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Glossary of Terms

Glossary of Terms

C
An acronym for Chrominance (in video signals).
C And C++
Computer programming languages. An effective language used by high-level programmers for general purposes, including complex interactive programs.
Cable
Electrical conductors such as wires and cords used to power or link various pieces of equipment.
Cable Equalization
The method of altering the frequency response of a video amplifier to compensate for high frequency losses in cables that it feeds. (See Peaking.)
Cache
A reserved section of memory used to improve performance or a temporary storage location for data requiring immediate access. A small amount of relatively high-speed storage which is used as an intermediary between the data user and a larger, slower storage device (the backing store).
CAD
An acronym for Computer Aided Design.
CAD/CAM
Acronym for Computer-Aided Design and Computer-Aided Manufacture. Software that allows users to graphically create system models, then manipulate and study the system models against predetermined criteria.
CAE
An acronym for Computer-Aided Engineering.
Capacitance
The storing of an electrical charge. At high frequencies, capacitance that exists in cables also represents a form of impedance (load or resistance).
Card
A computer board with printed circuitry and components that is plugged into a computer's system board to provide special functions or features.
Carrier
A term used to refer to various telephone companies that provide local, long distance or value added services; alternately, a system or systems whereby many channels of electrical information can be carried over a single transmission path.
Cathode-ray Tube (CRT)
A vacuum tube that produces an image when energized by an electron beam generated inside the tube. A CRT has a heater element, cathode, and grids in the neck of the tube, making up the "gun". An electron beam is produced by the gun and is accelerated toward the front display, or screen surface of the tube. The display surface contains phosphors that illuminate when bombarded by electrons in the electron beam. A CRT is commonly known as a picture tube.
CAV
An acronym for Component Analog Video or Constant Angular Velocity.
CBT
An acronym for Computer-Based Training.
CCD
An acronym for Charge-Coupled Device.
CCIR
An acronym for International Radio Consultative Committee. A global organization responsible for establishing television standards.
CCITT
An acronym for Consultative Committee for international Telegraphy and Telephony (now called the International Telecommunications Union's Telecommunications Standardization Sector or TSS), an international body responsible for establishing interoperability standards for communications systems. The CCITT is the world's leading telecommunications standards organization.
CD
An acronym for Compact Disc. (See CD-ROM.)
CD+G
An acronym for Compact Disc + Graphics. A CD format that includes the ability to utilize extended graphics as written into the original CD-ROM specifications.
CD-I
An acronym for Compact Disc-Interactive.
CD-ROM
An acronym for Compact Disc - Read Only Memory. A 4.75 inch laser-encoded optical memory storage medium with the same constant linear velocity (CLV) format as compact audio discs and some video discs. CD-ROMs can hold up to 650 megabytes of information.
CD-ROM XA
An acronym for Compact Disc-Read Only Memory Extended Architecture. An extension of the CD-ROM standard billed as a hybrid of CD-ROM and CD-I, and promoted by Microsoft. The extension adds ADPCM audio to permit the interleaving of sound and video data to animation, with sound synchronization.
CD-WORM
An acronym for Compact Disc - Write Once/Read Many. A format similar to CD-ROM that can be written to once and ready from many times.
Central Processing Unit (CPU)
A part of a computer system which contains the main storage, arithmetic unit, and special register groups. Performs arithmetic operations, controls instruction processing, and provides timing signals and other operations.
CGA
An acronym for Color Graphics Adapter.
Channel
One of the two stereo sound signals, identified as left and right, in audio systems and video and audio discs. A high-speed optical fiber or metal pathway between the host computer and the controllers of the peripheral devices.
Chapter
One independent, self-contained segment of an interactive Level I videodisc. Chapter numbers identify individual chapters by searching to a chapter stop.
Charge-Coupled Device (CCD)
Charge-coupled devices are typically used in digital cameras as an optical scanning mechanism. A CCD device consists of a shift register that stores samples of analog signals. An analog charge is sequentially passed along the device by the action of stepping voltages and stored in potential wells formed under electrodes. The charge is moved from one well to another by the stepping voltages.
Check Disc
A videodisc or CD-ROM produced before quantity replication to verify the accuracy of the design, content and coding.
Check Sum
A summation of digits, or bits, computed for the purpose of verifying the integrity of a block of data. For example, a check sum is computed on a block of data and sent with the data. At its destination, a new Check Sum in computed (using the same formula) and compared against the original Check Sum. If they don't agree, there is a data error.
Chroma
The color information on a video signal as opposed to the brightness (intensity). The characteristics of color information, independent of luminance intensity. Hue and saturation are qualities of chroma. Black, gray, and white objects do not have chroma characteristics.
Chrominance
Part of a color television signal containing the color information. Abbreviated by "C".
Chrominance-to-Burst Phase
The difference between the expected phase and the actual phase of the chrominance portion of the video signal relative to burst phase.
Chrominance-to-Luminance Delay
The difference in time that it takes for the chrominance portion of the video signal to pass through a system relative to the time it takes for the luminance portion. Also called relative chroma time.
Chrominance-to-Luminance Gain
The difference between the gain of the chrominance portion of the video signal and the gain of the luminance portion as they pass through a system.
CIF
An acronym for Common Intermediate Format.
Clipping
The process of shearing off the peaks (or excursions) of a signal.
CLV
An acronym for Constant Linear Velocity.
Coaxial Cable
A two-conductor wire in which one conductor completely wraps the other with the two separated by insulation. Constant impedance transmission cable.
Code
A formula or method used to represent information. To write a computer program.
Codec
Coder/decoder system for digital transmission.
Collimated
Refers to a light path segment where all the light rays are parallel to each other.
Color Bar
A test pattern containing six basic colors; yellow, cyan, green, magenta, red, and blue - used to check the chrominance functions of color TV systems.
Color Bust
In color systems, a burst of sub-carrier frequency located on the back porch of the composite video signal. This serves as a color synchronizing signal to establish a frequency and phase reference for the chrominance signal.
Color Contrast
Refers to the value relationship of two colors used in conjunction within a presentation slide, e.g., yellow letters on a blue background. Contrast is required for readability of text, charts and graphs. The more contrast, the better the readability.
Color Graphics Adapter (CGA)
Introduced in 1983, it was IBM's first product to display both color and graphics standard at 320 x 200 - 640 x 200. An RCA jack above the 9-pin video output connector provides NTSC video. Signal type is TTL, non-interlaced, with imagesel x line resolution of 640 x 200 and a color palette of 4/16. CGA has a horizontal scan frequency of 15.75 kHz and vertical frequency of 60Hz.
Color Mapping
A method of translating many video display monitor colors into fewer LCD projection panel colors.
Color Palette
The total number of colors possible. See Gray Scale.
Color Phase (Hue)
The correct timing relationship within a color display. Color is considered to be in phase when the hue is reproduced correctly.
Color Red
Green, Blue & Composite Sync Outputs provide analog red, green, and blue levels. 7 volt P-P video output signals and negative-going 4 volts P-P non-terminated. and 2.3 volts P-P terminated TTL level composite sync output, matching the input standards of most data monitors and projectors. On the RGB-120 and RGB-202xi interfaces, sync is automatically stripped from any input computer signal that has sync included on the green channel. With sync on the green channel, some large screen data monitors and projectors may display a greenish tint, as well as a pulling to the right at the top or bottom. Stripping sync from the green video and using the separate sync output on those interfaces solves these problems. Sync can be added to the green channel by setting the "Sync On Green" switch.
Color Resolution
The number of colors available at once in an image, measured in terms of bits per imagesel.
Color Stripe
LCD, TFT, or STN with RGB sub-imagesels making additive color using tiny red, green, and blue windows in front of each sub-imagesel.
Color Sub-Carrier
A 3.58 MHz signal interwoven with a standard NTSC monochrome signal that contains color information.
Comb Filter
So called because of the shape of its frequency response, the Comb Filter provides a better method of separating Y and C than a chroma bandpass filter or chroma trap. There is produces better quality video with less crawling or "zipper" artifacts.
Commission Internationale de l'Eclairage (CIE or The International Commission on Illumination)
The organization responsible for the chroma diagram of 1939. A measurement format for describing color. Of the two standards (1931 & 1976), IFS uses the 1931 scale. A three dimensional diagram that defines light and color. Other systems have been developed by CIE more recently.
Common Intermediate Format
An international standard for video display formats developed by TSS. The QCIF format, which employs half the CIF spatial resolution in both horizontal and vertical directions, is the mandatory H.261 format. QCIF is used for most desktop videoconferencing applications where head and shoulder pictures are sent from desk to desk. QCIF displays 176 imagesels grouped in 144 non-interlaced luminance lines.
Compact Disc (CD)
Also referred to as compact audio disc. A 4.75 inch optical disk that contains information encoded digitally in the CLV format.
Compact Disc-Interactive
A format that provides audio, digital data, still graphics and limited motion video. A compact disc format that stores audio, still graphics, digital data and limited motion video that can be controlled or accessed by a special computer code.
Compatible
Term used to describe different hardware devices or software formats that can be utilized together without modification.
Component Analog Video
Component video signals in which an analog voltage or current (rather than a set of numbers) represents the value of a imagesel. Encoded video signals which can provide greater color resolution than composite video. NTSC encoder must be used to convert the signals. The Videodisc rotates at a constant speed, regardless of the position of the reading head. CAV format discs allow each frame (of 54,000) to be addressed individually. CAV discs revolve continuously at 1800 rpm (NTSC) AND 1500 RPM (PAL), one revolution per frame. Program time is 30 minutes per side on a 12-inch disc, 14 minutes per side on a 8-inch disc. Component video signals in which an analog voltage or current (rather than a set of numbers) represents the value of the imagesel, the same as ""analog components.
Component Video
A color television system starts with three channels of information; Red, Green, & Blue (RGB). In the process of translating these channels to a single composite video signal they are often first converted to Y, R-Y, and B-Y. Both 3-channel systems, RGB and Y, R-Y, B-Y are component video signals. They are the components that eventually make up the composite video signal. Much higher program production quality is possible if the elements are assembled in the component domain.
Composite Sync
A signal consisting of horizontal sync pulses, vertical sync pulses, and equalizing pulses with no signal reference level.
Composite Video
A mixed signal comprised of the luminance black and white, chrominance (color), blanking pulses, sync pulses and color burst. Combines the synchronization (horizontal & vertical) as well as the chrominance & luminance onto a single wire.
Compression
The process of reducing the information content of a signal so that it occupies less space on a transmission channel or storage device and a fundamental concept of video communications. An uncompressed NTSC signal requires about 90 Mbps of throughput, greatly exceeding the speed of all but the fastest and shortest of today's networks. Squeezing the video information can be accomplished by reducing the quality (sending fewer frames in a second or displaying the information in a smaller window) or by eliminating redundancy.
Computer-Aided Design (CAD)
The use of the computer system for graphic design.
Computer-Based Training (CBT)
The use of a computer to facilitate training and/or instruction. Also known as computer-aided (or assisted) instruction (CAI).
Computer Graphics
Visual images produced by a computer. Graphics standards for IBM-compatible PCs include CGA, EGA, VGA, SVGA, XGA, SXGA and UXGA.
Computer-Video Interface
A device which converts the "nonstandard" video output of computer systems to a "standard" RGB analog signal that can then be connected to a compatible data monitor or projector.
Constant Angular Velocity
The Videodisc rotates at a constant speed, regardless of the position of the reading head. CAV format discs allow each frame (of 54,000) to be addressed individually. CAV discs revolve continuously at 1800 RPM (NTSC) and 1500 RPM (PAL), one revolution per frame. Program time is 30 minutes per side on a 12-inch disc, 14 minutes per side on a 8-inch disc. Component video signals in which an analog voltage or current (rather than a set of numbers) represents the value of the imagesel, the same as analog components.
Constant Linear Velocity
Videodisc format that allows twice as much play time (up to one hour) per side as the CAV format, but without many of the user-control capabilities. The CLV disc can be read in linear play only but can provide search by chapter. CLV discs range in speed from 1800 RPM at the center track to 600 RPM at the outer edge. Playing time is 60 minutes per side on a 12-inch disc or 20 minutes per side on an 8-inch disc.
Contrast
The range of light and dark values in a picture or the ratio between the maximum and the minimum brightness values. Low contrast is shown mainly as shades of gray, white high contrast is shown as blacks and whites with very little gray. It is also a TV monitor adjustment which increases or decreases the level of contrast of a televised picture.
Contrast Ratio
The ratio of the maximum white to the minimum black level possible for a particular spot on the image with the background light levels factored out. This is the ratio of the highlight output level divided by the low light output level. In theory, the contrast ratio of the television system should be at least 100:1, if not 300:1. There are several limitations. In the CRT, light from adjacent elements contaminates the area of each element. Room ambient light contaminates light emitted from the CRT. Well-controlled viewing conditions should yield a practical contrast ratio of 30:1 to 50:1.
Controller
A specialized computer or processor that controls the transfer of information between a computer and one or more memory devices. The controller is the circuitry that finds, analyzes, and executes the instructions in a computer program.
Convergence
The alignment of the Red, Green and Blue video on a projected display.
Coupling
The method of connecting two circuits together. Circuits connected with a wire are directly coupled; circuits connected through a capacitor or a transformer are indirectly (or AC) coupled.
Courseware
Instructional software and support materials needed to deliver a course or instructions module.
CPS
An acronym for Characters Per Second.
CPU
An acronym for Central Processing Unit.
Crosshatch
A test pattern consisting of vertical and horizontal lines used for converging a color display device.
CRT
An acronym for Cathode Ray Tube.
CSMA/CD
Carrier Sense Media Access/Collision Detection. The Network Layer protocol used on most LANs.
Cursor
An indicator on a display that marks the current active position. A symbol (usually a cross-hair, horizontal bar or vertical bar) indicates where characters or the drawing will next appear on the screen.
Cut-And-Paste
A method of moving a portion of a document (text and/or graphics) into another document or another location with the same document.
CYMK
Cyan, Yellow, Magenta and Black - See Subtractive Color.
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