Technical Corner > The PC Glossary - Definitions of Computer and Internet Terms

Computer Terms Beginning with "V"

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MysteRy:
Source : PC.net


VCI

Stands for "Virtual Channel Identifier." The VCI, used in conjunction with the VPI (virtual path indicator), indicates where an ATM cell is to travel over a network. ATM, or asynchronous transfer mode, is a method that many ISPs (Internet Service Providers) use to transfer data to client computers. Because ATM sends packets over fixed channels, the data is easier to track than information sent over the standard TCP/IP protocol.

The VCI within each ATM cell defines the fixed channel on which the packet of information should be sent. It is a 16-bit field, compared to the VPI, which is only 8 bits. Since this numerical tag specifies the virtual channel that each packet belongs to, it prevents interference with other data being sent across the network.

MysteRy:
VDU

Example: "A digital projector is often used as a VDU for PowerPoint presentations."

A VDU is a Visual Display Unit. It is another term for monitor or screen, but may also refer to a projector or other type of display. VDUs may be peripheral devices or may be integrated into a computer system. While early VDUs were mainly CRT displays, today most monitors are flat panel displays that use LCD or LED technology.

MysteRy:
Vector

Mathematically, a vector is a quantity, defined by both magnitude and direction. For example, a vector could be illustrated by an 1 inch arrow pointing at a 30 degree angle. Another vector may be 2.5 inches and point at a 160 degree angle. In the computer world, vectors are used to define paths in certain types of images, such as EPS files and Adobe Illustrator documents. These images are often called vector graphics since they are comprised of vectors, or paths, instead of dots. Vector graphics can be scaled larger or smaller without losing quality.

In computer science, a vector may refer to a type of one dimensional array. For example, a vector called "fibonacci" that stores the first six values of the Fibonacci sequence would be defined as follows:

fibonacci[0] = 0, fibonacci[1] = 1, fibonacci[2] = 1, fibonacci[3] = 2, fibonacci[4] = 3, fibonacci[5] = 5

Vectors are similar to arrays, but unlike arrays, vectors use their own memory management mechanisms. Arrays are restricted to the memory structure supplied by the programming language they are created in, typically called a stack. Vectors have a more dynamic structure, often referred to as a heap, which gives them greater flexibility in how they use memory. While an array uses a static amount of memory, the memory used by the vector can be increased or decreased as elements are added or removed from the vector.

MysteRy:
Vector Graphic

Unlike JPEGs, GIFs, and BMP images, vector graphics are not made up of a grid of pixels. Instead, vector graphics are comprised of paths, which are defined by a start and end point, along with other points, curves, and angles along the way. A path can be a line, a square, a triangle, or a curvy shape. These paths can be used to create simple drawings or complex diagrams. Paths are even used to define the characters of specific typefaces.

Because vector-based images are not made up of a specific number of dots, they can be scaled to a larger size and not lose any image quality. If you blow up a raster graphic, it will look blocky, or "pixelated." When you blow up a vector graphic, the edges of each object within the graphic stay smooth and clean. This makes vector graphics ideal for logos, which can be small enough to appear on a business card, but can also be scaled to fill a billboard. Common types of vector graphics include Adobe Illustrator, Macromedia Freehand, and EPS files. Many Flash animations also use vector graphics, since they scale better and typically take up less space than bitmap images.

MysteRy:
Veronica

The name actually stands for "Very Easy Rodent-Oriented Netwide Index to Computerized Archives." Pretty weird, I know. The "rodent" part of the acronym refers to how the Veronica utility allows you to search all of the world's gopher servers using keywords. (That's about 10 million items from over 6,000 gopher servers.) After searching for the terms, Veronica displays a list of gopher menus and articles containing the key words you searched for. The more recent versions of Veronica can also search certain Web pages, newsgroups, and FTP sites.

Unlike most search engines, Veronica searches for keywords only in gopher server menu titles, and doesn't look throught the entire text of documents. When searching with Veronica, you can use the logical operators AND, NOT, and OR to help narrow your search. Also, typing an asterisk (*) at the end of a word will match anything starting with that word. Sound familar to any Unix users?

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