Glossary of Acronyms

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

CAM - Common Access Method. A committee formed in 1988 that consists of a number of computer peripheral suppliers and is dedicated to developing standards for a common software interface between SCSI peripherals and host adapters. The CAM committee also has set a standard for IDE drives called the ATA interface.

CAM - Constant Addressable Memory. Synonym for Associative Memory. A table that is accessed not via an explicit index, but by the data it contains. If no entries of the associative memory match the input data, a miss signal is asserted. If any entries of the associative memory match the input data, the associative memory indicates the match, and produces any related data that was stored in that entry.

CAP - Carrierless Amplitude and Phase Modulation. The first implementation of ADSL (Asynchronous Digital Subscriber Line).

CAV - Constant Angular Velocity. An optical disk recording format where the data is recorded on the disk in concentric circles. CAV disks are rotated at a constant speed. This is similar to the recording technique used on floppy disk drives. CAV limits the total recorded capacity compared to CLV (Constant Linear Velocity), which is also used in optical recording.

CBCP - Callback Control Protocol. A protocol that negotiates callback information with a remote client.

CBIOS - Compatibility BIOS. The IBM XT/286 and PS/2 models with 80286 or higher processors contain two separate BIOSes. The CBIOS is a real-mode BIOS which is compatible with the earlier products in the IBM PC family and PS/2 models with 8086 processors. See also ABIOS.

CBR - Constant Bit Rate. Provides data at a guaranteed rate with rigorous latency control.

CCD - Charged Coupled Device.

CCITT - The International Telegraph and Telephone Consultative Committee or the Consultative Committee for International Telegraph and Telephone. An international committee organized by the United Nations to set international communications recommendations, which frequently are adopted as standards, and to develop interface, modem, and data network recommendations. The Bell 212A standard for 1200 BPS communication in North America, for example, is observed internationally as CCITT V.22. For 2400 bps communication, most U.S. manufacturers observe V.22bis, and V.32 and V.32bis are standards for 9600 and 14400 bps, respectively. Work is now under way to define a new standard for 19200 bps called V.32fast.

The CCITT produces technical standards, known as Recommendations for all internationally controlled aspects of analog and digital communications. The ISO used standards established by the CCITT to develop the MHS (Message Handling System) standard for the OSI. The current MHS standard is called X.400. The X.500 standard will soon be implemented and resolve some incompatibility problems of post office box addresses in the E-mail services around the world.

CCP - Compression Control Protocol. Protocol that negotiates compression with a remote client.

CCS - Common Command Set. A set of SCSI commands specified in the ANSI SCSI-1 Standard X3.131-1986 Addendum 4.B. All SCSI devices must be capable of using the CCS in order to be fully compatible with the ANSI SCSI-1 standard.

CD-DA - Compact Disc Digital Audio. CD-DA is also known as "Red Book Audio" and is the digital sound format used by audio CDs. CD-DA uses a sampling rate of 44.lKHz and stores 16 bits of information for each sample. CD audio is not played through the computer, but through a special chip in the CD-ROM drive. Fifteen minutes of CD-DA sound can require about 80M. The highest quality sound that can be utilized by multimedia PCs is the CD-DA format at 44.lKHz sample rate.

CD-R - Compact Disc Recordable. Sometimes also called CD-Writable. CD-R disks are compact discs that can be recorded several times and read as many times as desired. CD-R is part of the Orange Book Standard defined by ISO. CD-R technology is used for mass production of multimedia applications. CD-R discs can be compatible with CD-ROM, CD-ROM XA, and CD audio. Orange Book specifies multi-session capabilities, which allows data recording on the disk at different times in several recording sessions. Kodak's Photo CD is an example of CD-R technology, and fits up to 100 digital photographs on a single CD. Multi-session capability allows several rolls of 35mm film to be added to a single disc on different occasions.

CD-ROM - Compact Disc Read-Only Memory. A computer peripheral device that employs compact disc (CD) technology to store large amounts of data for later retrieval. Phillips and Sony developed CD-ROM in 1983. Current CD-ROM discs hold approximately 600M of information. CD-ROM drives are much slower than conventional hard disks, with normal average access times of 380 milliseconds or greater and data transfer rates of about 1.2 megabits per second. Most CD-ROM drives use the SCSI (Small Computer Systems Interface).

CD-ROM XA - Compact Disc Read Only Memory Extended Architecture. The XA standard was developed jointly by Sony, Phillips, and Microsoft in 1988. XA is a built-in feature of newer CD-ROM drives, and supports simultaneous sound playback with data transfer. Non-XA drives support either sound playback or data.

CEC - Customer Engineering Cylinder. This is the last cylinder in P-CHS mode. IBM has always reserved this cylinder for use of disk diagnostic programs. Many BIOS do not account for it correctly. It is of questionable value these days and probably should be considered obsolete. There is no CEC reserved in the L-CHS address. Beware of diagnostic programs that don't realize they are operating in L-CHS mode and think that the last L-CHS cylinder is the CEC.

CERN - Conseil Europeen pour la Recherche Nucleaire (The European Laboratory for Particle Physics). This is the site in Geneva where the World Wide Web was created in 1989.

CERT - Computer Emergency Response Team. The CERT was formed by ARPA in November 1988 in response to the needs exhibited during the Internet worm incident. The CERT charter is to work with the Internet community to facilitate its response to computer security events involving Internet hosts, to take proactive steps to raise the community's awareness of computer security issues, and to conduct research targeted at improving the security of existing systems. CERT produces and services include 24 hour technical assistance for responding to computer security incidents, product vulnerability assistance, technical documents, and tutorials. In addition, the team maintains a number of mailing lists, and provides an anonymous FTP server where security related documents and tools are archived.

CGA Color Graphics Adapter. A type of PC video display adapter introduced by IBM on August 12, 1981, that supports text and graphics. Text is supported at a maximum resolution of 8Ox25 characters in 16 colors with a character box of 8x8 pixels. Graphics is supported at a maximum resolution of 320x200 pixels in 16 colors or 640x200 pixels in 2 colors. The CGA outputs a TTL (digital) signal with a horizontal scanning frequency of 15.75 KHz, and supports TTL color or NTSC composite displays.

CGI - Common Gateway Interface. Standard mechanism for extending Web server functionality by executing programs or scripts on the Web server in response to Web browser requests. A common use of CGI is in form processing, where the browser sends the form data to a CGI script on the server, and the script integrates the data with a database and sends back a results page as HTML.

CHAP - Challenge Handshake Authentication Protocol. Protocol used to negotiate the most secure form of encrypted authentication supported by both server and client.

CHS - Cylinder Head Sector. Method used by int13 software interface to number and identify a specific sector on a hard drive. This system is used by the BIOS to communicate with the hard drive. Standard CHS have less than 1024 cylinders, while Extended CHS have greater than 1024 cylinders. The term used to describe the non-translating scheme used by the BIOS to access to IDE drives that are less than or equal to 528MB in capacity.

CHS is the traditional way to address sectors on a disk. There are two types of CHS addressing. The CHS that is used at the INT 13H interface and the CHS that is used at the ATA device interface. In the MFM, RLL, ESDI, and early ATA days, the CHS used at the INT 13H interface was the same as the CHS used at the device interface.

Today we have CHS translating BIOS types that can use one CHS at the INT 13H interface and a different CHS at the device interface. These two types of CHS are called the logical CHS, or L-CHS, and the physical CHS, or P-CHS. L-CHS is the CHS used at the INT 13H interface, and P-CHS is the CHS used at the device interface.

The L-CHS used at the INT 13H interface allows up to 1024 cylinders, 256 heads, and 63 sectors. This allows support up to 8 GB drives. This scheme started with either ESDI or SCSI adapters many years ago. The P-CHS used at the device interface allows up to 65535 cylinders, 16 heads, and 63 sectors. This allows access to 2*28 sectors (136 GB) on an ATA device. When P-CHS is used at the INT 13H interface, it is limited to 1024 cylinders, 16 heads, and 63 sectors. This is where the old 528 barrier originated.

ATA devices may also support LBA at the device interface. LBA allows access to approximately 2*28 sectors (136 GB) on an ATA device. A SCSI host adapter can convert a L-CHS directly to an LBA used in the SCSI read/write commands. On a PC today, SCSI is then also limited to 8 GB when CHS addressing is used at the INT 13H interface.

CIDR - Class Inter-domain Routing. A proposal, set forth in RFC 1519, to allocate IP addresses so as to allow the addresses to be aggregated when advertised as routes. It is based on the elimination of intrinsic IP network addresses, that is, the determination of the network address based on the first few bits of the IP address.

CIS - Card Information Structure. The formatted information on a PCMCIA card that lets system software read a card's capabilities and configuration requirements.

CISC - Complex Instruction-Set Computer. Refers to traditional computers that operate with large sets of processor instructions. Most modern computers, including the Intel 80xxx processors, are in this category. CISC processors have expanded instruction sets that are complex in nature and require several to many execution cycles to complete. This structure contrasts with RISC (Reduced Instruction Set Computer) processors, which have far fewer instructions that execute quickly.

CLKMUL - Clock Multiplier. The factor used to indicate, or set, the CPU clock speed (internal clock) in relation to the motherboard clock speed (external clock). Both these speeds must work in relationship to the motherboard expansion bus speed (PCI, EISA, etc.) and main memory speed. Clock speeds are always given in terms of MHz (millions of cycles per second). Clock multipliers are either 1.0, 1.5. 2.0, 2.5, or 3.0. As an example, a P-75 MHz CPU running on a 50 MHz external clock setting uses a multiplier of 1.5. A P-133 MHz CPU running on a 66 MHz external clock setting uses a multiplier of 2.0.

CLNP - Connectionless Network Protocol. The OSI protocol for providing the OSI Connectionless Network Service (datagram service). CLNP is the OSI equivalent to Internet IP, and is sometimes called ISO IP.

CLTP - Connectionless Transport Protocol. Provides for end to end Transport data addressing (via transport selector) and error control (via checksum), but cannot guarantee delivery or provide flow control.

CLV - Constant Linear Velocity. An optical recording format where the spacing of data is consistent throughout the disk, and the rotational speed of the disk varies depending on what track is being read. Additionally, more sectors of data are placed on the outer tracks compared to the inner tracks of the disk, which is similar to Zone Recording on hard drives. CLV drives will adjust the rotational speed to maintain a constant track velocity as the diameter of the track changes. CLV drives rotate faster near the center of the disk and slower toward the edge. Rotational adjustment maximizes the amount of data that can be stored on a disk. CD audio and CD-ROM use CLV recording.

CMIP - Common Management Information Protocol. An OSI distributed network management protocol but much less frequently used than SNMP.

CMOS - Complementary Metallic Oxide Semiconductor. This is a chip on which basic system parameters are stored, including memory, floppy disks, harddisks, video, date, and time. The ROM BIOS is one program stored on the CMOS chip which never (should) loses its information. To perform its tasks, the BIOS needs to know various parameters (hardware configuration). These are permanently saved in a little piece (64 bytes) of CMOS RAM (short: CMOS). The CMOS power is supplied by a little battery, so its contents will not be lost after the PC is turned off. Therefore, there is a battery and a small RAM memory on board. The memory was in earlier times a part of the clock chip, now it's part of such a highly Integrated Circuit (IC). CMOS is the name of a technology which needs very low power so the computer's battery is not too much in use.

Actually, there is not a battery on new boards, but an accumulator (NiCad in most cases). It is recharged every time the computer is turned on. If your CMOS is powered by external batteries, be sure that they are in good operating condition. Also, be sure that they do not leak. That may damage the motherboard. Otherwise, your CMOS may suddenly "forget" its configuration and you may be looking for a problem elsewhere. In the monolithic PC and PC/XT, this information is supplied by setting the DIP (Dual-In-line Package) switches at the motherboard or peripheral cards. Some new motherboards have a technology named the Dallas Nov-Ram. It eliminates having an on-board battery: There is a 10 year lithium cell epoxyed into the chip.

CMOT - CMIP Over TCP. An effort to use the OSI network management protocol to manage TCP/IP networks.

CNE - Certified NetWare Engineer.

CNI - Coalition for Networked Information. A consortium formed by American Research Libraries, CAUSE, and EDUCOM to promote the creation of, and access to, information resources in networked environments in order to enrich scholarship and enhance intellectual productivity.

CO - Central Office. The facility at which individual telephone lines in a limited geographic area are connected to the public telephone network.

CODEC - COder/DECoder. A device that converts voice signals from their analog form to digital signals acceptable to more modern digital PBXs and digital transmission systems. It then converts those digital signals back to analog so that you can hear and understand what the other party is saying.

COM - Communications Port. A serial port used for both communications input and output. There are normally two COM ports with each computer, COM 1 and COM 2.

CORBA - Common Object Request Broker Architecture. An advanced policy and profile driven distributed network management architecture based that permits multiple management domains and includes extensive security features.

CPS - Characters Per Second. A data transfer rate generally estimated from the bit rate and the character length. At 2400 bps, for example, 8-bit characters with start and stop bits (for a total of 10 bits per character) are transmitted at a rate of approximately 240 characters per second (cps). Some protocols, such as V.42 and MNP, employ advanced techniques such as longer transmission frames and data compression to increase cps.

CPU - Central Processing Unit. The computer's microprocessor chip, the brains of the outfit. Typically, an IC using VLSI (very-large-scale integration) technology to pack several different functions into a tiny area. The most common electronic device in the CPU is the transistor, of which several thousand to several million or more are found. The component (chip) that is the brains of the computer and where computations are performed, or a chip or circuit that interprets and executes program instructions.

CRC - Cyclic Redundancy Checking. An error-detection technique consisting of a cyclic algorithm performed on each block or frame of data by both sending and receiving modems. The sending modem inserts the results of its computation in each data block in the form of a CRC code. The receiving modem compares its results with the received CRC code and responds with either a positive or negative acknowledgment. In the ARQ protocol implemented in high-speed modems, the receiving modem accepts no more data until a defective block is received correctly. An error detection code that is recorded within each sector of the hard drive and used to see whether parts of a string of data are missing or erroneous.

CRT - Cathode Ray Tube A device that contains electrodes surrounded by a glass sphere or cylinder and displays information by creating a beam of electrons that strike a phosphor coating inside the display unit. This device is most commonly used in computer monitors and terminals.

CSMA/CD - Carrier Sense Multiple Access with Collision Detection. The access method used by local area networking technologies such as Ethernet. Ethernet cable access protocol for a node accessing the network.

CSU/DSU - Customer Service Unit/Data Service Unit. The equivalent to a modem for a digital line.

CWIS - Campus Wide Information System. A CWIS makes information and services publicly available on campus via kiosks, and makes interactive computing available via kiosks, interactive computing systems and campus networks. Services routinely include directory information, calendars, bulletin boards, and databases.

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Compiled by Scott McArdle, MagnaCom Limited. I hope this list has helped you and if there is an item that should be on this list, please let me know. Thanks. PS, I've spent 100's of hours maintaining this list, please don't be a LAMER.