- PC - Buzz - 1 A B C D E F G H I J K L M N O P Q R S T U V W X Y Z *

V.

Standarder for (modem-)datatransmission

CCITT (ITU) standarder:

14		i alle V.32 modemer
17		14400 bps fax
21		300 bps = Bell 103
22		1200 bps = Bell 212A
22bis		2400 bps
32		9600 bps
32bis		14400 bps
34		28800 bps ( blev under udviklingen kaldt V.Fast) - kræver 16550 UART
42		fejlkorrektion. Indeholder LAP-M og MNP 2-4
42bis		datakompression.

 

V.42

ITU-TSS standard for modem error checking that uses LAP-M as the promary protocol and provides MNP Classes 2 through 4 as an alternative protocol for compatibility.
The ITU's V.42 protocol is a highly standardized point-to-point error-checking protocol. It defines error-detection methods using LAP-M as the basic function (which is, itself, based on the Link Access Procedure/D-channel (LAPD) used in ISDN, which was also based on HDLC). To be fully compliant with this standard, the modem must implement LAP-M and also some alternative protocols based on MNP Classes 2-4. The key-word here is 'fully' compliant -- modems can be 'compliant' without implementing everything. During the handshake negotiations, two V.42 modems should attempt to apply LAP-M, and if this fails they will fallback to the MNP-4 protocol.

 

V.42bis

V.42bis A standard for data compression selected by the CCITT for modems -- especially those using the V.42 LAP-M error-control standard. It is based on the Lemple-Ziv-Welsh (LZW) algorithms, and is stable enough to work with ISDN direct links.
In V.42bis modems, there are always two accepted data compression techniques; V.42bis itself and MNP Class 5. This came about because of a patent dispute. The V.42bis standard is better, with a theoretical capability of 4:1 compression on some files (but generally 2:1 or 3:1 on text), while MNP 5 is probably only half as good with the average text file. A V.42bis modem probably averages considerably less than 3:1 compression in normal English text, although spreadsheets, cartoon-like images and assembly language programs will certainly be this level.
ISDN terminal adaptors have still not incorporation V.42 compression, mainly because of the expense. Unisys own the patent on LZW compression and has a blanket deal for it to be used in modems, but not in ISDN adaptors.

 

V.110

An ITU standard (1984) that specifies how data terminal equipment (DTE) with asynchronous or synchronous serial interfaces can be supported on an ISDN network. It uses rate adaption, which involves a bit-by-bit alignment between the DTE and the ISDN B channel.

V.120

An ITU standard (1988) that specifies how DTEs with asynchronous or synchronous serial interfaces can be supported on an ISDN network using a protocol (similar to LAP-D) to encapsulate the data to be transmitted. It includes the capability of using statistical multiplexing to share a B channel connection between multiple DTEs.

An ITU standard for Rate Adaptation on ISDN, offering enhancements over the V.110 standard. This allows a terminal adapter (TA) to connect to a low speed device (50bps to 19.2Kbps), such as a PC COM port, and convert the data so it can be sent over a 64Kbps link. In addition, it uses a LAPD-like protocol on the "B" channel so it is possible to support a number of multiplexed low-speed devices over one channel.

An ITU standard for rate-adaptation which uses HDLC frames with 56kb/s links. Interframe flags are used to pad these out to the full 64kb/s. Only seven of the eight bits are used, with the last bit being always set to 1. This technique supports asynchronous, HDLC-framed synchronous, and bit-transparent synchronous. Error detection (and some correction) is provided. Some statistical multiplexing is also possible

V.120 allows for reliable transport of synchronous, asynchronous, or bit transparent data over ISDN bearer channels.

An International Telecommunications Union (ITU) 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.

This protocol allows ISDN modems to transfer files using familiar protocols such as X-, Y-, and Zmodem. V.120 can only make a connection on one of the two data-carrying channels at a time over ISDN, so it is limited to a maximum throughput of 64 kbps. It is mostly used to connect to ISDN-capable BBSs. Connecting to an Internet service provider over ISDN uses PPP or MPPP rather than V.120 to establish communications.

> MPPP, PPP, Xmodem, Ymodem, Zmodem

Configuring V.120 Access

OEM standarder:

32terbo AT&T 19200 bps - med 'SmartLink' modem. V.32Te: external. V.32Ti: internal
FastClass Rockwell 28800 bps = V.FC

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VANS = Value Added Network Services

VANS leverandørerne tilbyder netværksdrift, tilkoblingsmuligheder, konvertering, etc.
Som alternativ til VANS operatører er det også muligt at anvende en fast opkobling mellem parterne eller opkobling via Internet. Der foregår dog i modsætning til VANS leverandører ikke nogen sikkerhedskopiering, logning etc., hvis Internettet anvendes. Hovedårsagen til anvendelse af Internettet vil derfor være de økonomiske fordele, der er forbundet med dette. Idag er der kun få virksomheder, der anvender Internettet som kommunikationsmedie for EDI meddelser, men det vil højst sandsynligt stige med udbygningen af de services, der udbydes på Internettet.
VANS postkasse-service sikrer, at data som sendes til "postboksen" ene og alene kan tømmes af den modtager, som afsenderen på forhånd har defineret.
VANS-leverandør Leverandør af eksterne kommunikationstjenester. Eksempelvis etableres Statens E-post fysisk ved, at den enkelte institution tilkobler sit elektroniske postsystem til en af markedets V'er. Markedets V'er tilbyder opkobling efter bl.a. X.400-anbefalingerne samt konvertering mellem forskellige opkoblingsformer. Datacentralen er med SDN i dag leverandør til et stort antal statsinstitutioner koblet op med forskellige opkoblingsformer. Andre V'er på det danske marked er Datacom, som har etableret X.400-forbindelser til et stort antal udenlandske X.400-tjenester, samt danNet, Kommunedata, DKnet og LEC. V'ere tilbyder bl.a. støtte til den tekniske opsætning af e-postsystemer og eksterne e-postforbindelser
 

www.edison.dk/Pages/vans.htm

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VB = Visual Basic

[whatis]: Visual Basic is a programming environment from Microsoft in which a programmer uses a graphical user interface to choose and modify preselected chunks of code written in the BASIC programming language.
Since Visual Basic is easy to learn and fast to write code with, it's sometimes used to prototype an application that will later be written in a more difficult but efficient language. Visual Basic is also widely used to write working programs. Microsoft says that there are at least 3 million developers using Visual Basic.
> VBA, VBScript
 

www.vb-web-directory.com : Visual Basic Web Directory
www.emsps.com/oldtools/msvbv.htm : Visual Basic Version Information

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VBA = Visual Basic for Applications

[Techweb] A subset of Visual Basic that provides a common language for customizing Microsoft applications. VBA supports COM, which allows a VBA script to invoke internal functions within Excel, Word and other COM-based programs or to make use of stand-alone, external COM objects. VBA evolved into a common language to consolidate earlier macro and scripting languages. Since 1996, VBA has been licensed to third parties for use in non-Microsoft applications within the Windows environment. Microsoft encourages Windows developers to put VBA support in their software.
> BASIC, VB, VBScript

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VADSL = Very high speed Asymmetric DSL

 

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VBscript

A subset of VBA, optimized for web programming - the code is embedded in HTML documents.
The VBscript engine is the file VBSCRIPT.DLL, installed by Internet Explorer in \WINDOWS\SYSTEM.
Supported by IE 3.0- (not Netscape)
> BASIC, VB, WSH, ASP

[whatis]: VBScript is an interpreted script language from Microsoft that is a subset of its Visual Basic programming language. VBScript can be compared to other script languages designed for the Web, including:
    Netscape's JavaScript
    Sun Microsystem's Tcl
    The UNIX-derived Perl
    IBM's REXX
In general, script languages are easier and faster to code in than the more structured, compiled languages such as C and C++ and are ideal for smaller programs of limited capability or that can reuse and tie together existing compiled programs. VBScript is Microsoft's answer to Netscape's popular JavaScript. Both are designed to work with an interpreter that comes with a Web browser - that is, at the user or client end of the Web client/server session. VBScript is designed for use with Microsoft's Internet Explorer browser together with other programming that can be run at the client, including ActiveX controls, automation servers, and Java applets. Although Microsoft does support Netscape's JavaScript (it converts it into its own JScript), Netscape does not support VBScript. For this reason, VBScript is best used for intranet Web sites that use the Internet Explorer browser only.

www.microsoft.com/msdownload/vbscript/scripting.asp
msdn.microsoft.com/scripting/ VBScript
help.activeserverpages.com/iishelp/VBScript/htm/VBStoc.htm : VBScript Language Reference
www.outlook.useast.net/vbsdoc/vbsdoc/vbstoc.htm : Language Reference
www.netcoders.dk/docs/vbscript/vbstoc.htm

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VCR = Video Cassette Recorder

>SCART

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VDSL = Very high speed DSL

 

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VeriSign

www.verisign.com

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Veronica = Very Easy Rodent-Oriented Net-wide Index to Computerized Archives

søgning i Gopher-databaser (hele Gopherspace)
> Jughead

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VESA = Video Electronics Standards Association

En forening af video elektronik producenter, som fastsætter standarder for edb-skærme og skærmkort
>SuperVGA

 

VESA-BUS, VESA Lokalbus, VL-Bus

32-bit 40/66 MHz databus mellem processoren og skærmkortet, netværkskortet og harddisken - understøtter bus-mastering.
VL-bussen benyttes sammen med den almindelige ISA eller EISA bus på pc'er med Intel 486 cpu.
I Pentium pc'er benyttes PCI-bus

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VFAT = Virtual File Allocation Table

32-bit 'protected mode' file access. Compatible with FAT (FAT16).
Tillader lange sti- (260) og filnavne (255). Bruges af Windows 3.11 og Windows 95-.

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VGA = Video Graphics Array

Standard for edb-skærme og grafikort, introduceret i 1987 - 640*480 punkter med 16/256 farver

>CGA, EGA, SuperVGA

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VHF = Very High Frequency

- radio bølger
> UHF

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VIA = Vendors ISDN Association

> AO/DI

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VIM = Vendor Independent Messaging

Leverandøruafhængig standard for formidling af meddelelser fremmet af bl.a. Lotus, Novell, IBM, Apple, Borland.
> cc:Mail

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virus

Programkode, som kan reproducere sig selv. Koden tilføjes et andet program, som - når det startes - også afvikler virus-koden - som vedhæfter kopier af sig selv til andre programmer, som derved også bliver inficerede.
Virus-koden indeholder ofte også instruktioner, som først afvikles, når en bestemt tilstand indtræder - fx en bestemt dato. Koden kan så evt gøre en eller anden skade på brugerens system.
 
Der findes mere end 50.000 forskellige virus-typer, men de fleste er ikke i cirkulation. Der udvikles fortsat nye virustyper, som udgør en aktuel risiko. En liste med de aktuelle virustyper kan fx findes på:

vil.nai.com/VIL/newly-discovered-viruses.asp : McAfee : Newly Discovered Threats

En database med alle kendte virustyper kan findes på:

http://vil.nai.com/VIL/default.asp : McAfee : Virus Information Library

 

> ActiveX, bomb, CIH, trojan, VSUM, worm
> Antivirusprogram

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VL-Bus

>VESA Lokalbus

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VLSI = Very Large Scale Integration

> chip

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VM = Virtual Machine

Software that mimics the performance of a hardware device - such as a program that allows Intel-applications to be run on Motorola-systems.

= OS/VM

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VMS = Virtual Memory System

Operating system by DEC running on VAX mini computers

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VPN = Virtual Private Network

For secure (encrypted) remote access via Internet
Supported by Windows 98
ISP support is required

A system that permits networks to extend beyond a physical home networks while giving the appearance and functonality of being directly connected to a home network. VPNs use L2TP and L2F to extend the Layer 2 and higher parts of the network connection from the ISP to the home gateway. The specific term "VPDN" is being replaced by the more general term "VPN."

A network service offered by public carriers in which the customer is provided a network that in many ways appears as if it is a private network (customer-unique addressing, network management capabilities, dynamic reconfiguration, etc.) but which, in fact, is provided over the carrier's public network facilities.

Uses DUN, IPSec, L2TP, PPTP
> Extranet, tunneling

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VRAM = Video RAM

[webopedia] : VRAM is special-purpose memory used by video adapters. Unlike conventional RAM, VRAM can be accessed by two different devices simultaneously. This enables the RAMDAC to access the VRAM for screen updates at the same time that the video processor provides new data. VRAM yields better graphics performance but is more expensive than normal RAM.
>WRAM.

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VRM = Voltage Regulator Module

- on motherboard

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VRML = Virtual Reality Modelling Language

A language much like HTML for getting data on the Web. The 3D nature of VRML is where the two specs depart.
ASCII script language for encapsulation, delivery and playback of 3D graphics on the Internet

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VSUM = Virus Summary

The Virus Information Summary List, VSUM, represents the cumulative knowledge produced by an ongoing research effort in the detection, identification, and removal of MS-DOS viruses. It will help you understand what a specific virus does, how it activates, how it affects your system, and more important, how to get rid of it!
 

www.vsum.com

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VT = Virtual Terminal

- session protocol of TCP/IP

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VT-

Terminalemulering.
- 52 Benyttes ved TELNET
-100 Benyttes ved TELNET
-200

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VxD = Virtual anything Driver

- 32-bit protected mode low-level software component that manages a single resource (screen, serial port, ...) for possibly many concurrent threads.

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