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Glossary - I to Q

IP Number (Internet Protocol Number)

Sometimes called a dotted quad. A unique number consisting of 4 parts separated by dots. Every machine that is on the Internet has a unique IP number - if a machine does not have an IP number, it is not really on the Internet. Many machines (especially servers) also have one or more Domain Names that are easier for people to remember.

Java

Java is a network-friendly programming language invented by Sun Microsystems. It is often used to build large, complex systems that involve several different computers interacting across networks, for example transaction processing systems.

Java is also used to create software with graphical user interfaces such as editors, audio players, web browsers, etc. it is for creating programs that run in small electronic devicws, such as mobile telephones. Using small Java programs (called "Applets"), Web pages can include functions such as animations,calculators, and other fancy tricks.

JavaScript

JavaScript is a programming language that is mostly used in web pages, usually to add features that make the web page more interactive. When JavaScript is included in an HTML file it relies upon the browser to interpret the JavaScript. When JavaScript is combined with Cascading Style Sheets(CSS), and later versions of HTML (4.0 and later) the result is often called DHTML.

JPEG (Joint Photographic Experts Group)

JPEG is most commonly mentioned as a format for image files. JPEG format is preferred to the GIF format for photographic images as opposed to line art or simple logo art.

Meta Tag

A specific kind of HTML tag that contains information not normally displayed to the user. Meta tags contan information about the page itself, hence the name ("meta" means "about this subject").

Typical uses of Meta tags are to include information for search engines to help them better categorize a page.

MIDI (Musical Instrument Digital Interface)

Describes the physical connectors and the rules by which compatible computers and digital music synthesisers work together. Five-pin Din plugs and sockets are used to provide connections for digital data in, out and thru; the last outputs a copy of the incoming data to enable 'daisy chaining' of devices. Communication is in serial (one bit at a time) form at 31.25Kbit/sec.

MP3

An industry standard developed in 1992 by the German Frauenhofer Research Institute and achieves a spectacular compression ratio of a sampled audio wave - ranging from a factor of 8 to a factor of 12, depending upon the source. MP3 divides the frequency range into 32 bands, each of which the human ear hears separately. The component of the input signal in each band is then subjected to a Fourier-like mathematical transformation that separates it into a further 18 constituents generating a total of 576 individual frequency bands. Within these bands components undetectable to the human ear are thrown away. The resulting signal is then compressed further by Huffman coding.

OCR (Optical character recognition, optical character reader)

Describes devices or software that can recognise typed text, such as ordinary paper documents. Light is reflected off the document to be read, the result detected, and the patterns produced compared with ones already stored. If a match is made, the character is 'recognised' and stored as an ASCII-type code; thus the printed page is converted into a text file which can be edited (e.g. in a word processor) as required. (If the page were simply scanned conventionally and the bit image stored, it would only be possible to recall the document in its original form, not edit or reformat the text contained in it; and the file created would be inconveniently large.) The most common way to implement OCR is via a standard flatbed or hand scanner plus dedicated OCR software.

Partition

A portion of a hard disk that functions as a separate unit. A single hard disk can be divided into several partitions, each of which functions as a separate drive and has its own volume name (such as D:, E:, F:, and so on). The purpose is to make the drive more efficient, as the computer can search smaller sections for a specific file rather than the entire drive. The verb to partition refers to the process of dividing the hard drive into partitions.

Pixel

Short for Picture Element, a pixel is a single point in a graphic image. Graphics monitors display pictures by dividing the display screen into thousands (or millions) of pixels, arranged in rows and columns. The pixels are so close together that they appear connected.

The number of bits used to represent each pixel determines how many colors or shades of gray can be displayed. For example, in 8-bit color mode, the color monitor uses 8 bits for each pixel, making it possible to display 2 to the 8th power (256) different colors or shades of grey.

On color monitors, each pixel is actually composed of three dots -- a red, a blue, and a green one. Ideally, the three dots should all converge at the same point, but all monitors have some convergence error that can make color pixels appear fuzzy.

The quality of a display system largely depends on its resolution, how many pixels it can display, and how many bits are used to represent each pixel. VGA systems display 640 by 480, or about 300,000 pixels. In contrast, SVGA systems display 1,024 by 768, or nearly 800,000 pixels. True Color systems use 24 bits per pixel, allowing them to display more than 16 million different colors.

PDF (Portable Document Format)

A file format designed to enable printing and viewing of documents with all their formatting (typefaces, images, layout, etc.) appearing the same regardless of what operating system is used, so a PDF document should look the same on Windows, Macintosh, linux, OS/2, etc. The PDF format is based on the widely used Postcript document-description language. Both PDF and Postscript were developed by the Adobe Corporation.

PHP (PHP: Hypertext Preprocessor)

PHP is a programming language used almost exclusively for creating software that is part of a web site. The PHP language is designed to be intermingled with the HTML that is used to create web pages. Unlike HTML, the PHP code is read and processed by the web server software (HTML is read and processed by the web browser software.)

PNG (Portable Network Graphics)

PNG is a graphics format specifically designed for use on the World Wide Web. PNG enable compression of images without any loss of quality, including high-resolution images. Another important feature of PNG is that anyone may create software that works with PNG images without paying any fees - the PNG standard is free of any licensing costs.