The information here has been compiled from http://www.nightflight.com/foldoc/index.html.  OR from http://webopedia.internet.com  Links in the page below will take you directly there.

Bit = Short for binary digit, the smallest unit of information on a machine. The term was first used in 1946 by John Tukey, a leading statistician and adviser to five presidents. A single bit can hold only one of two values: 0 or 1. More meaningful information is obtained by combining consecutive bits into larger units. For example, a byte is composed of 8 consecutive bits..

Byte= Abbreviation for binary term, a unit of storage capable of holding a single character. On almost all modern computers, a byte is equal to 8 bits. Large amounts of memory are indicated in terms of kilobytes (1,024 bytes), megabytes (1,048,576 bytes), and gigabytes (1,073,741,824 bytes). A disk that can hold 1.44 megabytes, for example, is capable of storing approximately 1.4 million characters, or about 3,000 pages of information.

Resolution= Refers to the sharpness and clarity of an image. The term is most often used to describe monitors, printers, and bit-mapped graphic images. In the case of dot-matrix and laser printers, the resolution indicates the number of dots per inch. For example, a 300-dpi (dots per inch) printer is one that is capable of printing 300 distinct dots in a line 1 inch long. This means it can print 90,000 dots per square inch

For graphics monitors, the screen resolution signifies the number of dots (pixels) on the entire screen. For example, a 640-by-480 pixel screen is capable of displaying 640 distinct dots on each of 480 lines, or about 300,000 pixels. This translates into different dpi measurements depending on the size of the screen. For example, a 15-inch VGA monitor (640x480) displays about 50 dots per inch.

Printers, monitors, scanners, and other I/O devices are often classified as high resolution, medium resolution, or low resolution. The actual resolution ranges for each of these grades is constantly shifting as the technology improves.

Dpi= Dots per inch

A measure of resolution for printers, scanners and displays.

Pixel= picture element

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 gray.

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.

Color/Bit Depth  (from http://www.pcguide.com/ref/video/modes.htm)

Each pixel of the screen image is displayed on a monitor using a combination of three different color signals: red, green and blue. This is similar (but by no means identical) to how images are displayed on a television set. Each pixel's appearance is controlled by the intensity of these three beams of light. When all are set to the highest level the result is white; when all are set to zero the pixel is black, etc.

The amount of information that is stored about a pixel determines its color depth, which controls how precisely the pixel's color can be specified. This is also sometimes called the bit depth, because the precision of color depth is specified in bits. The more bits that are used per pixel, the finer the color detail of the image. However, increased color depths also require significantly more memory for storage of the image, and also more data for the video card to process, which reduces the possible maximum refresh rate.

This table shows the color depths used in PCs today:

True color is given that name because three bytes of information are used, one for each of the red, blue and green signals that make up each pixel. Since a byte has 256 different values this means that each color can have 256 different intensities, allowing over 16 million different color possibilities. This allows for a very realistic representation of the color of images, with no compromises necessary and no restrictions on the number of colors an image can contain. In fact, 16 million colors is more than the human eye can discern. True color is a necessity for those doing high-quality photo editing, graphical design, etc.

High color uses two bytes of information to store the intensity values for the three colors. This is done by breaking the 16 bits into 5 bits for blue, 5 bits for red and 6 bits for green. This means 32 different intensities for blue, 32 for red, and 64 for green. This reduced color precision results in a slight loss of visible image quality, but it is actually very slight--many people cannot see the differences between true color and high color images unless they are looking for them. For this reason high color is often used instead of true color--it requires 33% (or 50% in some cases) less video memory, and it is also faster for the same reason.

In 256-color mode the PC has only 8 bits to use; this would mean something like 2 bits for blue and 3 for each of green and red. Choosing between only 4 or 8 different values for each color would result in rather hideously blocky color, so a different approach is taken instead: the use of a palette. A palette is created containing 256 different colors. Each one is defined using the standard 3-byte color definition that is used in true color: 256 possible intensities for each of red, blue and green. Then, each pixel is allowed to choose one of the 256 colors in the palette, which can be considered a "color number" of sorts. So the full range of color can be used in each image, but each image can only use 256 of the available 16 million different colors. When each pixel is displayed, the video card looks up the real red, green and blue values in the palette based on the "color number" the pixel is assigned.

The palette is an excellent compromise: it allows only 8 bits to be used to specify each color in an image, but allows the creator of the image to decide what the 256 colors in the image should be. Since virtually no images contain an even distribution of colors, this allows for more precision in an image by using more colors than would be possible by assigning each pixel a 2-bit value for blue and 3-bit values each for green and red. For example, an image of the sky with clouds (like the Windows 95 standard background) would have many different shades of blue, white and gray, and virtually no reds, greens, yellows and the like.

256-color is the standard for much of computing, mainly because the higher-precision color modes require more resources (especially video memory) and aren't supported by many PCs. Despite the ability to "hand pick" the 256 colors, this mode produces noticeably worse image quality than high color; most people can tell the difference between high color and 256-color mode.

Image 1. <data, graphics> Data representing a two-dimensional scene. A digital image is composed of pixels arranged in a rectangular array with a certain height and width. Each pixel may consist of one or more bits of information, representing the brightness of the image at that point and possibly including colour information encoded as RGB triples.

Images are usually taken from the real world via a digital camera, frame grabber, or scanner; or they may be generated by computer, e.g. by ray tracing software.

See also image formats, image processing.

Gif = Graphics Interchange Format  <graphics, file format> /gif/, occasionally /jif/ (GIF, GIF 89A) A standard for digitised images compressed with the LZW algorithm, defined in 1987 by CompuServe (CIS). Graphics Interchange Format and GIF are service marks of CompuServe Incorporated. This only affects use of GIF within Compuserve, and pass-through licensing for software to access them, it doesn't affect anyone else's use of GIF. It followed from a 1994 legal action by Unisys against CIS for violating Unisys's LZW software patent. The CompuServe Vice President has stated that "CompuServe is committed to keeping the GIF 89A specification as an open, fully-supported, non-proprietary specification for the entire on-line community including the World-Wide Web".

Filename extension: .gif.

Tiff= Tagged Image File Format  <file format, graphics> (TIFF) A file format used for still-image bitmaps, stored in tagged fields. Application programs can use the tags to accept or ignore fields, depending on their capabilities.  While TIFF was designed to be extensible, it lacked a core of useful functionality, so that most useful functions (e.g. lossless 24-bit colour) requires nonstandard, often redundant, extensions. The incompatibility of extensions has led some to expand "TIFF" as "Thousands of Incompatible File Formats".

JPEG= Joint Photographic Experts Group <file format> (JPEG) The original name of the committee that designed the standard image compression algorithm. JPEG is designed for compressing either full-colour or grey-scale digital images of "natural", real-world scenes. It does not work so well on non-realistic images, such as cartoons or line drawings. JPEG does not handle compression of black-and-white (1 bit-per-pixel) images or moving pictures. Standards for compressing those types of images are being worked on by other committees, named JBIG and MPEG.

Filename extension: .jpg, .jpeg

PNG=Portable Network Graphics <file format> /ping/ (PNG) An extensible file format for the lossless, portable, well-compressed storage of raster images. PNG provides a patent-free replacement for GIF and can also replace many common uses of TIFF. Indexed-colour, greyscale and truecolour images are supported, plus an optional alpha channel. Sample depths range from 1 to 16 bits. PNG is designed for on-line viewing applications, such as the World Wide Web, so it is fully streamable with a progressive display option. PNG is robust, providing both full file integrity checking and simple detection of common transmission errors. Also, PNG can store gamma correction and chromaticity data for improved colour matching on heterogeneous platforms.

Filename extension: .png

multimedia

The use of computers to present text, graphics, video, animation, and sound in an integrated way. Long touted as the future revolution in computing, multimedia applications were, until the mid-90s, uncommon due to the expensive hardware required. With increases in performance and decreases in price, however, multimedia is now commonplace. Nearly all PCs are capable of displaying video, though the resolution available depends on the power of the computer's video adapter and CPU.

Because of the storage demands of multimedia applications, the most effective media are CD-ROMs.

hypertext

<hypertext> A term coined by Ted Nelson around 1965 for a collection of documents (or "nodes") containing cross-references or "links" which, with the aid of an interactive browser program, allow the reader to move easily from one document to another. See also hypermedia.

hypermedia

An extension of hypertext to include graphics, sound, video and other kinds of data. See also hypertext markup language, World-Wide Web.

digital audio

<multimedia, file format> A sequence of discrete samples taken from a continuous sound (audio) waveform. Tens of thousands of samples are taken each second. Each sample represents the intensity of the sound pressure wave at that instant. Apart from the sampling frequency, the other parameter is the digital encoding of each sample including the number of bits used. The encoding may be linear, logarithmic or mu-law.Digital audio is typically created by taking 16-bit samples over a spectrum of 44.1 thousand cycles per second (kHz), this means that CD quality sound requires 1.4 million bits of data per second. Digital telephone systems use lower sample rates.

Au= Short for audio, a common format for sound files on UNIX machines. It is also the standard audio file format for the Java programming language. AU files generally end with a .au extension . On PCs, two other popular sound formats are WAV and MIDI.

WAVThe format for storing sound in files developed jointly by Microsoft and IBM. Support for WAV files was built into Windows 95 making it the de facto standard for sound on PCs. WAV sound files end with a.wav extension and can be played by nearly all Windows applications that support sound.

MIDI= Pronounced middy, an acronym for musical instrument digital interface, a standard adopted by the electronic music industry for controlling devices, such as synthesizers and sound cards, that emit music. At minimum, a MIDI representation of a sound includes values for the note's pitch, length, and volume. It can also include additional characteristics, such as attack and delay time.

The MIDI standard is supported by most synthesizers, so sounds created on one synthesizer can be played and manipulated on another synthesizer. Computers that have a MIDI interface can record sounds created by a synthesizer and then manipulate the data to produce new sounds. For example, you can change the key of a composition with a single keystroke.

A number of software programs are available for composing and editing music that conforms to the MIDI standard. They offer a variety of functions: for instance, when you play a tune on a keyboard connected to a computer, a music program can translate what you play into a written score.

AIFF= Short for Audio Interchange File Format, a common format for storing and transmitting sampled sound. The format was developed by Apple Computer and is the standard audio format for Macintosh computers. It is also used by Silicon Graphics Incorporated (SGI).

The format encodes audio data in 8-bit mono or stereo waveforms. AIFF files generally end with a .AIF or .IEF extension.

The AIFF format does not support data compression so AIFF files tend to be large. However, there is another format called AIIF-Compressed (AIFF-C or AIFC) that supports compression rations as high as 6:1.

ASF Short for Advanced Streaming Format, a streaming multimedia file format developed by Microsoft. ASF has been submitted to ISO and IETF for standardization. It is expected to be an integral part of Windows 98 and eventually replace the older AVI format.

Streaming A technique for transferring data such that it can be processed as a steady and continuous stream. Streaming technologies are becoming increasingly important with the growth of the Internet because most users do not have fast enough access to download large multimedia files quickly. With streaming, the client browser or plug-in can start displaying the data before the entire file has been transmitted.
For streaming to work, the client side receiving the data must be able to collect the data and send it as a steady stream to the application that is processing the data and converting it to sound or pictures. This means that if the streaming client receives the data more quickly than required, it needs to save the excess data in a buffer. If the data doesn't come quickly enough, however, the presentation of the data will not be smooth.
There are a number of competing streaming technologies emerging. For audio data on the Internet, the de facto standard is Progressive Network's RealAudio

MP3 Is the file extension for MPEG, audio layer 3. Layer 3 is one of three coding schemes (layer 1, layer 2 and layer 3) for the compression of audio signals. Layer 3 uses perceptual audio coding and psychoacoustic compression to remove all superfluous information (more specifically, the redundant and irrelevant parts of a sound signal. The stuff the human ear doesn't hear anyway). It also adds a MDCT (Modified Discrete Cosine Transform) that implements a filter bank, increasing the frequency resolution 18 times higher than that of layer 2.
The result in real terms is layer 3 shrinks the original sound data from a CD (with a *bitrate of 1411.2 kilobits per one second of stereo music) by a factor of 12 (down to 112-128kbps) without sacrificing sound quality.
*Bitrate denotes the average number of bits that one second of audio data will consume.
Because MP3 files are small, they can easily be transferred across the Internet. Controversy arises when copyrighted songs are sold and distributed illegally off of Web sites. On the other hand, musicians may be able to use this technology to distribute their own songs from their own Web sites to their listeners, thus eliminating the need for record companies. Costs to the consumer would decrease, and profits for the musicians would increase.

Real Audio/Video The de facto standard for streaming audio and video data over the World Wide Web. RealAudio was developed by RealNetworks and supports FM-stereo-quality sound. To hear a Web page that includes a RealAudio sound file, you need a RealAudio player or plug-in, a program that is freely available from a number of places. It's included in current versions of both Netscape Navigator and Microsoft Internet Explorer.