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INTERNET GLOSSARY

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					INTERNET GLOSSARY

Archie
A play on the word 'archive', it is a distributed database of archive files.
Bitnet
An education and research network that makes up part of the Internet, mainly used for email & listservs.
Bandwidth
A measurement of a network's transmission speed, how much data a network can transfer in a given
amount of time?
Baud rates
The number of transitions per second made by a modem.
Bits per second (BPS)
Measurement of the data transmission for a modem or network.
Bookmark
The process of saving a URL in your Web browser. Allows the user to return to a particular site or entry
by making a record of it.
BTW
Abbreviation for "By the Way" used in e-mail, newsgroup, and chat communication.
Bulletin board system
A service dedicated to a specific topic where users post messages that are read by others. It is a
computer or computers that offer dial-in communication which offers users the ability to send e-mail, use
news-groups, and sometimes access the Internet.
Client-server
Two computer systems linked by a network or modem connection where the client computer uses
resources by sending requests to the server computer.
Database
A collection of information stored oftentimes in a computerized format. Examples: library catalogs, search
engines, financial data, etc.
Dial-up service
A common method of connecting to the Internet. A user's modem dials up to a service provider, through
which an Internet connection is established.
Domain name
The name of a computer or server on the Internet in the form of a string of names or numbers, separated
by periods.
Download
The transfer a file or files from a remote computer to the user's computer.
DNS
Abbreviation for Domain Name System. A distributed client-server database system which links domain
names with their numerical IP addresses.
E-mail
Abbreviation for electronic mail. A letter or memo sent to a person or group electronically on the Internet.
E-mail address
A user's electronic mailbox name or address, needed for linking the sender of e-mail and the recipient.
FAQ
Abbreviation for Frequently Asked Questions. A document (often a hypertext document) containing
common questions and answers for a particular website or topic.
Flame
Personal verbal attacks on other Internet users, via e-mail, USENET, or mailing lists. Flame wars occur
when a series of flames are sent back and forth between two or more people.
Finger
Internet service that provides information about the users on a particular computer.
Freeware
Software that is available (free of charge) for personal use.
FTP (File Transfer Protocol)
An Internet tool/software utility that allows you to transfer files between two computers that are connected
to the Internet. Anonymous FTP allows you to connect to remote computers and to transfer publicly
available computer files or programs.
Gateway
A computer system that connects two incompatible services such as a commercial online service and the
Internet.
GIF
Graphical Interchange Format is a commonly used graphics file format for image files on the Internet.
Gopher
A play on the words "go for." A text menu-based browsing service on the Internet. The user selects an
item on the menu and is led to either a file or another menu.
Home page
The main page of hypertext-based information for n individual or organization on the World Wide Web
(WWW).
Hot list
Similar to a bookmark in Gopher or Netscape, this list makes note of particular pages on the WWW that
are accessed when using the Mosaic browser.
HTML (Hypertext Markup Language)
The coding applied to text a file that allows them to appear as formatted hypermedia documents on the
World Wide Web.
HTTP
Abbreviation for Hyper Text Transfer Protocol. Often this is the initial sequence of letters in a web
address.
Hypermedia
A system for storing information using embedded references to other pages, sounds, and graphics used
on the WWW.
Hypertext
The text-based version of hypermedia.
Internaut
Slang for someone who is an experienced Internet user.
Internet
The worldwide-interconnected system of computer networks.
Internet address (a.k.a. IP address)
An assigned series of numbers unique to each computer on the Internet which is used to identify it for
data exchanges.
IP
Abbreviation for Internet Protocol. A protocol that ensures data goes where it is supposed to go on the
Internet.
IRC
Abbreviation for Internet Relay Chat. An Internet service accessed through software programs that
features real-time communication on channels devoted to specific topics.
LAN
Abbreviation for Local Area Network. Used to connect computers over a short distance such as
computers within the same company or office.
LISTSERV
An e-mail list server. A computer program that maintains lists of e-mail addresses in order that users can
participate in an electronic discussion or conference. There are thousands of listserve on all imaginable
topics.
Login
The process entering in information related to an account name and its password in order to access a
time-sharing computer.
Mailing list
An e-mail system that includes multiple recipients as part of its address. See e-mail.
Mosaic
A browser program developed by the National Center for Supercomputing Applications that provides the
internet user with a point-and-click interface to WWW, Gopher, FTP, and other Internet services
Newbie
Slang for someone who is new to the Internet or a specific aspect of it.
Newsgroup
A Usenet discussion group that is related to one topic. Internet users can subscribe to many different
newsgroups. Major newsgroup categories include:
         alt:     "Alternative" discussions on a wide variety of topics.
         comp: Computer-related information and discussion.
         misc: "Miscellaneous" categories.
         news: Issues concerning USENET and newsgroups
         rec:     Recreational activities, such as movies, books, sports, etc.
         sci:     Science news and information.
         soc:     Topics related to sociology and psychology.
         talk:    USENET's version of talk radio.
Netiquette
The unwritten "rules" of etiquette used on the Internet.
NetScape
A graphical World Wide Web browser for Macintosh, Microsoft Windows, and Amiga systems.
Network
A set of computers that all use the same protocol in order to exchange information among themselves.
Password
Secret code of letters and numbers needed to gain access to a time-sharing computer or FTP system, or
to protect Web pages.
Ping
Packet InterNet Groper is a program and UNIX command that helps testing and debugging network
and/or Internet connections. An 'Echo' command is sent to a specified computer and then waits for a
response. The result is a report that displays the success or failure, usually a report back of a timed
response in seconds, of the intended action.
Posting
Can refer to a message or article that appears on a newsgroup or message board system, or the act of
sending an electronic message to a newsgroup or message board.
PPP
Abbreviation for Point to Point Protocol. It is a protocol used for sending information via a modem which is
connected to the Internet.
Protocol
The rules make possible the exchange of messages between users on the Internet, or within any given
network.
Search Engine
A tool or program which allows keyword searching for relevant sites or information on the Internet.
General and topic-specific search engines are prevalent today, for example, Education World,
WebCrawler, Infoseek, Lycos, and Yahoo are examples of search engines.
Service provier
A company that provides dial-up or direct access to the Internet for a fee. Sometimes referred to as ISP
(internet service provider).
Shareware
Copyrighted software that is available for personal use for a small fee, and often downloadable from the
Internet.
SLIP
Stands for Serial Line Internet Protocol. Similar PPP, this is another protocol that is used with a modem to
establish an IP connection to the Internet.
Snail mail
Slang for regular, paper mail sent through the postal services.
TCP
Stands for Transmission Control Protocol. both the protocol and software that ensure that data sent over
the Net arrive in the correct order.
TCP/IP
Short for Transmission Control Protocol/Internet Protocol. A group of protocols that specify how
computers communicate over the Internet. All computers on the Internet need TCP/IP software.
Telnet
An Internet command that allows your computer to directly connect and interact with remote computers,
often through a text-based 'terminal' environment. Often involves the need for passwords and access
information.
Unix
A computer operating system developed by AT&T Bell Labs and used to develop the Internet. It is no
longer the sole operating system used to run servers.
Upload
Transferring a file or files from the user's computer to a remote computer.
URL
Short for Uniform Resource Locator. A string of characters used to uniquely identify a page of information
on the WWW. This information is used by browser software to find other WWW, FTP, telnet, gopher, etc.
sites on the Internet.
Usenet
A group of computers that exchange network news information.
Veronica
An Internet tool that allows you to search by keyword through gopher titles and directories.
WAIS
Short for Wide Area Information Server. An internet search service that locates documents containing a
keyword or phrase.
WAN
Stands for Wide Area Network. A network of computers that covers a large geographical distance.
Whois
An Internet database that provides information on a person or an organization.
WWW
Stands for World Wide Web. A very popular Internet service that organizes information using a hypertext
and hypermedia system of linking documents, FTP sites, gopher sites, WAIS, and telnet.

CD-ROM GLOSSARY

A-D Conversion

    Analog to digital conversion, also known as modulation, involves special chips to convert analog
    signals to digital strings, or vice-versa. A-D conversion is necessary to send computer data through
    telephone lines, to produce digital audio, to have computerized telecommunications, to display data
    on analog displays, and so on.

A-Time

    Absolute Time is used to access sectors of data from the CD- ROM, identifying or addressing them
    from the beginning of the disc, using the drive's internal clock (min:sec:sector). It allows access of
    random amounts of data, such as video and audio segments, especially if the disc will include more
    than 98 individual audio segments. In Mixed-Mode discs, since only 98 tracks of CD-DA are allowed,
    track access is not workable. A- Time access involves mapping the audio portions in the CD-ROM
    (start and stop of each) using time addresses (Min-Sec-Sector), mapped relative to the beginning of
    the disc. This requires special care in determining the 'offset'--the amount of time used by all the
    components of Track 1 (pregap, post gap, application, etc.). Track relative time, on the other hand,
    involves mapping the times relative to the beginning of its track--which is a much easier option, and
    widely used in Mixed-Mode discs.

Access Time
   Amount of time it takes a CD-ROM drive to find and display the requested information. Although
   specified widely, access times must be used with care because there is no measuring standard. It is
   generally regarded to include radial positioning time (the head moves to the appropriate track), plus
   settling time (stops vibration), plus latency (wait for beginning of block with the wanted data)--all
   which take much more time than the final read and display step. The faster hard disk drives claim
   access speeds of 12 milliseconds or even lower, while the faster CD-ROM drives claim access
   speeds about 150 milliseconds.

Adapter Cards

   In computers, adapter cards (a.k.a. controller cards, expansion cards, interface cards, etc.) are small
   panels installed or plugged into slots of the main data bus, or bus extensions such as Local Bus.
   They are also necessary for networking computers. The cards 'adapt' the flow of data and instructions
   between the CPU and the device (peripheral), thus enhancing the computer's capabilities (memory
   expansion, fax- modem, advanced graphics, sound, I/O expansion, processor upgrades, etc.).

ADPCM

   Adaptive Differential Pulse Code Modulation is an audio encoding procedure (often referred to as
   compression algorithm) that takes about half the space of standard PCM, and involves different
   sampling rates and bits per sample, algorithms and chips to produce up to 20 hours of Level C,
   monaural audio in one CD. 'Differential' (often called 'Delta') refers to the way the algorithms
   determine and record only the differences between one signal and the next, using 4-bit numbers--
   thus reducing the total length of code. It is implemented with interleaving in CD-I and CD-ROM-XA
   applications.

Analog Signal

   A continuous signal that reflects the variation in the phenomenon being measured or represented,
   such as voice, temperature, pressure, intensity of light, electrical flows, etc. To be used in computers,
   analog signals, such as those in communications, must first be modulated into digital code.

Application

   In computer circles, it is a complete package of software and data designed to work in a particular
   computing platform. Main applications today involve wordprocessor, spreadsheet, database, desktop
   publishing (DTP), reference works, games, graphics, multimedia products, etc.

ASCII

   The American Standard Code for Interchange of Information, better known as the ASCII ('askey')
   character set, is the binary, 7-bit, 128-character set implemented as the standard in communications,
   and in mini and microcomputers. Because data is transferred as bytes, ASCII codes are added an
   eight bit (generally a 1-bit) to make up the standard eight-bit byte. This eighth bit is generally used as
   a parity bit.

ASPI

   Advanced SCSI Programming Interface is, essentially, a driver that helps the operating system deal
   with SCSI devices, such as CD-Recordable drives, by configuring it appropriately (dealing with the
   bus, ports, DMA channels, interrupts, other SCSI devices, etc.). ASPI is loaded by the CONFIG.SYS,
   and there are versions for various bus architectures.

Audio

   Until recently, audio signals have always been recorded and played back as analog signals. In
   computer circles, audio refers to files of digital (binary) codes that are produced by converting analog
   signals to digital audio. The quality of digital audio depends on the sampling rate and the sample size.
Average Access Time

      Average time, in milliseconds, it takes for a CD-ROM drive to complete a request to read task--the
      word to note here is 'average.' Some manufacturers specify their 1/3 stroke access time, and others
      specify random access time (also referred to as random seek time), or a combination of them--reason
      why using access times for comparisons should not be considered reliable and sufficient.

Bandwidth

      Originally a range of frequencies, in current computer circles it describes the capacity or amount of
      traffic (data, voice, video, etc) per unit of time. Mbits/second prevails in computer communications,
      while MBytes/second are used in most other computer applications. Some of the new microcomputer
      buses and local buses have bandwidths of up to 132 MBytes/sec. The first CD-ROM drives had a
      transfer rate of 150 Kbytes/second.

Binary code

      Computers are based on binary code; binary digits (bits), 0s and 1s that form bytes and files.
      Information is stored in binary files, in specific formats. Optical devices, such as CD-ROM, involve
      physical 'pits' and 'lands' on the coded track of the disc. But, in the end, they are decoded into 1s and
      0s of files that can be used by the computer.

Birefringence

      In CDs and other optical discs, it means double refractive ability. It is caused mainly by improper
      cooling of the substrate during the injection-molding process. In optical applications, however,
      birefringence is obviously unwanted, since it interferes with the read function. Users, however, can
      not determine that it is birefringence that is causing read errors or poor performance of their CD-ROM
      applications--it is detected by special equipment and tests.

Bit

      A compressed form of 'binary digit.' Therefore, a bit can be a 1 or a 0. A standard byte has eight bits
      (256 possibilities). Bits are used mostly when dealing with bandwidth rates (bits/sec), graphics
      resolutions, and related topics. Bytes are used when talking about data and files in general.

BLER

      Block Error Rates indicate the number of blocks that contain erroneous bytes (error bursts) during a
      read from the CD-ROM. BLERs also serve to gage effectiveness of mastering, replication, and CD-R
      encoding processes. Analysis of BLERs require understanding the basic Reed-Solomon error
      correction code, and the Cross-Interleaved Reed Solomon Code (CIRC)--which are basic for the first
      two layers of error detection and correction in CDs. An average BLER of less than 220 is considered
      within the specifications.

Block

      Unlike the blocks used in regular magnetic storage devices, in ISO 9660 optical discs, logical blocks
      are subdivisions of the sectors in the track. But, in most applications, the logical block is considered to
      be the same size as the user data area of the sector. This option has led to the common notion that,
      in CD-ROM, blocks and sectors are the same thing--which is obviously not true for all cases.

Blue Book

      This draft of the technical specifications of a High Density CD (HDCD), proposed by the Optical Disc
      Corporation (ODC), was submitted to the International Electrotechnical Commission (IEC) for
      adoption as a standard. It mentions the use of a new higher definition red laser to achieve a capacity
      of up to 3.3 gigabytes of user data in a CD. It apparently also claims that, using MPEG compression
   and a transfer rate of 3.3 Mbits/sec, the HDCD will be able to store a 135-minute full-length movie in
   one HDCD.

Blue Laser

   The development of a blue-light emitting diode (based on gallium nitride), in l993, in Japan, has
   opened the way for the production of a blue laser--which would essentially make possible the
   production of multi-Gigabyte optical discs. Some analysts observe that the technology is being tested
   in industrial and research applications, and expect that it will be implemented in the high stakes
   optical disc arena--by about 1998.

Boolean Search

   One of the various logical constructs (Boolean Operator, Logic, Modifier, etc.) named after George
   Boole (1815-65), a British mathematician who developed a system of algebraic logic that has been
   applied beneficially in various areas, including computer logic circuits and software applications. Most
   text search and retrieve software use the Boolean operators And, Or, Not, ButNot, etc. Boolean logic
   for database or numerical fields includes operators such as 'Less than,' 'More than,' 'Equal or More
   than,' 'Equal or Less than,' and so forth. With the advent of powerful processors and affordable
   memory, there is interest in other logical systems that produce faster text searches, some quite
   sophisticated indeed, especially in large and very large textbases. Boolean searching, however,
   remains predominant.

Bootable CD

   Some operating systems recognize and can use an ISO file structure, and therefore the CD can be
   configured with a boot record descriptor and operating system files (boot file), so the PC can boot
   from it--as some CDTV systems do. But, the Microsoft CD-ROM Extensions do not recognize the
   boot record descriptor in the CD, so MS-DOS PCs can not boot from it. As an alternative, in 1995,
   IBM and Phoenix Technologies announced an open Bootable CD-ROM format specification that
   would allow placing bootable images of floppies or hard disks on the CD-ROM, and a bootable CD-
   ROM BIOS in the system. To boot-up, the CD-ROM BIOS allows the system to read the
   preconfigured 'boot image' and proceed with the rest of the configuration. It was expected that
   applications with special configurations, games, multimedia applications and others will use the
   'bootable CD' option, but there is no clear evidence of that yet.

Buffer

   A usually small amount memory, directly available to the CPU, which holds momentarily either
   instructions or other information for it--not to be confused with memory cache. Buffers are used to
   overcome factors that affect direct access of instructions or data to the CPU; such as speed
   differences, interface delays, and other variations between a device and the CPU.

Bundling

   The practice of selling hardware or software, with additional items that, supposedly, do not add to the
   total price. Initially, minor software products were bundled with PCs and some peripherals. Recently,
   DOS, Windows, Modems, speaker sets, and especially CD-ROMs and Multimedia applications of
   various types are bundled with hardware and major software packages. This practice, however, has
   helped the growth of CD-ROM.

Bus

   In computers, a bus is the main or continuous channel of electrical connection between the CPU, the
   system memory (RAM), and the peripheral devices.

Byte
     Bytes are strings of bits, operated upon as a unit. Until recently, PCs were designed to use 8-bit
     bytes. The 128 characters of the ASCII character set are represented by 8-bit bytes, (seven plus a
     parity bit--thus only 128 characters). Bytes are also basic for the Hex and Octal notation used in
     computer programming. PCs measure file lengths and storage in bytes. Current PCs are
     implementing 32-bit buses, with 16 and 32-bit processors (which means they can handle data and
     instructions in strings of those lengths). For encoding CD-ROM discs, the magnetic 8-bit byte is
     modulated to the 14-bit optical byte.

Caddy

     A 'caddy' is a special plastic case that holds and protects the CD during operation--especially when
     the drive is mounted on its side. Caddies are not used for shipping. For WORM and Erasable media,
     they are called cartridges--probably because they do not allow extraction of the disc itself.

Capacity

     In general, the term capacity refers to the capacity of a CD, in megabytes of user data. Currently,
     there are CD-ROM media that can hold 63 or 74 minutes of data (74 min. is the maximum designed
     capacity). Before, because of equipment and other considerations, CD-Audio and CD-ROM did not
     use the outer area of the disc, and 60 to 63-minute discs were the rule. Today, because current
     equipment can encode and drives can read the outer area of the disc, 74-minute discs are common.
     The capacity of the disc, in bytes, is the number of user bytes per block, times 75 blocks per second,
     times the total time recorded in the disc. Furthermore, the total, in Megabytes, will depend on the
     definition of Megabyte. Using 2(exp 20), or 1,048,576, we will arrive to the figure of 527 MBytes for a
     60 minute CD-ROM. Obviously, this figure will be much higher for a 74-minute CD- ROM. Moreover,
     with multimedia CD-ROMs, all figures of capacity have to take into consideration the different
     amounts of user data in the blocks used for audio, video, and text. It is therefore possible to produce
     a 74-minute disc, Mode 2 (video, 2336 user bytes per sector), with about 778 million bytes, or about
     741 Megabytes of user data in it--and still remain within the ISO 9660 specifications. Users must be
     aware, therefore, of all these variables when dealing with disc capacities.

CCITT

     The International Consultative Committee for Telegraphy and Telephony, established by the United
     Nations within the International Telecommunications Union (ITU), is based in Europe, and
     recommends worldwide telegraph and telephone (including fax) transmission standards.

CD

     The Compact Disc was developed by Philips and Sony, and was first implemented commercially for
     storing digital audio data (CD-Digital Audio). The physical specifications for the 12cm disc, since
     known as CD, were issued in the now famous Red Book. The CD is made up of a polycarbonate
     substrate, a thin reflective metallic layer (the mirror-like is aluminum), and a lacquer coating. The
     encoded data track is a spiral track of about 2.2 microns wide, with the pits making a central band 0.6
     microns wide. The encoded track is made up of sectors (sometimes erroneously named blocks).
     Essentially, any other size of optical disc is not a CD.

CD-Bridge Disc

     A Bridge disc is defined as a CD-ROM XA disc that includes Mode 2 user data that can be played
     with a CD-I player. Additional codes in the CD-ROM XA tracks allow the output to be shown on a TV
     screen (CD-I players), and on a computer monitor (with CD-ROM XA players). The specifications for
     the CD-Bridge disc are known as the White Book.

CD-Digital Audio
   Philips and Sony developed the necessary technology for storing digital audio signals on a Compact
   Disc and, in 1982, introduced the CD-Digital Audio. This new product was based on the now famous
   Red Book (1981)--which specified the physical structures for the track and sectors in the disc. CD-
   Digital Audio was implemented to hold about 60 minutes of audio data, in up to 99 tracks (songs) at a
   sampling rate of 44.1 KHz and a sample size of 16 bits, to produce high quality stereo sound--thus
   revolutionizing sound quality reproduction. The success of CD-Digital Audio has been key for the
   growth and success of CD-ROM and other CD implementations.

CD-I

   Compact Disc-Interactive was developed by Philips and Sony, who issued the specifications in 1986,
   in what is known as the Green Book. CD-I employs the CD, with a sector structure similar to CD-
   ROM-XA, and addresses issues of synchronization to implement interleaved data, compressed audio,
   still frames and full-motion video files, complying with the ISO 9660. CD-I was advertised as the
   upcoming interactive multimedia platform, but current CD-I products aim mainly towards business and
   education multimedia interactive applications. A mayor drawback was that CD-I uses proprietary
   hardware, operating system (OS9), and data compression solutions--including MPEG-1. The
   keyboard-less CD-I drives range from the basic player to the professional set, and can display to
   NTSC and PAL monitors. CD-I players can play CD- Audio and Bridge discs (Kodak Photo CDs, and
   Video CD) compliant with the White Book. PCs, with a special add-on board, can read CD-I discs.

CD-I Ready

   A CD-I Ready disc is defined as a CD-Audio disc that includes a CD-I application, and can be played
   with a modified CD-I player. It involves extending the pre-gap space of CD-Audio, and including in it
   data that only the CD-I player can recognize and use. This additional functionality allows CD-I to
   present additional information about its contents.

CD-Recordable

   CD-Recordable technology allows production of CD-ROMs on the desktop ('one-offs'). It requires a
   CD-R recorder, appropriate software, a PC, and appropriate media. The reduction of prices for this
   hardware and software, and their ease of use, have helped the growth of CD-ROM production in-
   house. CD-Recordable involves a special CD, the 'one-off' blank, very different from the mass-
   reproduced or 'hot-pressed' CDs. It is sold pregrooved, in 63 or 74 minute capacities, and it involves a
   layered structure--with a sensitive chemical recording layer, almost always with a gold reflective layer,
   and ready for a CD- Recordable drive. Once recorded, the CD-Recordable discs (one- offs) perform
   in the same way as the mass-reproduced CDs.

CD-RDx

   The CD-ROM Read-Only Data Exchange Standard, developed by the CIA, Intelligence Community
   Staff, aimed to achieve "...system and software interoperability for CD-ROMs," which was further
   explained as the "...ability to publish a single integrated collection of data and indexes on a CD-ROM
   disc and make it accessible on any ISO 9660-compatible computer system." A final draft circulated in
   early l993.

CD-ROM

   The Compact Disc-Read Only Memory is the standard 12cm CD formatted according to the ISO
   9660. Although the physical characteristics and track structure of a CD-ROM are the same as that of
   CD-Audio, a CD-ROM is used to store computer data (text, graphics). It also involves additional error
   detection and correction--as specified in the Yellow Book. The logical volume and file structure of CD-
   ROM, specified in the ISO 9660 allows it to be used in the computer arena. Therefore, a CD with
   computer data that is not structured according to the ISO 9660 is not a standard CD-ROM.

CD-ROM Drives
   The growth of the industry is reflected in the types of CD- ROM drives offered today. The original
   drives had a transfer rate of 150 KBytes/second, but recent drives offer double, quadruple and even
   higher transfer rates--and are known as 2X, 6X, and so on. Some early CD-ROM drives could not
   handle audio tracks; current drives can handle audio tracks and, for multimedia, have connections for
   the sound card. Some recent drives are also XA-ready, and/or Photo-CD ready, with or without
   multiple session capability. The choices available demands users to consider carefully their true
   needs.

CD-ROM Extensions

   The MS-DOS operating system (just as other operating systems) was developed before optical
   technology became available for the PC platform. Therefore, Microsoft had to add appropriate
   capabilities to MS-DOS, so that the PC could acknowledge an ISO- compliant CD-ROM as another
   storage device. The program, MSCDEX.EXE, is known as CD-ROM Extensions, and is loaded by the
   Autoexec.Bat. Apple has Apple Extensions for its Hierarchical File System, and Commodore has
   CDFS extensions for CDTV.

CD-ROM Tower

   This is a configuration of CD-ROM drives in one box, known as a tower. CD-ROM towers are usually
   implemented in networks, usually with an appropriate CD-ROM server. They work well in busy
   multiuser environments because all the drives in the tower are accessible at all times, while
   jukeboxes access only one disc (or a few discs) at a time. Recently, some manufacturers have
   introduced tower models with CD-Recordable units, and LAN-ready configurations.

CD-ROM XA

   CD-ROM Extended Architecture, developed by Sony, Philips and Microsoft, involves extensions to
   the Yellow Book, and defines two new types of sector (CD-ROM Mode 2 sectors are 'extended' into
   CD-ROM XA Form 1 and Form 2 sectors). The new CD-ROM XA sectors are used for data, graphics,
   video, and compressed audio, in an interleaved scheme (CD-I structure)--making it possible to read
   and display jointly text, graphics and audio files of various sample sizes, up to 20 hours of 4-bit
   monaural sound. Kodak's Photo CD for example, uses XA tracks, and it can therefore be read by an
   XA drive.

CD-Singles

   Since 1991, the 8cm music 'CD-singles' were popular in Japan. Formatted under ISO 9660, the 8cm
   disc can hold up to 200 KB of data and be played by the Sony Data Discman. Some CD-ROM-XA
   applications have been ported to 8cm discs. This 8cmm disc should not be confused with the Sony
   8cm MiniDisc, which is an M- O rewritable disc (Orange Book).

CDTV

   Commodore Dynamic Total Vision, released in 1991, involved CD-ROM for multimedia applications
   for Commodore PCs that displayed to a TV monitor. Its particular file system (CDFS) is set to use the
   ISO 9660 (Interchange Level 2) file format. But, CDTV discs that implement Interchange Level 2
   (allowing smaller logical blocks, different filename lengths and character set conventions) are
   incompatible with the IBM-compatible platform. CDTV also is capable of booting from the CD. For
   various reasons, CDTV weakened as Commodore lost market share in the US-- though they seem to
   be holding on in some foreign markets.

CD-V

   Compact Disc-Video is an implementation of the CD to store full motion video (analog, about 5-6
   minutes) and CD-Audio tracks (about 20 minutes). CD-V requires a special CD-V drive, and is used
   mostly in the commercial video production arena. Because digital video is implemented in various
   platforms, there are video discs in 20cm (8in) and 30cm (12in) formats as well--but these are not
   CDs. CD-V should not be confused with the upcoming Digital Video Disc, nor with Video CD
   introduced by Panasonic.

CD-WO

   Compact Disc-Write Once is rather recent, but is often confused with the older WORM (Write Once
   Read Many) technology. More appropriately, CD-WO is defined by the Orange Book, Part 2 (1990). It
   involves the 12cm CD, with a recordable layer that can be written to, but not erased and rewritten.
   Therefore, once the tracks have been encoded, a Table of Contents is created and placed in the
   appropriate place (the track's Lead-in). CD-ROM players use that TOC to read the contents. A CD-
   WO Hybrid disc involves an area where Read-Only files can be placed, and the rest of the disc is the
   W-O area, which can be written to in one or more sessions (each session creates its own Table of
   Contents). Multi-session discs need multi-session capable drives, such as the Kodak Photo CD drive
   and the newer multi-session ready drives. The older WORM technology remained mostly proprietary
   and uses optical media of various sizes.

Channel Bits

   The optical bytes, after the eight-to-fourteen modulation, are recorded in channel bits--which produce
   the pits and lands on the data track. In another context, channel bits refer to the bits that make up
   each of the 98 Control Bytes included in each sector. Those channel bits are named P, Q, R, S, T, U,
   V, and W, and each of them represents a subcode channel, and include important information for
   timing, types of information, tracking, etc.

CIRC

   Cross-Interleaved Reed-Solomon Code is used in compact discs for the first two levels of error
   detection and correction. CIRC in CD-Audio provides an integrity of one erroneous byte in a gigabyte
   (two CDs). The additional and more sophisticated third level 'layered' error detection and correction in
   CD-ROM claims an integrity of one byte in 2,000 CD-ROMs.

Cladding

   Special material used to line or cover an optical fiber, to reflect and confine the light waves to the
   core.

CMP

   A joint Committee on Multimedia Technology formed by the Interactive Multimedia Association (IMA)
   and the Society of Motion Picture and Television Engineers (SMPTE) to deal with issues about
   multimedia, produce technical papers, propose standards and distribution guidelines, and promote
   product interchange and interoperability in the multimedia industry.

COLD Technology

   COLD is the industry term for Computer Output to Laser Disk. The term COLD reflects the fact that
   optical disks (or laser disks) were the archival media utilized in the early systems. Current optical
   technology, however, offers CD-ROM-based archival subsystems, RAID subsystems, various optical
   disc jukeboxes or autochanger systems, and others--with an assortment of software for their use.
   Most people are familiar with COM (Computer Output to Microfiche), which is being replaced by
   COLD technology. But, in the near future of the imaging industry, COLD may be replaced by COAR
   (Computer Output Archival and Retrieval) which is more representative of the current archival and
   search and retrieve technologies--which will add more value and broad accessibility to applications
   based on computer output.

Compression
   The large file size of audio, graphics and video files for CD-ROM applications forced development of
   hardware and software compression-decompression procedures. While most compression solutions
   are designed with specific types of files in mind (text, audio, video, graphics, etc.), recent
   compression solutions are quite sophisticated, and some even aim to compress the entire contents of
   a CD-ROM before mastering and, decompress when accessed--'on-the-fly'. The compression-
   decompression markets will certainly remain active for the foreseeable future.

Connectors

   These are the physical cables, receptacles and plugs used to connect devices in and to a computer.
   Although they are designed for specific types of connection (serial, parallel, SCSI-1, SCSI-2, SCSI-
   SCA, etc.), most CD-ROM and other optical devices use different connectors and cables--depending
   on the manufacturer, operating system, and even model.

Constant Angular Velocity (CAV) and Constant Linear Velocity (CLV)

   Magnetic and optical storage drives can rotate with constant angular velocity (CAV), or constant
   linear velocity (CLV). CAV, used by magnetic drives (and record players), is measured in RPM, and
   means that the read head sweeps the same angle, for the same amount of time, at all radii. CLV,
   used in CD-ROM, allows the head to read the same length of track at all times and radii (1.3
   meters/sec), which requires that the disc spin slower as the head moves to the outer edge of the disc.
   A CD-ROM spins from 539 RPM at the inner edge, to 210 RPM at the outer edge.

Control Bytes

   The CD-ROM physical block structure specifies a data user area of 2048 bytes and other sets of
   bytes, to make a full sector--including the 98 control bytes. These control bytes, with sub-channels at
   the bit level, are specified in the Red Book. They are key for much of the functionality of CD
   implementations.

Convergence

   A term in the industry that tries to explain the pressures on optical technology, mainly CD-ROM
   development, to bridge the gap between computer users and television viewers. The aim is,
   ostensibly, to produce multimedia applications that would serve and satisfy the needs of both groups,
   with one hardware device. To some, the term even includes conjunction with the Internet and other
   network services.

Conversion

   Generally used to mean conversion of computer files from one system to another, or from one format
   to another (DOS to Mac, EBCDIC to ASCII, PCX to TIFF, and so on). In some cases, conversion is
   used to mean putting the information on another media--as in digitizing information that is on paper, in
   microfiche, video, etc. Conversion is usually a key and expensive part of the data preparation
   process. In fact, the growth of the conversion industry is a reliable reflection of the growth of the CD-
   ROM, optical imaging, and multimedia industries.

CPU

   The Central Processing Unit, or processor chip, is the 'brains' of the computer. For floating point
   computations, the CPU employs the co-processor chip--if there is one present on the motherboard.
   Current CPUs generally include a co-processor chip. Database, spreadsheet, CAD-CAM and other
   vector graphics applications, and most software decompression algorithms benefit from the use of a
   co-processor. That is why some multimedia applications work smoother with a fast CPU and a co-
   processor. The MPC Level 2 requirements, however, include only a 486SX chip (no co-processor),
   4MBytes of RAM, and a 2X drive as a minimum-- which is not adequate for most current multimedia
   releases.
CRC

   Cyclic Redundancy Check is a method for detecting errors in data transfers. A special polynomial
   algorithm produces and uses a coefficient and a remainder (usually 16 or 32 bits long) to check if the
   transmission proceeded without problems. CRC values change even if only one bit in the file
   changed--which makes CRC extremely reliable for checking integrity of files transmitted between
   computers.

CRT

   Originally, somewhat appropriately, computer monitor screens were dubbed CRTs, because the
   Cathode Ray Tube was its biggest component. Current CRTs offer ever-increasing resolutions and
   sophistication. Flat display technology, however, does not employ the CRT and is becoming a
   competitor because it is no longer used only in portable or notebook computers.

Daisy Chain

   Peripheral devices connected serially are said to be 'daisy chained,'--as in SCSI configurations. While
   a SCSI card uses only one slot in the bus, all the devices in the daisy chain are available, because
   each has a specific address, and the devices in the chain respond only to the instructions addressed
   to them.

DAT

   Digital Audio Tape, generally high-quality 4mm magnetic tape in a cassette, with capacities up to over
   1 Gigabyte, that has been used in the computer arena mainly as an archival and back-up medium.
   For CD-ROM, it is used as a transfer medium.

Data

   Plural of datum, in the sciences, refers to sets of figures, measurements, expressions, etc. that, when
   expressed in a defined framework, acquire meaning that makes then information. For example, 45,
   35, 75, are essentially meaningless figures (data); but, when expressed in terms of degrees
   Fahrenheit, they mean specific levels of temperature (information). In computer terminology,
   however, data generally is used to mean files with user information.

Data Area

   This is the space in the track, specified by the ISO 9660 specifically for the sectors with user data. It
   is recorded after the System Area, and is followed by the Lead out.

Data Discman

   A Sony portable drive that plays Sony's 8cm discs, media that was used initially for audio 'CD-
   singles.' Since l990, the Data Discman plays CDs formatted according to the ISO 9660--which can
   hold up to 200 Kb of information. More recent implementations include compressed audio--using the
   CD-ROM-XA format. For some reason, the DataDiscman has not become popular in the US.

Database

   In traditional computing, databases are structured collections of fielded data sets that can be updated,
   manipulated, indexed and used as sources of appropriate information. With the advent of large
   collections of text, graphics, and other types of information incorporated in single applications, the
   concepts of database, media and information are expanding.

Data Preparation
    This is usually the most time-consuming and also the most expensive part of the application
    production process. Since, with rare exceptions, all the necessary data is usually in a mix of media,
    file formats, databases and others, it takes a lot of preparation and work to get them in the shape and
    formats appropriate for use in the CD-ROM application. Therefore, data preparation must be a
    carefully planned step in the process.

Data Transfer Rate

    This is, essentially, the reading speed of the original CD- ROM drives (150 kb/sec). Since the
    computer can handle data at higher speeds, manufacturers are now offering 2X, 4X, 6X and even
    higher speed drives. Some trade magazines are already previewing 12X drives.

DBMS

    A Database Management System generally involves policies about the coordination of data entry,
    database operations, output, access, and information security in an organization. Systems vary in
    size and sophistication, and there are many appropriate software DBMS front-ends in all platforms,
    and more and more DBMS include CD-ROM as their archival medium.

DCT

    Discrete Cosine Transform is a mathematical algorithm used in compression/decompression
    programs, especially for color graphics and motion video--such as in JPEG and MPEG. MPEG-1
    uses DCT for intraframe compression. MPEG's high rates of compression, however, are due mainly
    to its interframe compression.

Demodulation

    In data communications, transmission through telephone lines involves modulation at one end, and
    demodulation at the other end. For this purpose, computers use the modem.

Digital

    Generally contrasted to analog, digital refers to the use of digits (0-9), in specific code schemes. The
    binary coding scheme uses 1s and 0s, and is the basis for digital computers. Although analog
    computers were developed, binary processors rule technology--from cheap consumer items to Cray
    supercomputers.

Digital Audio

    The Red Book specifies the quality of digital audio to be encoded in a CD-Digital Audio product,
    although that quality is also used in other platforms. The sound is sampled at 44.1KHz, and quantized
    at 16 bits/sample for high quality stereo sound (65,536 values). Sound of different quality, even if it is
    placed in a CD, is not Red Book Digital Audio.

Digitization

    Digitization generally refers to the process of translating or converting data and information (in paper,
    analog sound tracks, graphics, etc..) into binary coded files for use in computers. Text can be
    keystroked or OCR'd, graphics are scanned, video is digitized, sound is sampled and quantized, and
    so on. Digitization is the heart of the new conversion industry.

Disc Read Head

    Storage drives (magnetic and optical) have a head or heads that float over the recorded area to read
    and write. Obviously, CD-ROM drives have only a read head, which involves a low-intensity red laser
    diode (a.k.a. infrared laser diode), lenses that focus the laser on the track, and others that redirect the
    reflections to one of the photodiodes for appropriate decoding. Some Write-Once and Rewritable
   optical drives involve two heads (to write and read), while other drives, including CD-Recordable, use
   only one head to do both--using a high-intensity blue argon laser for the write function. For mass
   replication of CD-Audio and CD-ROM discs, the glass master is produced by encoders that have
   special recording heads.

Disk Sector

   In magnetic disks, formatting, provides a geography of the platters; which are divided into concentric
   circles, and these circles are further subdivided into sectors. Although sectors vary in size depending
   on their position in the disk, they have a specific capacity in bytes. This sectored framework is found
   in constant angular velocity (CAV) drives, and is compatible with the FAT used in PCs. When
   discussing optical discs (with c), 'sector' is used to refer to discrete amounts of data with a specific
   layout or structure along the track.

DMA

   Direct Memory Access takes place when an input/output device (hardware), or an application
   (software), issues calls or writes directly to system memory--while the CPU, essentially, lets that
   happen. MS-DOS implements a table of DMA channels for that purpose.

DOS

   Disk Operating Systems pertain to microcomputers. In fact, early microcomputers operated with one
   of various operating systems. When IBM chose the operating system developed by Microsoft, which
   could handle hard and floppy disks, it was called Microsoft Disk Operating System. Since then, all
   operating systems for microcomputers, especially IBM-compatibles, are called DOS (MS-DOS, IBM-
   DOS, Dr. DOS, 4-DOS, etc.).

Double-layer CD

   Recently, it refers to the technology developed by 3M, which allows production of a CD with two
   recordable layers on the same side. To read it, the single head shifts the laser's focal length
   appropriately. Double-layer CDs will become common, since the industry agreed to make it part of the
   specifications for the DVD format.

Double Density CD

   This name has been applied to the CD format proposed by Nimbus Technology and Engineering
   (1994). It claims to encode more than two hours of a CD, by increasing the number of tracks per inch.
   Double density, and more, was also demonstrated by Optical Disc Corporation (ODC), which
   proposed its own High Density CD specifications in late 1993. These efforts, however, have not
   attracted the attention that Philips, Sony, Matshushita and the other established players received for
   their specifications that led to the industry's Digital Video Disc.

DRAW

   Direct Read After Write was an expression originally used to differentiate W-O and Rewritable from
   CD-ROM technology. DRAW implied that W-O and Rewritable disks could be accessed or read
   immediately after being written to, while CD-ROM could not--because, by design, it had to be mass
   replicated first.

Driver

   In computers, driver refers to a device driver, which is software that, under CPU control, implements
   device I/O functions or other functionality (video, sharing, graphics, printer, mouse, etc.).

DSP
      Digital Signal Processors are specialized processor chips used for diverse functions, especially in
      modems, sound boards and serial ports.

DVI

      Digital Video Interactive, developed by Intel and IBM, is conceptually similar to CD-I. DV-I, however,
      emphasizes a compression scheme that employs proprietary chip sets (for compression and
      decompression of audio and video) that require add-on boards. These DV-I boards display VHS
      quality full-motion video. But, the surge of applications implementing the MPEG standard has affected
      the growth of DVI. It is, however, still used in public information, education and training.

DVD

      Digital Video Disc is an upcoming product. Nimbus and Optical Disc Corporations (ODC) already
      showed their capabilities to master double density, and Philips quad-density CDs. The emphasis
      turned, however, on the Digital Video Disc. One camp, headed by Sony and Phillips, first promoted
      the MultiMedia CD, and then the High Density CD (HDCD,1994). The other camp, headed by Toshiba
      and Times-Warner, promoted the SuperDensity CD (SDCD) and changing the name, proposed the
      DVD (Jan95). The HDCD specifications included single and dual-layered, single and dual- sided CDs-
      -with corresponding capacities from 1.3 to 7.4 GB, and playing times from 47 to 270 minutes. The
      early DVD specifications included single and double-sided CDs, with capacities of 5 to 10 GB, and
      playing times from 135 to 270 minutes. It was understood that MPEG-1 was included. To keep within
      the traditions of the industry, these two camps, after the compulsory maneuvering, were helped in
      their decision to compromise on a single set of specifications for DVD. The announcement of the
      compromise specifications (Sep95) mentioned a double-layer single-sided CD with a capacity of
      4.7GB, the use of EFM+ signal modulation, and another version of the Reed-Solomon error detection
      and correction schemes. Most analysts thought the announcement satisfied the video industry's need
      for a disk with sufficient playing time for a full-length movie, compatible with MPEG-2, and backward
      compatible. There is, however, ample flexibility in the specifications for single-layer, and double-sided
      double-layer CDs, of varied capacities. Applications in DVD format are expected by mid-1996.

EBCDIC

      Extended Binary Coded Decimal Interchange Code, is an 8-bit, no parity, 256 character code (in
      several variations), used mainly in IBM mainframes and related platforms. Unlike the 'extended' ASCII
      character sets, EBCDIC variants are not standard. Conversion between EBCDIC and ASCII platforms
      is therefore not an automatic process.

EFM

      Eight to Fourteen Modulation is used during encoding, because the 8-bit 'magnetic' byte has to be
      modulated to a 14-bit 'optical' byte. Technically, this modulation is necessary to allow encoding of two
      consecutive 1s--which would be impossible with the scheme of pits and lands using 8-bit bytes (1s
      and 0s). In fact, the changes in reflectivity (as the laser light moves along the sequence of pits and
      lands) are coded as 1 channel bits. Two consecutive 1s are therefore not possible. Moreover, the
      'lands' in between the 1s are represented by 0 channel bits, and the number of 0s represent the run-
      length. The bits in an optical byte are known as 'channel bits' to avoid confusion, and because they
      are transferred to the controller board through a specific channel. Furthermore, the fourteen-bit optical
      byte is provided three additional channel bits, known as merging bits--to eliminate transition conflicts
      between consecutive optical bytes. During the read process, the interface card demodulates the 14-
      bit optical code to the 8-bit code used by the computer--and all channel bit-level modulation and
      processing remain transparent to the user.

EISA Bus

      The Extended ISA Bus, was introduced by PC manufacturers as their alternative to the IBM MCA
      bus. It is also a 32-bit bus, supports high speed data transfers, allows post-installation configuration of
   adapter cards, and can access higher amounts of system RAM. Unlike the ISA bus, the EISA bus
   does not support 8- bit adapter cards. PCI buses with Pentium CPUs seem to have hurt EISA
   standings.

Electroforming

   In jewelry, it is used to lay fine gold or silver surfaces on complicated pieces, or on extremely fine
   shapes and surface configurations, because the electromagnetic field sets the fine metallic particles
   in place. In the CD industry, where the pits in the glass master are measured in tenths of microns,
   electroforming is used to 'form' the initial metallic (nickel) mold that is used to produce the stampers
   for the injection molding machines.

Encoding

   In the computer arena, programmers and users see and work with higher level languages, but the
   processors deal with machine languages and binary code. To use optical technology, it was
   necessary to develop an encoding scheme that would produce the 8- bit computer bytes, while using
   the pits and lands produced by the laser on the disc surface. The resulting optical encoding scheme,
   uses a 14-bit byte modulated from the 8-bit byte--in which the 1s represent the transitions between
   lands and pits, and the 0s represent the run-lengths. The mastering machines do the encoding, and
   the controller card of the drive does all the decoding.

EPROM

   Erasable Programmable Read Only Memory chips are being used increasingly more. Until recently,
   all important hardware configuration, BIOS, and other defined information was stored in ROM chips--
   to prevent accidental erasures or modifications. But, with EPROMs, knowledgeable users can
   reprogram ('burn') the code in those chips as deemed necessary. EPROMs are also used to provide
   firmware for higher end hardware configurations.

Erasable

   In optical technology, erasable generally referred to optical drives that allow the user to write and
   erase at will--just as with magnetic hard drives. Currently, however, the preferred term is rewritable,
   as in magneto-optical rewritable technology.

Error Detection Codes (EDCs) and Error Correction Codes (ECCs)

   For data integrity, CD-Audio includes two levels of CIRC error detection and correction, as specified
   in the Red Book. Because computer data requires higher that audio levels of integrity, the Yellow
   Book specified a third level of such codes in each CD-ROM sector (4 bytes EDC and 276 bytes
   ECC). This third level involves a layered error detection and correction scheme, and is sometimes
   referred to as the Block Error Correction codes.

Exabyte

   Originally a brand name, it is used commonly to refer to the high quality, 8mm wide, magnetic tape
   (designed for video), in special cassettes, of capacities up to over 2 GBytes, currently used in the
   computer arena mainly as an archival medium, and in tape libraries--also manufactured by Exabyte.
   In CD-ROM, 8mm Exabyte tapes are used as a transfer medium.

Expansion Bus

   Because of the growth in computer devices, some users fill all available slots in the main bus.
   Expansion buses, some of them proprietary, as in the early 'luggables,' allow users to connect other
   controller cards and devices to the main bus.

Fielded database
   Some years ago, this phrase would have been considered redundant, since databases were
   composed of data in fields. But, since the advent of large collections of text, and since the noun
   textbase did not catch on, 'fielded databases' and 'fulltext databases' are widely used. Fielded
   databases are, essentially, those that do things with data in fields--the way dBase and others do.

Floptical Disk

   The name implies the physical nature of a floppy disc and optical technology, but the floptical disk is a
   magnetic disk. It uses optical technology only to align the head along the tracks, which are at a much
   higher density than regular floppy disks. That density accounts for its capacity--about 20 MBytes. But,
   floptical disks did not fare as first expected.

Foreign File Access

   The Apple operating system provides Foreign File Access to allow reading of CD-Audio and CD-ROM
   (ISO 9660 and HSF) discs. In a quite different option, ISO 9660 discs can be read by Apple
   computers that have the Apple Extensions for ISO 9660--which, essentially, make the CD-ROM look
   like an HFS-formatted disc.

Format

   In the computer arena, there are physical and logical formats for storage devices. Magnetic storage
   devices implement a physical structure (MFM, RLE, IDE, SCSI, etc.). A high level formatting program
   establishes its physical layout, and a low level format assigns logical identities and file allocation
   tables to all its partitions. CD-ROM discs use the physical format defined by the Red Book (which
   defines the size, tracking, sector contents, etc.). The standard logical format is defined by the ISO
   9660, the volume and file structure that was the key for the growth of CD-ROM.

Frame

   Commonly, frames imply the basic elements of display. Television, we say, displays 30 frames per
   second. In CD-ROM, however, a frame is not related to display. During mastering, the CD-ROM
   sector is subdivided into 98 frames, and the bytes in those frames are modulated from 8 to 14 bit
   structures. In fact, those new optical bytes are provided with three merging bits, to eliminate conflicts
   between bytes. The chain of bits thus produced are used by the encoder, to 'burn' the pits and leave
   the lands on the recording layer of the glass master. Nevertheless, all these things are done by the
   mastering equipment, and are transparent to the user.

Frankfurt Group

   A group of the industry's top firms met in Frankfurt, in 1991, and proposed an ISO 9660-compatible
   standard for multi- session recording--which was not part of the ISO 9660. They also supported the
   Rock Ridge Proposal, which deals with multi-platform volumes. The Frankfurt Group's proposal,
   published by ECMA as Working Paper TC 15, deals with logical specifications for the Orange Book,
   Part II (W-O). It establishes two types of file structures: Type 1 is compatible with other ISO 9660
   discs, and can be read by a standard drive. Type 2 allows 'incremental multi-session recording' in a
   CD-WO volume. Hybrid Discs include both types of file systems, but standard drives could only read
   the Type 1 area--but, more importantly, the Type 2 areas would allow recording applications that can
   be used by different operating systems or platforms. Approval was expected in late 1995, and new
   operating systems were expected to support the resulting standard.

Full-text Database

   Essentially, this is a large collection of textual information or documents--ready to be managed by a
   full-text retrieval software package. Therefore, a large collection of text files alone does not a full-text
   database make. If however, they are configured and indexed for software that can perform searches
   across all of them, and perform output functions, then and only then you have a full-text database.
Glass Master

      This product of the mastering process involves a large glass disc, duly prepared and coated with a
      recording layer--usually Photoresist. After recording, the glass master goes through a special
      chemical process (akin to development), and is then metallized. The metallized glass master, also
      referred to as the 'positive,' is submitted to electroforming, to produce the metallic (usually nickel)
      master--which is necessary for producing the stampers for the injection molding machines.

Green Book

      Published by Philips and Sony in l986, the Green Book uses the ISO 9660 to establish the block
      structure for CD-I, addressing problems of synchronization and use of file compression for multimedia
      applications (CD-Audio, other audio, data, graphics and video). Although it looks like a CD-ROM XA
      sector, a CD-I sector uses the area (8 bytes) left unused in the Yellow Book CD-ROM sector structure
      in a different way.

GUI

      Graphical User Interfaces are becoming predominant. Computer operating systems are designed to
      work, out of the box, implementing the command line (prompt), in the basic text mode screen (80x25
      for PCs and 80x24 for Unix terminals, etc.). But, the growth and popularity of graphical applications
      led to the implementation of graphical user interfaces. GUIs work in graphics mode; that is, they
      display everything on the screen as a graphic and, instead of the command line, they implement
      menus and other graphic objects that are operated with special keystrokes or a pointer device--the
      ubiquitous mouse. Microsoft Windows is the predominant graphical user interface in the IBM-
      compatible platform, and others predominate in the OS/2, UNIX, and other operating systems.

Hard Drives

      Originally known as Winchester drives, these magnetic storage devices have one or more non-
      removable solid platters--as opposed to the floppy-disk drives. Hard drives come in various types,
      different capacities and configurations--and are connected to the bus through a controller or interface
      card. There are removable hard drives, which allow removal of the component that contains the
      platters--a workable option for users with security concerns.

HDTV

      High Definition Television has been in use in Japan and Europe for some time. The US has been
      trying to convince all (especially the Japanese) to use the HDTV specifications developed by the US
      industry, thereby delaying implementation of HDTV in the US. Expectations were that the US may yet
      win the specifications contest.

Header

      In computer circles, headers meant a set number of bytes at the 'head' of the file--with information
      about the file, especially necessary when dealing with large numbers of files in tapes. In current PC
      usage, the term refers more often to headers of graphics files. A TIFF file, for example, can have
      extensive functionality because the TIFF header has broad features and flexibility. Graphics headers,
      however, can become problematic, because specifications about headers are rather liberal and too
      many developers include in the headers additional information useful to their applications. But, those
      efforts often cause problems when other applications try to use those files.

High Sierra Format

      The development of the High Sierra Format is part of the industry's interesting history. After the
      publication of the Yellow Book, facing the growth of CD-ROM applications in proprietary formats,
      representatives of the major firms in the industry met at the Del Webb's High Sierra Hotel and Casino,
      in Lake Tahoe, Nevada, to agree on basic specifications for a common logical format and file
      structure for CD-ROM. Soonafter, they published the "Working Paper for Information Processing:
      Volume and File Structure for CD-ROM Information Exchange (1986)," since known as the High
      Sierra Format (HSF). Their unprecedented effort proved to be key for the effective role of standards in
      the CD-ROM industry. And, to their credit, the ISO 9660 is essentially their Working Paper with some
      pertinent modifications and extensions. Today, only organizations that do not distribute their CD-ROM
      application beyond their organization are still producing HSF discs.

Hit

      In search and retrieve applications, hits refer to the matches or instances found by the software. Most
      applications remind the user to combine search parameters appropriately to generate efficient
      (narrowed down) searches and produce the most relevant results or matches.

Hollywood Digital Video Advisory Group

      A committee of representatives of the entertainment industry (Columbia, Disney, MCA/Universal,
      MGM, Paramount, Viacom, Warner Bros., et al.) that met in l994, and proposed their guidelines for a
      desired DVD product. Those guidelines were important for the compromises towards the final DVD
      specifications.

HPSB

      The High Performance Serial Bus, developed by the IEEE, specifies a no-loop bus that can connect
      up to 63 devices on a single bus. The base transfer rate is 100Mbits/sec, and highest expected
      transfer rate is 400Mbits/sec--to accommodate future devices and PCMCIA features. HPSB, as an
      interface between devices, does not specify its own packet protocol; it will use other protocols. ANSI
      is apparently adapting SCSI-3 specifications (command, transfer and control schemes) for its own
      specifications for use with the HPSB.

Hub

      This is the central hole of the optical disc. The spindle of the drive clamps the disc by this hub, which
      should fit rather precisely to provide reliable centering and eliminate flutter.

Hypercard

      Interface card and software for Macintosh computers, to use and produce multimedia applications.
      The software development tool in the recent version 2.3 includes text-to-speech (with Plain-talk
      software) and other up-to-date capabilities. Since Hypercard was bundled with the Macintosh, its
      users have been spared the problems of compatibility and upgradability of the multimedia kits and
      peripherals in the IBM-compatible world.

HyTime

      Hypermedia/Time-based Structured Language is an international standard (ISO/IEC 10744:1992) for
      an SGML-based set of semantic extensions to SGML. They help structure or represent hypertext and
      multimedia elements in SGML documents--recent proposed extensions involve maps, music scores
      and others. Promoters of HyTime aim to add multimedia functionality to SGML-based documents, in
      system-independent applications.

IDE Interface

      The Intelligent Device Electronics interface supports ISA, EISA or MCA buses, and is much smaller
      than the original disk controller cards. IDE hard drives include most of the circuitry that previously
      resided in the interface card. The growth of multimedia helped the growth of sound cards and of IDE
      controller cards that support CD-ROM drives.

Image
    After the application works as desired, in the PC, the data, retrieval software, indexes, interface, and
    other files are placed in the desired order--aiming for their most efficient location in the eventual CD-
    ROM. Usually, the application is tested at this stage. And, then, this collection of files, in appropriate
    block sizes, along with descriptors, etc., is written as a large file, to a transfer medium to be sent for
    premastering. That collection is therefore known as the 'CD-ROM image' or just 'image.' More
    precisely, an 'ISO image,' refers to the contents of a disc that will be premastered to an ISO 9660
    volume structure.

Imaging

    This relatively new term refers to the use of computers to work with graphics, as well as conversion of
    documents to computer usable graphics formats (generally TIFF or PCX format). The imaging
    hardware and software industries have been high growth industries these past years. In fact, the
    multimedia, archiving, online document management, and other arenas are certainly poised to keep it
    that way.

Implementation Levels

    The ISO 9660 specifies three Interchange Levels--which deal with file naming and their use by
    different operating systems. But, since some operating systems can not implement the interchange
    levels effectively, the ISO 9660 defines two levels of implementation. Implementation Level 1 allows
    producers to limit their implementation of the features of the chosen interchange level. Level 2
    specifies that all the features of the ISO 9660 interchange levels must be supported. In the IBM-
    compatible world, for example, because MSCDEX.EXE supports only Implementation Level 1, some
    features specified in the interchange levels are generally not used, and others are used with some
    limitations (path lengths, characters to be used in filenames, number of directory levels, and others).

Indeo Video

    This codec, introduced by Intel, supports high quality video (320x240) that is used in multimedia
    applications, and allows software-only playback with PCs with 486 or Pentium CPUs. It is also
    supported by Microsoft's Video for Windows and Apple's Quick Time--which also has a Windows
    version. Intel's Indeo supported vector quantization technology, but the recently introduced version
    3.2, Indeo VI (video interactive), is said to support a new hybrid wavelet-based technology. As with
    previous versions, developers can use Indeo VI royalty-free.

Indexing

    In CD-ROM, indexing involves assigning searchable 'addresses' within a track--which can be up to
    99. But, in data management, indexing involves creating sets or tables of pointers to the records or
    information in the database. With the new processors, complex indexing is used for search and
    retrieve functions in large and sophisticated databases or large collections of text. Nevertheless,
    indexes or the 'indexing overhead' for large full-text databases can take up considerable space in the
    CD.

Injection Molding

    This is a common industrial process to produce plastic products of all shapes. The CD-Digital Audio
    mastering and replication plants are costly and highly clean environments, because of the precision
    required to produce acceptable CDs. The injection molding machines fitted with appropriate
    stampers, stamp or press the molten polycarbonate. Thus, the replicate (also known as substrate) is
    allowed to cool before it is moved for metallizing and given a coat of protective lacquer. Most injection
    molding machines produce about 5 replicates per minute; some of the newer machines run at near
    double that rate.

Integrity
      Integrity is another conceptualization of reliability. It is often expressed as a number of erroneous
      bytes (characters) read per number of bytes read--after error detection and correction. The Yellow
      Book specifies a much more effective scheme than that in the Red Book. In fact, the industry's figures
      for CD-ROM integrity are 1 in 10 exp(13)--or about one erroneous byte in ten trillion! Assuming that
      two CD-ROMs involve about a gigabyte, we should expect an erroneous byte in about 5,000 CD-
      ROMs!

Interchange Levels

      The ISO 9660 defines three downward compatible levels of interchange--which define the length of
      filenames, and the ways they can be recorded in a CD-ROM. Level 1, which is more restrictive but
      compatible with MS-DOS, is obviously the most commonly implemented. The expectation is that the
      increasing demand for multi-platform applications will push the implementation of levels 2 and maybe
      even level 3 features.

Interface

      In computers, a user interface is that software component that the user sees, interacts with, and
      employs to control and navigate the application. In more sophisticated database environments,
      common interfaces refer to software programs that enable users and operators in different computer
      environments, when appropriately connected, operate a specific program on a main computer or
      network.

Interleaving

      In terms of CD-ROM encoding, where the track is a single spiral line, it means the appropriate
      interposition of portions of files, of different data types (text, video, audio, graphics, etc.), so that the
      application can use it for the most coordinated display or output (making it seem as displaying varied
      data types at the same time). The process is performed at the sector or logical block level (if the
      sector has been broken down to that level). Although the ISO 9660 provides specifications for
      interleaving, it seems that only CD-ROM-XA applications have implemented them with success.

ISA Bus

      The Industry Standard Architecture bus, introduced by IBM in the early l980s, is a motherboard with a
      16-bit data bus that was freely copied for the manufacturing of IBM-compatible PCs. Although never
      approved by a standards-setting organization, the ISA bus was common to most 286, 386, and 486
      Pcs. Its limitations became clear in face of the new faster CPUs (486, Pentium, etc.) that can operate
      on 32-bit data slices or chunks, and can address larger amounts of RAM. Today, only low-end PCs
      are sold with ISA bus motherboards.

ISO

      The International Standards Organization, composed of scores of international specialized
      committees, with main Secretariats worldwide, is the accepted source of standards for electronic and
      computerized data communications and information processing within the Open Systems
      Interconnection (OSI) framework.

ISO 9660

      Issued by the International Standards Organization, its formal title is ISO 9660: Information
      Processing--Volume and File Structure of CD-ROM for Information Exchange (1988). This multi-
      platform logical structure has been the key standard for the growth and worldwide acceptance of CD-
      ROM as a publishing and information distribution media and, since then, as the basic format structure
      for other implementations of CD-ROM in the computer arena.

Jewel Case
   This is the plastic shipping and storage case for CDs. Although the original practical design of the
   jewel case received no compliments, it is still used throughout the industry. There is, however, a
   veritable growth industry in light CD-ROM mailers, storage packets, and colorful mailers--especially
   for promotional mailings.

JPEG

   A versatile and commonly used color graphics compression specification adopted by the Joint
   Photographic Experts Group. Hardware and software JPEG implementations allow setting the desired
   compression, from 24-bit lossless (usually 2:1) to smaller bit size lossy compression rates (up to 60:1
   in some cases). This allows users to insure retention of detail and precision of the original. For
   everyday graphics work, recommended JPEG compression ratios range between 25 and 35:1.

Jukebox

   CD-ROM jukeboxes allow users to access collections of CD-ROMs. There are various types of CD-
   ROM jukeboxes, with different capacities (Pioneer has one with 500 CDs, and Disc apparently has
   one with 1478 CDs.). Some implement more than one drive, and other recent versions claim to
   support major LAN configurations. Some jukeboxes can be configured with multiple drives and even
   CD-R 'writers.' Some use 'optical jukebox' to refer to jukeboxes with WORM and Rewritable discs.

Kbps

   Kilobits per second (1000 bits/sec) is a measure used mainly in computer communications, for
   transmission rates and hardware bandwidths.

Kilobyte

   In computer usage, this basic number means 1024 bytes, which is 2 to the tenth power. It is used to
   account storage capacity, file lengths, and other byte-related amounts. Currently, larger multiples are
   already in everyday use, such as Megabyte, Gigabyte and so on.

Kodak Photo CD

   This product, was introduced by Kodak and Philips, in l992. The Photo CD is a hybrid disc that uses
   the CD-ROM XA Form 1 sector structure to store up to 100 35mm photographs in one disc, in one or
   more sessions. The photographs are scanned into digital files (18 MBytes--compressed to about 4.5
   MBytes, each), in five different resolutions. The Kodak Photo CD player displays on a TV monitor, but
   a multi-session CD-ROM XA drive, with appropriate software, can display on a PC monitor. When
   issued as a Bridge Disc, it can be played by Photo CD and CD-I drives connected to a TV set. Older
   CD-ROM XA players need an appropriate interface (or a software patch) to display multi-session
   contents.

Label

   CD-ROM, and other optical discs, are usually labelled on the 'back' side. Earlier, the label was
   generally screen-printed at the replication plant, in up to three colors, as part of the basic price. Today
   other printing options are also used, including some for the desktop as well as do-it-yourself kits
   designed for CD-Recordable one-offs. While labels have specific information about the product, they
   should also include the industry's 'DISC' logo that identifies the disc as an CD-Audio, CD-ROM, CD-I,
   etc.

LAN

   Local Area Network (LAN) and Wide Area Network (WAN) technologies have incorporated optical
   devices into most of their architectures. Some sophisticated servers now enable multi-user access to
   CD-ROM drives and CD-R recorders throughout the network.
Lands

   During recording of a glass master disc, a high power concentrated blue argon laser beam burns pits
   on the specially prepared recording surface. The 'lands' are the clear spaces between those pits.
   During reading, since the lands and pits reflect the read laser light differently, the transitions between
   them are detected and decoded to produce the 1s, and the lands provide the 0s, in run lengths.

Laser

   Light Amplification by Stimulated Emission of Radiation was demonstrated about half a century ago,
   with an original ruby laser. Today, lasers abound to suit diverse technologies and applications. Some
   magazines have reported tests of blue lasers of higher precision, which will make possible higher
   density optical discs.

LaserCard

   A small card that has a special backing (includes a recordable layer), and can be recorded and read
   by special drives (optical card readers). The Drexler process employs ablative write-once technology,
   and can store about 3MB of data.

LaserVision

   Introduced in l978, the LaserVision disc was one of the original implementations of optical technology.
   It was used to record video (analog), and became prominent in the interactive video training and
   educational market. With the popularization of PCs, LaserVision was used in the eighties in
   applications that combined PC software and interactive video.

Lead In--Lead Out

   These are lengths of track before the beginning and after the end of the coding. In single session
   applications, they serve as 'markers;' the lead-in includes the Table of Contents, and the lead-out can
   include code to stop the player--since there is no more application code in the track. CD-Audio tracks
   (songs) implement lead in and lead out to help song selection. In mixed-mode applications, each
   track with different type of data (text, video, audio) is required to include pre-gap and post-gap
   spaces.

Logical Structure

   In the computer industry, operating systems are designed to use a particular logical structure for data
   storage. For CD-ROM, however, the ISO 9660 specified the standard volume and file format to serve
   various computer platforms or operating systems. With appropriate modifications, this standard is
   making it possible for CD-ROM to involve text, graphics, audio and video for various types of CD-
   ROM implementations.

Lossy/Lossless Compression

   Certain compression algorithms can produce outstanding compression ratios, but often at the cost of
   imperfect decompression; that is, the decompressed data is not identical to what it was before
   compression. Imperfect decompression (even if only a few bits per millions of bits) is called lossy--
   because of the loss of bits affects data integrity. Lossless compression, on the other hand, employs
   algorithms that do not lose data in decompression, and although they may not produce great
   compression ratios, they provide integrity or reliability. When working with graphics and sound, some
   lossy compression is considered adequate, especially when storage space is a serious consideration.

Mass storage

   This is a relative concept. When PCs were introduced, 10 MB hard drives were considered adequate
   mass-storage devices--with little argument. For current PCs, magnetic disks of one gigabyte or two,
   CD-ROMs and optical discs are common mass storage options. Indeed, the pressure for larger
   storage devices will continue. It is likely, however, that mass storage in the future will involve chips, or
   cards, rather than magnetic or optical discs.

Mastering

   Mastering involves producing a glass master disc that is necessary for the mass reproduction
   process. Mastering takes place in a 'clean' environment, where the encoders use a high power blue
   argon laser beam to 'burn' pits on a large glass disc coated with a sensitive recording layer (usually
   photoresist). Once treated or 'developed' (chemically), the glass disc is referred to as the master or
   positive. Using electroforming technology, this glass master serves for the production of a metallic
   master (usually nickel), generally known as the 'father.' (It is also called a stamper, if it is used for
   reproduction of small runs.) For large mass reproduction jobs, the 'father' is used to produce
   intermediate 'mother' molds which are used to produced the necessary metal stampers ('sons' or
   production stampers) that are used in the injection molding machines. Mastering and reproduction are
   usually done at the same plant.

MCA Bus

   Micro-Channel Architecture Bus, introduced by IBM in 1987, is a 32-bit bus that can allow access to
   over 64 MBytes of system RAM. The versatile MCA bus, also allows post-installation configuration of
   adapter cards using a software program. At the outset, because very few CD-ROM manufacturers
   supported fully the MCA bus, users faced higher prices for CD-ROM drives with controller cards for
   the MCA bus. For various reasons, the PC industry has not followed IBM in the use of micro-channel
   technology.

Media

   In the computer arena, media usually refers to storage media- -which are varied and changing (glass
   or metal discs with magnetic coating, plastic discs with magnetic coating, CD- Recordable discs,
   paper cards with magnetic coating, etc.). In CD-ROM circles, media most often refers to archival and
   transfer media. Thus, at first, CD-ROM images were placed on magnetic 9- track 1/2 inch tapes for
   transfer to mastering plants. Then, 4 and 8mm Exabyte tape cartridges became widely used.
   Recently, CD- Recordable discs (one-offs) are becoming the preferred transfer media. All these
   transfer media are accepted by most mastering and replication plants.

Megabyte

   A Megabyte (MB) is 1024 KBytes, or 1,048,576 bytes.

Metallic coating

   After injection-molding and cooling, each disc undergoes metallizing--a process that gives the CD a
   metallic coat and its typical shiny surface. This coating reflects the laser light during the read process.
   For mass reproduced CDs, this coating is generally aluminum, but CD-Recordable, Write-Once and
   Rewritable discs use a gold-based coating for the same purposes.

MIDI

   Musical Instrument Digital Interface, provides a coding format for reproduction of sound in MIDI
   instruments. MIDI interface cards allow computers and other equipment use the MIDI coding. Most
   sound cards support the MIDI format. Because it does not involve sounds, but instructions and codes
   about the properties of the sound, the MIDI format is platform independent, and computer users can
   manipulate MIDI files to great advantage. Plenty of MIDI files are available in public bulletin boards
   and other sources.

Micron
   One millionth of a meter, a thousand of a millimeter. The CD-ROM track is generally 2.2 microns
   wide, and the pits are about 0.6 microns wide.

Microsecond

   One millionth of a second.

Mini-Disc

   An erasable optical disc, usually 8cm in diameter.

Mixed-Mode Disc

   Mixed-mode refers to a CD-ROM that includes CD-Digital Audio sound. Generally, the application
   (programs, data, indexes, etc.) are in Track 1, which is Mode 1. Audio begins in Track 2, and can be
   up to 98 CD-DA tracks. For Mixed-Mode discs, most CD- ROM players are equipped with CD-DA
   audio output plugs (except some earlier models). Similarly, the earlier CD-DA players did not have
   the feature that would ignore the data track of Mixed- Mode discs, which resulted in harsh sounds
   when that first track with data was 'played.'

M-O Technology

   Magneto-optical technology is the most used recording technology in the Rewritable (a.k.a. Erasable)
   line of optical products. The substrate is covered with a complex stack of thin films or layers--one of
   them the recording layer (of iron, cobalt and terbium), in which the pits are recorded. Two such discs
   are glued together to make the 5.25in, double-sided M-O disc--although double-sided 8cm (3.5in)
   discs are used in some devices. M-O discs can be rewritten millions of times, because the technology
   employs a magnetic field to realign (polarize) the molecular structure of the pit to its original unwritten
   state. This process exploits the Curie and Kerr effects, and does not move or effect physical changes
   in the coding layer, and therefore accounts for the functionality of the rewritable disc. The major
   drawback some see in M-O is that the process takes multiple passes to seek the area, erase, write,
   and verify-- which, according to detractors, make it a slow performer. Under the rather recent Orange
   Book, Part 1 (M-O), magneto-optical technology is employed on the 12cm CD, formatted following the
   ISO 9660 specifications. Unlike the M-O discs with proprietary formats in various sizes, the standard
   CD-MO product has given rise to new types of drives. The multi-function drives, for example, are able
   to read and write the CD-MO ('Rewritable CD') and read a standard ISO 9660 CD-ROM as well.
   There is expectancy for the growth of the CD-MO technology in the PC platform.

Mode 1

   Under the ISO 9660, a CD-ROM sector can be Mode 1 or Mode 2. Mode 1 allocates 2048 bytes for
   user data, plus a third layer of error detection and error correction codes. This is the Mode that
   provides the highest integrity for computer data.

Mode 2

   Under the ISO 9660, a Mode 2 CD-ROM sector allocates 2336 bytes for user data, and the additional
   codes for only the first two levels of error detection and error correction. It is therefore generally used
   for segments of music or graphics, and in CD-ROM-XA and CD-I implementations.

Modem

   A computer peripheral device that employs a digital to analog converter (DAC) to MOdulate and
   DEModulate the data stream from binary to analog and viceversa. Therefore, modems allow
   transmission of computer data through telephone lines.

Modulation
   Modulation is generally used to refer to analog to digital conversion. There are however, various other
   modulation schemes. For example, CD Audio players use a digital to Analog converter to produce the
   stereo analog music signals. To produce the appropriate mix of sounds in the signal, the system uses
   Pulse Code Modulation (PCM)--although Adaptive Digital Pulse Code Modulation (ADPCM), and
   others, have been implemented in other audio applications.

MPEG

   A CODEC adopted by ISO's Motion Pictures Expert Group for compression and playback of full-
   motion video and audio streams-- often referred to as 'MPEG video.' MPEG-1 is now an open
   standard (ISO/IEC 11172, 1991)--which establishes the structure for a standard MPEG file, and
   specifies a transfer rate of 1.5Mb/sec, with a resolution of 352x240 at 30 fps. MPEG-2 accepts
   transfer rates up to 15MB/sec, with a high resolution of 720x480 at 30 fps, and it also requires a 2MB
   buffer. Although MPEG makes heavy demands on the CPU, most of the demands of multimedia in
   CD-ROM today are met by various MPEG add-on boards. Incidentally, CD-I uses MPEG-1, and
   Video CD was promoted as the first MPEG-1 optical disc for multiple platforms. For the PC
   multimedia platform, the API for program interface with MPEG decoders, however, is not standard.
   The more used is the OM1 API developed by MCI, adopted by Microsoft, and by many others as well.
   MPEG add-on boards use special chip sets (such as those from C-Cube Microsystems) for
   compression and decompression--but there are various software-only MPEG decoding programs.
   High-end hardware solutions claim compression ratios up to 50 to 1--which is about what is needed to
   display at 30 fps. But, since MPEG is lossy, such high rates often signify lower quality playback at 30
   fps. At the decoder level, there are three main types of solutions for the PC platform: overlay,
   combination boards, and software-only. Most of them (except the software-only) claim to provide 30
   fps with a Pentium PC. MPEG-2 (ISO 13818-1, l994) offers higher quality and speeds than MPEG-1.
   In certain circles, it is promoted as a step to a software MPEG solution, because future PCs are
   expected to have CPUs capable of processing the coded stream from 500kb/sec to about 2.0
   MB/sec. There are many MPEG-2 hardware solutions (add- on boards), but the 'software MPEG'
   products are also making their mark. British OmniMedia's Software MPEG, for example, offers a rate
   of 20 frames/sec with a Pentium 75 PC. Industry observers comment on the wide use of MPEG-1
   outside of the US, especially in Asia, while the US side, in their view, seems to be waiting for MPEG-
   2. In the meantime, many lowcost proprietary solutions have entered the marketplace. The Open
   MPEG Council, a recently formed industry group, hopes to standardize MPEG in all sectors of the
   multimedia industry so that all MPEG-based products will work without problems in the DOS-
   Windows platform first, and in other platforms later.

MSCDEX.EXE

   Known as the Microsoft CD-ROM Extensions, the MSCDEX.EXE program became necessary when
   CD-ROM drives were introduced to the PC platform--and to stop the growth of proprietary extensions
   and CD-ROM file managers. With the appropriate CD-ROM device driver loaded, MSCDEX.EXE
   enables the PC to configure the drive (by giving it a drive lettername), and to access the contents of
   ISO 9660 CD-ROMs. Other platforms have equivalents to MSCDEX. The Apple/Mac platform,
   although it can use HFS and Apple CD-ROM extensions, it can also use its Foreign File Access to
   deal with ISO 9660 CD-ROMs. MSCDEX.EXE is included in MS-DOS and Windows.

Multimedia

   This is the new, exciting, and growing arena of applications that use CD-ROM. Multimedia
   applications include text, sound, and motion video in what are mostly new categories of informational,
   educational, and entertainment products--and which have also helped define the new arena of
   'infotainment.' Multimedia uses CD-ROM as its main file storage device. But, since video files can be
   very large, multimedia has led to the growth of specialized software, efficient hardware, and
   compression solutions. Some aspects of multimedia are subject to specifications issued by the
   Multimedia PC Marketing Council, currently listed in the MPC Level 2 System Requirements.
   Multimedia implementations in CD-I, however, use DYUV for graphics, MPEG for video, and ADPCM
   for audio--and display in a rather low resolution (340x240). IBM also proposed specifications for
   multimedia, known as Ultimedia, but they have not taken hold. In the Mac arena, users have been
   less hampered by hardware problems because the Mac comes configured to deal with CD-ROM and
   multimedia demands--and some Mac users think Hypercard is also a satisfactory multimedia
   authoring tool.

Multi-session

   In optical technology, this refers to a disc that has been encoded in more than one session.
   Therefore, the disc has more than one 'volume'--reason why it is also known as multi-volume. During
   recording, the volumes are provided their own Lead-In and Lead-Out areas. The multi-session disc,
   however, has a overall Table of Contents (TOC) that is written at 'closing'--after the last session is
   recorded. In some implementations, individual volumes (sessions) write their tables of contents in
   their Lead- in area, and other implementations update the overall TOC. A multisession drive has to be
   able to read the contents of all the volumes in the disc (regular drives can only read the first TOC).
   Kodak Photo CD, and CD-ROM-XA and CD-I implement multi-session features, but only some recent
   XA drives are truly multi-session capable. Multi-session specifications were proposed by the Frankfurt
   Group, and were initially circulated by the European Computer Manufacturers' Association as
   Working Paper TC 15.

Non-ISO 9660 CDs

   This category includes CD-ROM products in other proprietary formats, and as test products for other
   platforms. There are, for example, CDs formatted as Apple HFS products. Since mastering and
   replication can be done for any format, and new CD-Recordable hardware is proliferating, non-ISO
   applications can be produced in all computer platforms--with the appropriate formatting software.

NTSC

   The National Television Standards Committee supports the NTSC signal and display technology used
   in the TV industries of North America, Japan, and a few other countries. It specifies 525 lines/screen,
   and 29-30 frames/sec.

OCR

   In computing circles, Optical Character Recognition involves scanning hardware and software to
   produce computer usable text files from printed pages--as opposed to producing a graphic image of
   the page. Essentially, the OCR software recognizes the dot patterns and produces characters. OCR
   technology has improved remarkably, and with more powerful CPUs, it will increase its reliability and
   other factors. For documents with complex layout, uncommon or unclear fonts, and in old or dark
   color paper, keystroking is often the best option.

Operating Systems

   Generally, an operating system refers to the set of internal (kernel) and external commands and
   subroutines that allow the computer to manage its components. Most operating systems require
   (cards or software) interfaces to deal with peripheral devices (MS-DOS, Mac, OS/2, Unix, etc). CD-
   ROM drives, and most other optical devices, are usually packaged with an appropriate interface card
   and connecting cable. SCSI CD-ROM drives either come ready to connect to a 'standard' SCSI-2
   card, or come with a SCSI card of their own--for the appropriate operating system. Therefore, the
   same drive can be used in various platforms.

Optical discs

   Technically, optical discs are those that are 'written' (encoded) and read using a laser optical device.
   Some of them are mastered and mass-reproduced (such as CD-Audio and CD-ROM), and others are
   produced individually, by an optical drive connected to the computer (Write-Once, Rewritable, and
   CD-Recordable). The optical industry is clearly divided; with the mastered and mass-reproduced
   12cm CD-ROM implementations in one camp, and all the other discs in the 'optical' camp. CD- Audio,
   obviously, is an industry of its own.

Optical Recording Technologies

   Although often referred to as encoding, optical recording technologies are varied and quite
   sophisticated--the main ones are summarized below. For CD-Audio and CD-ROM, which are mass-
   replicated products, a glass disk, coated with photoresist, undergoes recording, development, and a
   special process to produce the metallized glass master--which is then used to produce the stampers
   for the reproduction equipment. On the desktop, W-O and Rewritable drives record the optical discs
   in real time, one at a time. CD- Recordable drives encode either in Track-at-Once (TAO), or Disc- at-
   Once (DAO) mode in the same CD-Recordable media. All those discs (media) are produced with a
   recording layer prepared for the specific recording technology to be applied. W-O uses Ablative,
   Phase Transition, Bubble Formation, Alloy Formation, and Texture Change recording technologies.
   Ablative technology, which is the most common, uses a recording layer with tellurium alloy (low
   melting point) that allows formation of holes when the high power laser beam is applied--thus forming
   holes or 'pits.' In similar fashion, the other technologies produce some sort of 'pit' by a phase, color, or
   texture change. Rewritable uses Magneto-Optical (M-O), Dye Polymer, and Phase Change recording
   technologies. M-O is the most common, and it uses a magnetic film (of rare earths) for the recording
   layer, an appropriate magnetic field, and a high power laser beam to record or 'rewrite'--applying the
   Curie and Kerr principles about changes in structure when heat is applied, and the realignment of
   particles (polarization) when a magnetic field is present. Dye polymer and phase change also use
   special recording films or layers, on which the write laser produces the pits. The pits in these
   technologies are, however, erasable--they can be reverted to their original state--therefore the disc
   can be rewritten. Some important vendors are adopting phase change technology (which can erase
   and write in one pass), and are making it a serious competitor of M-O technology. All these recording
   technologies produce pits that reflect light with less intensity than the lands about them. The changes
   in reflectivity, as the laser passes over them, are detected and decoded to reproduce the original
   data.

Optical Technology

   Technically, optical technology refers to all processes that involve light, lenses and other devices
   dealing with transmission of light (cameras, the eye, microscopes, etc.). In computing circles,
   however, optical technology refers to that used in CD- ROM, Write-Once and Erasable drives. All
   these devices use high power lasers to encode the data on the disc, and low power lasers and
   photodiodes to read the codes. The 'heads' employed to 'write' and 'read' the code involve sets of
   precise lenses and servo-mechanisms that guide the laser beam as well as focus it with great
   precision. Obviously, any type of coding that can be converted to digital code can be transferred to an
   optical disc. CD-Audio and CD-ROM are mass reproduced optical products, while Write-Once,
   Erasable and CD-Recordable discs are produced individually. Current optical devices need only
   appropriate interface cards to work with computers.

Orange Book

   The Recordable Compact Disc Standard was published by Philips, in l990, reportedly in a binder with
   Orange Covers. The Orange Book defines two new 12cm CD products: the Magneto-Optical and the
   Write-Once. Part 1, Magneto-Optical (CD-MO), defines tracks that can be erased and rewritten--
   reason why this format is more appropriately known as Rewritable. M-O drives implement magneto-
   optical recording technology, on 12cm CDs that are rated to allow millions of rewrites. These drives
   are however slower than other optical drives, because they use two heads--one to erase and the
   other to write, in a double-pass process. Some CD-MO products include a small premastered Read-
   Only area that usually contains system and other information--but which can also be read by a regular
   CD-ROM drive. The remainder space is the Recordable User Area, and the user can reuse this area
   at will. Despite the original optimism for rewritable M-O drives, they are still not yet priced low enough
   to compete with magnetic drives. Part 2, Write-Once (CD-WO), defines tracks that can be written to,
   but not erased and rewritten--in the tradition of WORM (write-once read-many) discs. A Write-Once
   drive records appropriate 12cm CDs--which involve special recording layers, pregrooved tracks and,
   generally, a gold reflective layer. The initial tracks include a Program Calibration Area, are followed by
   a Lead-In area (where the Table of Contents will be written), and by the Program Area--for the user
   data. The recording session is finished with the Lead Out. A CD-WO 'Hybrid' disc involves an area
   where Read-Only files can be placed, and the rest of the disc is the W-O area. CD-WO drives remain
   relatively high priced, and although the media has reduced in price, CD-WO is still used mainly in
   enterprise archival and imaging.

OS-9

   This is an operating system, implemented in microcomputers specifically for CD-I.

Overhead

   Full-text search and retrieve applications that involve large collections of text rely mainly on indexing
   to produce speedy results. Some database applications with superior functionality rely heavily on
   indexing. Indexes, however, can be very large, averaging between 30 and 50 percent of the textbase,
   and in some cases much more. Those indexes are often thought of as overhead, and provisions must
   be made for it in the arithmetic of disc capacity and design.

Packaging

   Once the CD-ROM is produced, it has to be prepared for distribution. Generally, besides the labelling
   of the CD-ROM itself, most replication plants offer printing services for jewel case inserts, manuals,
   and other information to fit in or accompany the jewel case. Once all the items are ready and
   assembled as desired, they are either shrinkwrapped or stuffed into appropriate envelopes or mailers.
   Some replication plants even offer mailing services. Obviously, the artwork for the disc label and
   insert, the masters for printing, mailing lists, and all other necessary items must be provided in
   advance, in the format specified by the plant. Promoters and sellers try to make sure authors
   recognize the role of packaging for the success of the product, and they have been proved right too
   often to ignore their recommendations.

PAL

   Phase Alternation Line, a television standard, is used by European, Asian and some Latin American
   Countries. It specifies 768 pixels/line, 576 lines/screen and 25 frames/sec.

PCI Local Bus

   The Peripheral Communications Interconnect Local Bus, introduced by Intel and associated
   manufacturers (1993), is a sophisticated local bus--considered superior to the VESA local bus. It is a
   32-bit bus, with a maximum transfer rate of 132 MBytes/sec., that can handle up to ten devices (three
   of which can be add-on boards). It is currently used mainly by the Pentium based PC platform, and it
   is expected that PCI Local Bus interfaces for optical devices will be part of the design in future
   versions.

PCM

   Pulse Code Modulation is implemented to structure the analog signal that is produced by the digital-
   analog converter of the CD-Audio player. PCM, therefore, makes it possible to hear the various
   instruments, their different ranges and depth of sound, etc., and is considered the better scheme. It
   was the basis for ADPCM, which was implemented in CD-ROM-XA and CDI.

PCMCIA

   The Personal Computer Memory Card International Association addressed the need for small and
   portable devices for the growing portable, notebook and other hand-held computer production lines.
   The PCMCIA developed a new interface (with connectors in three sizes), which essentially senses
   the device connected, identifies it, and makes it available to the user. Since the devices implement
   PCMCIA electronics, they can be attached to or removed from the bus at any time.

Phase-Change Technology

   This rewritable technology employs a recording layer (one of the special films on the substrate) that
   shifts phase, from amorphous to crystalline, when the 'write' laser beam is used. To erase, a laser
   beam of higher power heats up the area and, essentially, melts it--which then cools to the amorphous
   state and is therefore ready to be written again. Since phase-change made possible 'single pass'
   erasing and rewriting, vendors claim that their phase-change drives provide faster operation than M-O
   drives, and that its slight advantage in storage capacity will play a bigger role when discs of over one
   Gigabyte become common. Some industry magazines claim that it has already reached about 30
   percent of the rewritable market, challenging the popular M-O drives. In 1995, Panasonic introduced
   a Phase-Change multifunction drive, at a very competitive price, reflecting the trends in the
   Rewritable industry.

Physical Format

   Media-specific structure that dictates how the data is laid out in the disc, data modes, error detection
   and correction, physical sector addressing, and other characteristics necessary to manage the type of
   data intended for the media. The volume and file structure for the contents are dealt with by a logical
   format.

Pits

   During optical encoding, bursts of a high power (usually a blue argon) laser beam 'burn' microscopic
   'pits' on the recording layer. The untouched spaces between such pits are called 'lands.' During the
   read process, the laser light focuses on the spinning track, and since the pits reflect light less
   intensely, the read head detects the changes in reflectivity, and those changes are processed to
   produce a binary data stream.

Pixel

   A Picture Element, used mainly in graphics and video circles, is the smallest unit of display that can
   be given color and intensity values or codes.

Pre-gap/Post-gap

   These are empty lengths of track (two seconds, or equivalent, of nothing but 0s), which are placed
   before and after the data track.

Premastering

   Too often, this term is used quite broadly. Data preparation, indexing, testing (also called simulation),
   and creating the 'image' are done before premastering. Premastering involves taking the 'image' of
   the application and producing the premastered file--one large ISO 9660 volume file (a chain of CD-
   ROM sectors, with sector addresses, header, synchronization, error correction and detection, mode,
   and other required bytes). The premastered file is further processed for the production of the glass
   master. The hardware and software used for premastering are usually known as 'ISO formatters,' and
   they vary in capabilities and features. When using a CD-Recordable drive premastering takes place
   as the program records the 'one- off.'

Pressed Discs

   Some circles in the industry use these terms to distinguish the mass reproduced discs from the
   rewritable, write-once, and CD-Recordable discs that are produced one by one, on the desktop.

Program Area
   This term, introduced in CD-Audio production, refers to the area of the disc where the user files are
   stored. The program area is between the Lead-in and the Lead-out. The user data, indexes, and
   other files that go in the program area are placed in the most appropriate order--to reduce seek and
   access times.

Protective Coating

   Optical discs are given a clear plastic or lacquer coat that protects the metallic layer. Even with this
   coating, small scratches, pressure, dirt and other markings can make the disc unreadable. The
   coating also prevents air from reaching and oxidizing the metallized layer--which would render the
   disc unreadable.

QuickTime

   Initially an Apple only product, now found in Windows and being ported to other platforms, QuickTime
   is a multifeatured program that plays sounds, animation, and video files in a time- based programmed
   mode--although the display is only about one- third of the screen (.MOV files). QuickTime movie
   authoring involves file compression and on-the-fly decompression. While it supports Intel's Indeo
   decompression, the adoption of MPEG compression/decompression should make it more popular.
   Some multimedia products bundle QuickTime, and is found in many bulletin boards and the Internet.

RAID

   Redundant Array of Inexpensive Disks is a large storage scheme used increasingly more in large
   imaging systems, and industrial multimedia developing systems. The newer RAID systems offer high
   reliability and claim (fiber channel) transfer rates near 100 MBytes per second, and expect to transfer
   above that figure soon. RAID's versatility, software and hardware dependent, includes levels of
   security, recovery after network or drive failure, 'hot swapping,' compression and other sophisticated
   options.

RAM

   Random Access Memory, also known as 'system memory,' is that amount of physical memory that is
   addressable by and directly accessible to the CPU--chips on the motherboard, or on an add-on board
   on the bus.

Raw Capacity

   Optical discs include substantial overhead in the encoding, to work effectively, and to provide the
   integrity required for computer data. For any CD-ROM, in percentages, the overhead includes: the
   bytes used by the required eight-to-fourteen modulation (34%), the merging bits (17%), the error
   detection and correction codes (11%), and synchronization and subcodes (5%). This leaves about
   33% net space for user data. Efforts to improve the capacity of optical products are also focusing on
   these overhead areas.

Reed-Solomon Codes

   These are error detection and error correction codes, based on mathematical algorithms and binary
   structural logic. The Red Book implemented the basic two levels of error detection and correction
   using Cross Interleaved Reed Solomon Codes (CIRC). The Yellow Book specified a third level of
   'layered' error detection and error correction codes, to attain the level of integrity that computer data
   require. Another scheme of Reed- Solomon error detection and correction will be used in DVD.

Recording Layer

   This is the sensitive layer, deposited over the substrate, which reacts in a specific way when a high
   power laser beam is focused on it. Each recording technology uses an appropriate recording layer--
   which can be Photoresist, a special dye, special alloy, or a sandwich of sensitive films. For mass-
    reproduced CDs, the initial glass disc that is encoded (master) usually has a Photoresist recording
    layer.

Red Book

    Philips and Sony, developers of the CD technology, and of the 12cm CD, published their
    specifications for CD-Audio in l980- -reportedly in a binder with red covers. The Red Book addressed
    the physical specifications for the CD; the tracks, the sector and block layout, coding and sampling of
    digital audio files, and other specifications. The Red Book was key for the high quality sound of CD-
    Audio, which became a standard and a major world industry of its own. The International
    Electrotechnical Commission published the Red Book as their Doc IEC 908.

Reflectivity

    A measurable property of a surface. In optical technology, baseline reflectivity refers to the reflectivity
    of the 'lands'-- the clear spaces between the pits in the data track. The pits have lower than baseline
    reflectivity. In optical discs, the changes in reflectivity are detected and decoded, and then converted
    to magnetic coding.

Replication

    In optical technology, replication refers to mass replication, as in CD-Audio and CD-ROM. Mass
    replication made CD-Audio a competitive product. In fact, since the same CD-Audio mass replication
    plants produce CD-ROMs, they made possible low CD-ROM production costs--which were certainly
    crucial during the first years of the CD-ROM industry.

Rewritable Optical Discs

    Rewritable optical technology aims to produce drives that will replace magnetic storage devices in
    computers. Vendors claim that their rewritable optical disks can be erased and rewritten over a million
    times. There are three main types of recording technologies for rewritable optical discs. Magneto-
    Optical (M-O) technology is predominant. Phase Change technology follows far behind, but its
    adoption by new manufacturers keeps it in contention. The third is Dye Polymer technology, adopted
    by some manufacturers. Until recently, rewritable discs were mainly 3.5 and 5.25 inches in diameter,
    double sided, and of various capacities and proprietary formats. Currently, the Orange Book 12cm
    (4.72in) CD-MO appears to be growing. Recently, Panasonic released a new Phase-Change Drive
    that is supposed to read all rewritable (M-O, Phase-change, and Dye Polymer) discs, PhaseWriter
    Dual drives claim to read CD- Audio, CD-ROM and Rewritable discs, and Pinnacle Micro's Apex
    Rewritable 4.6 GB drive claims to read CD-ROMs at 16X speed, etc.

RIFF

    Resource Interchange File Format is used to store multimedia files, because it also allows their use in
    various platforms.

Rockridge Group

    This is an industry group that developed extensions to the ISO 9660 to produce ISO-compliant
    applications that could be played by multiple operating systems, emphasizing Unix-based or POSIX-
    compliant systems. Some saw the need for those extensions, especially since implementation of ISO
    9660 interchange levels was more problematic than first perceived. The proposed extensions,
    System Use Shared Protocol (SUSP), and the Rockridge Interchange Protocol (RRIP), allow for
    support of multi-platform formats, tables of contents with deeper levels of hierarchy, and the use of
    filenames larger than those allowed by MS-DOS. Essentially, those extensions make the ISO-
    compliant contents of the disc appear like a Unix File System to Unix machines configured to support
    Rockridge Extensions. Incidentally, in a different approach, there are applications for the Unix
    platform that include translation tables to show the contents of the CD- ROM with Unix-like file and
   directory names--but that is not what the Rockridge Group proposal specifies. It was expected that
   the Rock Ridge specifications be approved by the end of 1995.

ROM

   Read Only Memory. The term originally applied to read-only memory chips used in computers. With
   the growth of optical storage, the term read-only memory now applies to compact disc products (CD-
   ROM, CD-I, CD-ROM XA, CD-Recordable, etc.) WORM, now referred to as Write-Once, after the
   contents have been recorded, is also read-only.

Run-Length

   In CD-ROM, run-length specifies the number of contiguous 0s in the optical byte--between the 1s.
   This usage is related but not the same as run-length encoding (RLE), which is a compression
   algorithm used widely to compress graphics files.

Sampling

   Sampling is part of analog to digital conversion. Essentially, the analog signal is sampled at an
   specific rate and quantized--which means a numerical value is matched to each sample, and that
   value is converted to binary code. Although the frequency of sampling is important for continuity, the
   size of the sample (in bits) is important for depth of quality. CD-Audio involves sampling rate of 44.1
   KHz, and sample size of 16 bits.

Scanning

   Scanning involves hardware and software. Essentially, scanners apply a light (laser, and recently
   LED) to the source page, so that a set of sensors (charge-coupled devices) can detect the presence
   of black areas (or colors) and produce codes for each pixel, and those codes are processed into
   raster scan files. High end scanners, using appropriate chips and hardware, produce high resolution
   graphic files. Desktop scanners popularized the 300 bpi resolution, while fax specifications use 170
   bpi resolution. With appropriate software, some scanners can produce scan files in vector graphics
   formats. Most scanners, with appropriate software, can also scan documents for optical character
   recognition (OCR). The same principles guide the specialized scanners such as the hand-held
   scanners, bar code readers, slide and microfiche scanners, card scanners, pattern recognition
   scanners, and others.

SCSI

   The Small Computer System Interface was introduced as the 'intelligent interface for intelligent
   devices.' A SCSI card can operate in 8 and 16-bit buses, and serve up to seven (or even more)
   devices connected in a 'daisy chain'. The interface issues commands to the chain, where each device
   recognizes the commands addressed to it. SCSI hard disks store data in sequential blocks, and
   transfer (in parallel) at rates between 3.3 and up to 40 MBytes/sec (the newer implementations offer
   faster rates). Nevertheless, despite its many flavors, the fact that SCSI is an ANSI standard has made
   for solid commitments to it among some manufacturers. Currently, SCSI-2 (Fast, Wide, Fast and
   Wide) are in use. Ultra SCSI can support up to 15 devices, and is backward compatible. The SCSI-3
   specification, not yet published, is said to involve asynchronous (serial) mode implementations for
   fiber channels, HPSB and other new bus designs in the market.

Search and Retrieve

   Software operating on large amounts of data (full-text, databases, spreadsheets, multi-media, etc.)
   provide search and retrieve functions to help find the appropriate information efficiently. Most CD-
   ROM full-text applications use the now popular Boolean search and retrieve.

Sector
   Unlike the sectors and blocks used in regular magnetic storage devices, the sectors in CD-ROM are
   prescribed by the Yellow Book, in the physical format of the data track. The logical sector, on the
   other hand, is defined by the ISO 9660, and is the smallest addressable unit. In technical circles the
   difference between physical and logical sectors is clear. But, in general parlance it is not so clear
   because, under the ISO 9660, the physical sector (data user area of 2048 bytes) can be subdivided
   into Logical Blocks of 512, 1024 or 2048 bytes. And, since MSCDEX supports only logical blocks of
   2048 bytes, each Mode 1 sector's user data area is one logical block. This usage has caused many to
   consider physical and logical blocks as one and the same.

Servo Mechanisms

   These precise electro-mechanical devices with sophisticated components are employed for precise
   shifting of the read (and write) heads to specific tracks on the disc, to detect variations in the tracking
   of the pits and correcting any off-centering, to position the heads to the appropriate focal length for
   the laser as the disc rotates, and so on. The sophistication and precision of these devices can be
   appreciated better when one realizes that the tracks are 1.6 microns wide and that, in the older 1X
   drives, the laser is 'reading' pits and lands at a rate of about 75 blocks (150 KB) per second!

SIGCAT

   The Special Interest Group for CD-ROM Applications and Technology, based in Reston, VA, is now a
   non-profit Foundation dedicated to the promotion of CD-ROM technology in government and industry.
   SIGCAT is open to all; it has gained broad government and corporate support (government policies
   and CD-ROM implementation, hardware, software and application developers and vendors), and has
   a subscription list of over 9000. DISCourse, its newsletter, is mailed to all paid subscribed members.
   The BLER (Bimonthly Listing of Events and Resources) is mailed to all who sign up for it. SIGCAT
   has a Training Center that offers a varied program of courses and workshops, and its CIRC (CD-
   ROM Information Resources Center) serves vendors, software developers and mostly government
   users. The yearly SIGCAT National Conference is becoming a major event in the CD-ROM arena.

Simulation

   Developers 'simulate' the application, when it is considered finished, but still in the computer. It
   involves testing the software, interface and data, as if it were in the CD-ROM. There are simulation
   software packages that can measure retrieval speeds, output features, screen building, and other
   features. If some features are found lacking, they can be improved and retested until they are
   satisfactory. Simulations are cost- effective, because they are performed before the expensive
   mastering and replication. In some CD-Recordable drives, Simulation is a feature that transfers the
   data but does not encode the disc--thus simulating the process. It shows that all is fine, or that the
   recording is creating errors or underruns--and saves ruining a clean disc.

SMPTE

   This is a timing code implemented by the Society of Motion Picture and Television Engineers. It
   employs hours, minutes, seconds, and frames to address the individual frames in a videotape--a
   framework not too dissimilar from that of CD-ROM. To use (NTSC) television signals, which flows at a
   rate of about 30 frames per second, appropriate SMPTE timing marks must be included for their use
   in CD applications.

Stamper

   A metallic mold (usually nickel) produced by electroforming, during the mastering process. For small
   runs, the 'father' (the first electroformed master) is used in the injection-molding machine. For large
   runs, the 'father' is used to produce intermediate molds and the final stampers that are placed in the
   injection-molding machines.
Stopwords

   In search and retrieve applications, stopwords are those words that the application designer wants
   the search and retrieve software to ignore altogether. A generic stopword list includes about 100
   common articles, adverbs, adjectives and other modifiers that are of no use in the logic of a full-text
   search. Also, eliminating these common words reduces clutter in the index tables--which also helps
   the search process.

Substrate

   This is the core of the CD. It starts as molten, clear polycarbonate, for the injection molding machines.
   After pressing and cooling, the core disc or substrate is metallized, given a lacquer protective coating,
   and labelled. CD-Recordable media has the same substrate, but different recording layers on it. In W-
   O and Rewritable media, the substrate is often glass.

Synchronization

   The Synch bytes help the synchronization of the read head onto the coding in a block (to engage it to
   begin reading at the right place). There are 12 synch bytes in a CD-ROM block.

TAR

   Tape Archival and Retrieval format, used extensively during the reign of the mainframes, served to
   place files on tapes that could be retrieved by computers with a different operating system. Some
   government information, for example, was sold to the public in TAR format.

Termination Resistors

   These small plastic contraptions are placed at both ends of the chains of devices in a SCSI
   configuration. Their role is, essentially, to signal that there are no other devices beyond that point,
   and prevent excess signal noise on the SCSI bus.

TOC

   Table of Contents generally implies a list of the files and addresses of a CD-ROM application. In
   current multi-session applications, each session involves its own table of contents-- and the
   application scans the disc and begins to read the last table of contents first. In magnetic drives, since
   file sizes can change and be broken into parts, the FAT (file allocation table) is the system's TOC,
   because it is an updatable table of file locations (addresses and distribution) for the entire drive
   (logical partition).

Track

   Optical technology uses Constant Linear Velocity rotation, which involves a spiral track of coding that
   begins near the center of the disc. This track has a pitch of about 1.6 microns and, in a 63-minute
   disc, it is about 3 miles long. At another level, in mixed-mode or multimedia applications, we say that
   data types are in 'separate' tracks--but they are in the same physical track, using appropriate
   interleaving.

Track Access

   The common method to access 'songs' by track number in CD- Digital Audio. Under the Red Book, a
   disc can have 99 tracks, and under the Yellow Book, it can have up to 98 tracks of CD-DA tracks (the
   first track must be Mode 1 data track). Therefore, mixed mode discs implement other access
   methods.

Transfer Media
   Initially, mastering plants accepted the image of CD-Audio or CD-ROM applications in a few specific
   magnetic transfer media: 9- track, 1/2in. tapes were the most popular. In time, large capacity 8mm.
   Exabyte tapes, 4mm Digital Audio Tapes, and similar media became acceptable transfer media.
   Currently, mastering plants also accept CD-Recordable 'one-offs'.

Transfer Rate

   The first CD-ROM drives were designed to read 75 blocks of data per second, which means that 150
   KBytes of user data per second are transferred to the computer's CPU. This basic transfer rate is now
   thought of as 1X, because new drives claim to transfer at multiples of that rate--i.e. 2X, 6X, etc. In
   fact, although the current requirement by MPC Level 2 is a double-spin drive (2X), some multimedia
   applications recommend quad-speed (4X) drives. Current literature already mentions 12X drives.

UDF

   The Universal Disc Format was promoted by the Optical Storage Technology Association (OSTA), as
   a single file system for interchange of information in the computer arena. It was announced that
   OSTA will also develop a UDF-based file format for CD-ROM, write-once and rewritable applications.
   It is expected that this universal file format will help eliminate the broad incompatibility among write-
   once and rewritable applications, and with the CD-ROM arena.

UNIX

   This relatively old and powerful operating system, matured and spawned various versions in mostly
   academic, industry, and government research institutions. Recently, because of the Internet, the
   power available on desktop hardware, the growth of worldwide computer communications, and the
   efforts to standardize its code, UNIX is becoming another option on the PC platform.

User Data

   In CDs, the sectors include an specific space allocated for data used by the application (user).

VESA

   The industry group, Video Electronic Standards Association, joined to produce what they termed a
   non-proprietary response to IBM's Microchannel architecture. They did so by producing the VESA
   Local Bus architecture--known as the VL Bus. It is a 32-bit bus, with a maximum bandwidth of 132
   MBytes per second. It was designed to aid high speed video devices. The VL Bus Interface
   (additional circuitry and chips) extends the CPU bus, and thus can interact directly with the CPU and
   memory. However, In the 486 platform, this 32-bit interface was usually limited to only three VL Bus
   peripherals--and only two of them could be add-on boards. The power in the Pentium architecture,
   and the PCI bus, have reduced the need for the VESA LB.

Video CD

   The Video CD specifications ('White Book') were proposed by JVC and Philips (Aug93), and
   supported by other major players in the industry; but it has not been implemented as broadly as first
   expected. The CD is used to store 72-74 minutes of full motion video and digital audio, using an
   MPEG-1 decompression board, in a CD-ROM XA 'bridge disc.' (It was, essentially, derived from the
   'Karaoke video' concept.) Because CD-I players can play Video CD discs, it was considered another
   version of CD-I. Recently, Panasonic introduced a Video CD player (in various models), and also
   announced its promotion of Video CD titles for diverse markets. Similarly, Philips teamed up with IBM,
   Apple, Austin and others, to promote its line of Video CD players and Video CD titles.

Volume

   A volume is defined as a complete CD-ROM. Often, 'ISO volume' refers to a CD-ROM produced
   according to the ISO 9660. If the data, or large files, need to use more than one disc, then the entire
   product is known as a Volume Set. We must point out, however, that under the ISO 9660, Volume
   Sets can not be produced under Implementation Level 1. Moreover, multi-volume disc sets are not
   supported by MSCDEX.

Volume Descriptor

   The Primary Volume Descriptor is an area of 2 Kbytes, at the beginning of the track, that includes
   data and identifiers about the volume, the publisher, data origination, copyright, dates, etc.

W-O Technology

   Write-Once Technology, started with WORM (Write Once, Read Many) computer applications--which
   involved generally proprietary formats and hardware options. Philips developed the specifications for
   the implementation of Write-Once technology in the 12cm CD, in the Orange Book, Part 2. Essentially
   a W-O drive, with appropriate software, 'writes' the code onto the W-O disc, in one or more sessions,
   until the disc is filled. From then on, the disc is read-only--reason for the 'write-once' name. Currently,
   Ablative, Phase Transition, Bubble Formation, Alloy Formation, and Texture Change technologies are
   used for recording W-O discs--ablative technology being the most used. All these technologies
   involve a specially designed recording layer, which undergoes a specific physical change at the spot
   where the high power laser beam is focused--forming a 'pit'. As with all optical technologies, those
   pits cause changes in reflectivity, and those changes are decoded to produce the 1s and 0s of the
   code stream. Orange Book, W-O applications (12cm CDs), are found in enterprise document archival,
   audit trails, scientific record archival, imaging and imaging archival, and others. Currently, the growth
   of multifunction drives (M-O and CD-ROM), and of CD- Recordable, seems to have slowed the
   growth of W-O, but it is still too early to discount Orange Book, W-O technology.

White Book

   The White Book, produced by JVC and Phillips (l993), used the sector structure of CD-ROM-XA to
   produce a Video-CD ("bridge disc,' or a hybrid CD) that could be played in CD-ROM-XA drives, and
   CD-I players as well. Video-CD (which was derived from the Karaoke CD concept) uses full-motion
   MPEG. Another implementation of the White Book is the Kodak Photo-CD.

WORM

   Stands for Write Once, Read Many, the usage for optical technology that was applied since the late
   70s, in media of various sizes (5.25in, 12in, and even 14in). Most WORM media was double-sided,
   with capacities from 140MBytes to over 3 GB per side, depending on formats and encoding. The
   growth of WORM technology was hampered by the various proprietary hardware and software
   solutions, as well as by their price. Nevertheless it became predominant in archival (imaging)
   applications, especially for large enterprises and government agencies. Recently, Orange Book,
   Write-Once applications (12cm CD) seem to be slowly replacing applications in the WORM arena--
   which was expected.

Yellow Book

   Published by Philips and Sony, in l983, in a binder with yellow covers, the 'Yellow Book' used the Red
   Book as its basis to detail the physical specifications for the sectors in a CD-ROM--designed for
   computer data. The Yellow Book specified two types of sector layout (Mode 1 and Mode 2), additional
   'layered' error detection and correction to insure higher integrity of the contents, and much more. CD-
   ROM-XA is defined in supplements to the Yellow Book. In 1989, the Yellow Book was issued by the
   ISO as ISO/IEC 10149, Data Interchange on Read-Only 120mm Optical Discs (CD-ROM).

				
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