorized to receive” message on a blank screen.

VCOMM

n. The communications device driver in Windows 9x that provides the interface between Windows-based applications and drivers on one side, and port drivers and modems on the other. See also driver.

VCPI

n. See Virtual Control Program Interface.

VCR-style mechanism

n. 1. A user interface for playing movie files that has controls similar to those on a videocassette recorder (VCR). 2. A type of motorized docking mechanism in which a laptop or notebook computer is physically locked into place by the docking station. The advantage to a VCR-style mechanism is that it provides an electrically consistent, secure bus connection. See also docking mechanism, docking station, laptop, portable computer.

VDD

n. Acronym for virtual display device driver. See virtual device driver.

VDL

n. Acronym for Vienna Definition Language. A metalanguage, containing both a syntactic and a semantic metalanguage, used to define other languages. See also metalanguage.

VDM

n. See video display metafile.

VDSL

n. Short for very-high-speed digital subscriber line. The high-speed version of the xDSL (digital subscriber line) communication technologies, all of which operate over existing phone lines. VDSL can deliver up to 52 Mbps downstream, but it is effective only within about 4500 to 5000 feet of the central exchange. The data delivery rate is, in fact, related to the distance the signal must travel. To attain a rate of 52 Mbps, for example, the subscriber must be within 1000 feet of the exchange office. At a distance of 3000 feet, the data rate drops to about 26 Mbps; and at 5000 feet, the data rate drops to about 13 Mbps. See also central office, xDSL.

VDT

n. Acronym for video display terminal. A terminal that includes a CRT (cathode-ray tube) and keyboard. See also CRT.

VDU

n. Acronym for video display unit. A computer monitor. See also monitor.

vector

n. 1. In mathematics and physics, a variable that has both distance and direction. Compare scalar. 2. In computer graphics, a line drawn in a certain direction from a starting point to an endpoint, both of whose locations are identified by the computer using x-y-coordinates on a grid. Vectors are used in the output of some graphics programs instead of groups of dots (on paper) or