Glossary

CARTRIDGE
A cartridge is a case that contains multiple components, including recordable tape.

CCITT
Abbreviation of Comité Consultatif International Téléphonique et Télégraphique, an organization that sets international communications standards. CCITT, now known as ITU (the parent organization) has defined many important standards for data communications, including the following:

· Group 3: The universal protocol for sending fax documents across telephone lines. The Group 3 protocol specifies CCITT T.4 data compression and a maximum transmission rate of 9,600 baud. There are two levels of resolution: 203 by 98 and 203 by 196.

· Group 4 : A protocol for sending fax documents over ISDN networks. The Group 400 protocol supports images of up to 400 dpi resolution.

· V.21: The standard for full-duplex communication at 300 baud in Japan and Europe. In the United States, Bell 103 is used in place of V.21.

· V.22 : The standard for half-duplex communication at 1,200 bps in Japan and Europe. In the United States, the protocol defined by Bell 212A is more common.

· V.22bis : The worldwide standard for full-duplex modems sending and receiving data across telephone lines at 1,200 or 2,400 bps.

· V.29: The standard for half-duplex modems sending and receiving data across telephone lines at 1,200, 2,400, 4,800, or 9,600 bps. This is the protocol used by fax modems.

· V.32 : The standard for full-duplex modems sending and receiving data across phone lines at 4,800 or 9,600 bps. V.32 modems automatically adjust their transmission speeds based on the quality of the lines.

· V.32bis: The V.32 protocol extended to speeds of 7,200, 12,000, and 14,400 bps.

· V.34 : The standard for full-duplex modems sending and receiving data across phone lines at up to 28,800 bps. V.34 modems automatically adjust their transmission speeds based on the quality of the lines.

· V.42 : An error-detection standard for high-speed modems. V.42 can be used with digital telephone networks. See MNP for a competing standard.

· V.42bis: A data compression protocol that can enable modems to achieve a data transfer rate of 34,000 bps.

· V.90: The standard for full-duplex modems sending and receiving data across phone lines at up to 56,600 bps.

· X.25: The most popular packet-switching protocol for LANs. Ethernet, for example, is based on the X.25 standard.

· X.400: The universal protocol for e-mail. X.400 defines the envelope for e-mail messages so all messages conform to a standard format.

· X.500: An extension to X.400 that defines addressing formats so all e-mail systems can be linked together.

CD (Compact Disc or compact audio disc)
A 4.75-inch (12cm) optical disc that contains information (usually musical) encoded digitally in the constant linear velocity (CLV) format. This popular format for high-fidelity music offers 90 dB signal/noise ratio, 74 minutes of digital sound, and no degradation of quality from playback. The standards for this format (developed by NV Philips and Sony Corporation) are known as the Red Book.
The official (and rarely used) designation for the audio-only format is CD-DA (compact disc-digital audio). The simple audio format is also known as CD-A (compact disc-audio). A smaller (3") version of the CD is known as CD-3.

CD+G (Compact Disc-Graphics)
A CD format that includes extended graphics capabilities as written into the original CD-ROM specifications. Includes limited video graphics encoded into the CD subcode area. Developed and marketed by Warner New Media.

CD-i (Compact Disc-Interactive)
A compact disk format released in October 1991 that provides audio, digital data, still graphics, and motion video. The standards for this format (developed by NV Philips and Sony Corporation) are known as the Green Book.

CD+MIDI (Compact Disc-Musical Instrument Digital Interface)
A CD format that adds to the CD+G formats digital audio, graphics information, and musical instrument digital interface (MIDI) specifications and capabilities. Developed and marketed by Warner New media.

CDPD
Short for Cellular Digital Packet Data, a data transmission technology developed for use on cellular phone frequencies. CDPD uses unused cellular channels (in the 800- to 900-MHz range) to transmit data in packets. This technology offers data transfer rates of up to 19.2 Kbps, quicker call set up, and better error correction than using modems on an analog cellular channel.

CD-ROM (Compact Disc-Read Only Memory)
A 4.75-inch laser-encoded optical memory storage medium with the same constant linear velocity (CLV) spiral format as audio CDs and some videodiscs, CD-ROMs can hold about 550 megabytes of data. CD-ROMs require more error-correction information than the standard prerecorded compact audio disc.
The standards for this format (developed by NV Philips and Sony Corporation) are known as the Yellow Book. See also CD-ROM XA.

CD-ROM drive or CD-ROM player
A device that retrieves data from a CD-ROM disc; differs from a standard audio CD player by the incorporation of additional error-correction circuitry. CD-ROM drives usually can also play music from audio CDs.

CD-ROM XA
(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 Sony and Microsoft. The extension adds ADPCM audio from CD-i and permits the interleaving of sound and video data for animation and sound synchronization.

CD-ROM XA
(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 Sony and Microsoft. The extension adds ADPCM audio from CD-i and permits interleaving of sound and video data for animation and sound synchronization.

CD Video
A CD format introduced in 1987 that combined 20 minutes of digital audio and six minutes of analog video on a standard 4.75-inch CD. Upon introduction, many firms renamed 8- inch and 12-inch videodiscs as CDV, in an attempt to capitalize on the consumer popularity of the audio CD. The term fell out of use in 1990 and was replaced in some part by laserdisc.

CD-WO (Compact Disc-Write Once)
A variant on CD-ROM that can be written to once and read many times; developed by NV Philips and Sony Corporation. Also known as CD-WORM (CD-write once/read many). Standards for this format are known as the Orange Book.

Centronics Interface
A standard interface for connecting printers and other parallel devices. Although Centronics Corporation designed the original standard, the Centronics interface used by modern computers was designed by Epson Corporation. For PCs, almost all parallel ports conform to the Centronics standard. Two new parallel port standards that are backward compatible with Centronics, but offer faster transmission rates, are ECP (Extend Capabilities Port) and EPP (Enhanced Parallel Port).

Chroma format
Defines the number of chrominance blocks in a macroblock.

Chrominance
Portion of a video signal that carries color information (hue and saturation, but not brightness). A matrix, block, or single pel represents one of the two color-difference signals related to the primary colors as defined in the bitstream. The symbols used for the color difference signals are Cr and Cb. See also YCbCr.

CIF (Common Image Format)
The standard sample structure that represents the picture information of a single frame in digital HDTV, independent of frame rate and sync/blank structure. The uncompressed bit rate for transmitting CIF at 29.97 frames/sec is 36.45 Mbps.

Coded order
The order in which pictures are stored and decoded. This order is not necessarily the same as the display order.

Coding parameters
The set of user-definable parameters that characterize a coded video bitstream. While bitstreams are characterized by coding parameters, decoders are characterized by the bitstreams they are capable of decoding.

COM

Abbreviation of Component Object Model.
In DOS systems, COM refers to the name of a serial communications port. DOS supports four serial ports: COM1, COM2, COM3, and COM4. However, most software uses system interrupts to access the serial ports, and there are only two IRQ lines reserved. This means that the four COM ports share the same two IRQ lines. Typically, COM1 and COM3 use IRQ4, while COM2 and COM4 use IRQ3. So in general, if you have two devices, one of which is attached to COM1 and the other to COM3, you cannot use them simultaneously.

Component
A matrix, block, or single pel from one of the three matrices (one for luminance and two for chrominance) that make up a picture.

Component video
The separation of chrominance (color) and luminance parts of the video signal. In component video, these two signals are recorded separately, which helps maintain better picture quality over more generations.

Composite video
The complete visual wave form of the color video signal composed of chrominance and luminance picture information; blanking pedestal; field, line, and color sync pulses; and field equalizing pulses. See also RGB.

Compression ratio
The size of the original image divided by the size of the compressed image, measuring the degree to which a compression routine can reduce the size of a file.

Computer-based training (CBT)
The use of a computer to deliver instruction or training; also known as Computer-Aided (or assisted) Instruction (CAI), Computer-Aided Learning (CAL), Computer-Based Instruction (CBI), and Computer- Based Learning (CBL).

Constant bitrate
Operation in which the bitrate is constant from start to finish of a compressed bitstream.

Constant bitrate coded video
A compressed video bitstream with a constant average bitrate.

Courseware
Instructional software, including all discs, tapes, books, charts, and computer programs necessary to deliver a complete instructional module or course.

CRC (cyclic redundancy code)
A code used for error detection and correction.

CREDIT CARD MEMORY
Credit card memory is designed for use in laptop and notebook computers. Because of its compact form factor, credit card memory is ideal for applications where space is limited. (Credit card memory got its name because the form factor is the approximate size of a credit card.)

CTI
Short for computer-telephony-integration, which refers to systems that enable a computer to act as a call center, accepting incoming calls and routing them to the appropriate device or person. Today's CTI systems are quite sophisticated and can handle all sorts of incoming and outgoing communications, including phone calls, faxes, and Internet messages.