Modem error checking standards set by the CCITT/ITU. See also ITU.
Standards for high-speed synchronous data exchange used by most routers and DSUs. See also ITU.
56 kb/s modem standards set by the ITU in February, 1998. It settles the competition between X2 by 3COM/US Robotics and K56flex by Rockwell Semiconductor since both will now conform to V.90. See also ITU.
validation rules
Rules that ensure the data entered is of the correct data type, format, size, range, etc.
The range from black to white, independent of color/hue. Adding tint (black) lightens the value and decreases saturation of the hue. Adding tone (black) darkens the value and also decreases saturation of the hue.
When choosing color combinations, the relative values of the colors is probably the most important factor. It often helps to judge the relative values by squinting or viewing the image in grayscale or using a piece of red cellophane.
Value Added Reseller
See VAR.
vampire tap
A clamp-like device that bites into a cable so as to connect to it without cutting or splicing.
Software and hardware that is announced and advertised but is not yet available, and, typically, never is.
Value Added Reseller. A company that gets hardware and software from the various OEMs for the purpose of customizing the equipment, and eventual marketing under the VAR's name.
A symbol or word representing information, eg a = 69, where a is the variable whose name or identifier is a, and 69 is the information, constant, or literal assigned to that variable. Variables are temporary storage space on your computer that can be manipulated and processed. Variables and their literals are also usually of a particular data  type, eg boolean, number, or string variables.
A general purpose data type that can hold almost any kind or size of data. In MS VisualBasic this is the default data type.
Virtual Address eXtension. DEC's line of minicomputers first introduced in 1977 along with its VMS OS. This OS peaked in the 1980s but still sells.
Visual Basic. Microsoft Visual Basic is an event-driven programming language derived from BASIC, a procedural programming language.
Visual Basic for Access. A smaller version of VB that comes with the MS Access RDBMS.
Visual Basic RUNtime. The collection of libraries which allow Visual Basic programs to function. VBRUN is often accessed by shareware.
A 32 bit driver for Windows 95 that can adjust the size of the disk cache depending on the available space and the need. See also Smartdrive.
Vector Markup Language
See VML.
Vector Objects
Graphics rendered in a format that connects points, eg PGML and VML, as opposed to specifying each pixel as is raster images. Vector objects are usually a mix geometric shapes, curves, lines, splines, etc., easily defined by equations. Vector images can be scaled to any size without losing quality. Common tools for making vectors include CorelDraw, Adobe's Illustrator and PageMaker, Deneba Canvas, Aldus Freehand, and QuarkXPress, and Macromedia's Flash (a web browser plugging).
A search engine for FTPs released by the University of Nevada in 1992.
version control software
See revision control.
Virtual File Allocation Table. The FAT for Win 3.x and 95. See FAT.
Video Graphics Array. A widely accepted standard for video cards and monitors. It has a resolution of up to 640 x 480 pixels. See also video standards.
Emacs and vi compete for the position of most common common text editor for UNIX. vi is a screen oriented text editor written by Bill Joy in 1976.
video adapter
See video card.
video card
Aka video adapter. A controller card that controls communication between the CPU and the monitor. See also my article on Video.
Video Graphics Array
See VGA.
video standards
Defines the allowable resolution and colors for a computer/monitor. The monitor must be able to receive the standard and the video card on the computer must be able to transmit the standard.
Standard Resolution Max Colors
(Monochrome Display Adapter) ca 1970s
80 characters x 25 lines 2^1 = 2
(Hercules Graphics Card) ca 1980s
720 x 530 2^1 = 2
(Color Graphics Adapter) ca 1981
160 x 200 2^4 = 16
640 x 200  
(Enhanced Graphics Adapter) ca 1984
640 x 350 16 out of 2^6 = 64
(Video Graphics Array)
320 x 200 2^8 = 256
640 x 480  
(Super VGA) - 8514/A ca 1987
640 x 480 2^16 = 65,536
800 x 600  
1024 x 768  
1280 x 1024  
(eXtended Graphics Array) ca 1990
800 x 600 2^24 = 16,777,216
1024 x 768  
1280 x 1024  
(Ultra Graphics Array) ca 1992
1600 x 1200  

 See also my article on Video.

Aka logical. To be in essence or effect, right there.
virtual circuit
A connection between devices that appears to be a direct circuit when it may actually circuitous or even packet switched. Virtual circuits are either permanent (PVC) or switched on and off as needed (SVC).
Virtual File Allocation Table
virtual machine
See VM.
virtual memory
Aka page file. A portion of storage memory utilized for processing memory or caching. It provides alternate memory addresses in groups called pages. These pages are converted to real memory address when the program is actually executed. This paging or swapping is much slower than using real processing memory. However it is great for freeing up real RAM.
Virtual Memory System
See VMS.
virtual path
The path relative to the current directory, eg in UNIX if you are in /usr/guest then a virtual path to the file in /usr/guest/poems/rose.txt would be /poems/rose.txt.
Video Random Access Memory
Malicious programs code that stealthily invades systems and create undesirable effects and often have some means of reproduction. There are four major categories of viruses:
  • Virus. An executable file: does undesirable stuff and replicates.
  • Worm. Does not infect other files: primarily replicates itself.
  • Trojan Horse. Disguised as an innocuous executable file: does undesirable stuff, and replicates.
  • Macro. Attached to innocuous files as macro code. Many programs, including Microsoft Office, utilize macro languages to enhance their documents and apps. Does undesirable stuff and replicates.
Virtual Private Network
See VPN.
Virtual Reality Modeling Language
Virtual Telecommunications Access Method
Visual Basic Runtime
VESA Local Bus. Introduced in 1992, it is a faster version of EISA expansion slots.
Virtual Machine. An application that manages the execution of bytecode programs. EG: The same Java compiled bytecode can be run on different operating systems since a JVM (Java virtual machine) has been written for different operating systems, hence WORA (write once, run anywhere). Most VMs have settings for JIT (just-in-time) compilation which which introduces another level of recompilation.
Vector Markup Language. A Macromedia proposed W3C standard for vector images for the Web, akin to Adobe's proposal, PGML.
Virtual Memory System. Aka Open VMS in its later incarnations. A multi-user, multi-tasking, virtual memory operating system that runs on DEC's VAX or Alpha processor workstations, servers, and minicomputers. VMS was introduced in 1977 along with VAX.
Voice Over IP. Enabling the transmission of real-time voice conversations over the Internet using IP (Internet Protocol).
volatile memory
See processing memory.
VOice data. A file that contains raw sound data and no information about the formatting of the file. See also my article on Sound.
VOlume piXEL. The smallest box-shaped part of a 3D image. A volume is sliced into cross sections and each slice is composed of pixels. The pixels within each slice is a voxel. The actual volume is based on the interpixel distance squared times the interslice distance.

Each voxel has information about its 3D position and volume. Each voxel also has other information, such as opacity. Voxels are used in 3-D X-Rays, CAT (Computed Axial Tomography) Scans, MRIs (Magnetic Resonance Imaging) and 3D computer games.
Virtual Private Network. Network access over the Internet or another network that provides security and features similar to connection to an actual LAN. This is typically implemented with encryption, IP address hiding, and tunnelling protocols like PPTP (Point-to-Point Tunneling Protocol). VPN software is typically found at a network's firewall.
Video Random Access Memory. Unlike DRAM, VRAM can be accessed by the video card and the CPU simultaneously. This make VRAM faster but more expensive than DRAM when used in video cards.
.wrl. Virtual Reality Modeling Language. A developing language that creates navigatable 3D worlds (hence .wrl) on the WWW via a VRML browser or Web browser with a VRML plug-in. The specifications for VRML 2.0 were finalized in 1996/08 as ISO/IEC 14772.

Virtual Storage Access Method. A legacy file management system for IBM mainframes, including OS/390, formerly known as MVS (Multiple Virtual Storage). VSAM creates an index for files in the order they are entered. VSAM can also access records according to a custom key, eg product ID. VSAM succeeded SAM and ISAM but VSAM itself is often replaced in mainframes by real RDBMSs such as DB2, Oracle, etc.

Virtual Telecommunications Access Method. A SNA protocol which oversees the operation of an SNA network.

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