A play on the word 'archive', it is a distributed database of archive files.
An education and research network that makes up part of the Internet, mainly used for email & listservs.
A measurement of a network's transmission speed, how much data a network can transfer in a given
amount of time?
The number of transitions per second made by a modem.
Bits per second (BPS)
Measurement of the data transmission for a modem or network.
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.
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.
Two computer systems linked by a network or modem connection where the client computer uses
resources by sending requests to the server computer.
A collection of information stored oftentimes in a computerized format. Examples: library catalogs, search
engines, financial data, etc.
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.
The name of a computer or server on the Internet in the form of a string of names or numbers, separated
The transfer a file or files from a remote computer to the user's computer.
Abbreviation for Domain Name System. A distributed client-server database system which links domain
names with their numerical IP addresses.
Abbreviation for electronic mail. A letter or memo sent to a person or group electronically on the Internet.
A user's electronic mailbox name or address, needed for linking the sender of e-mail and the recipient.
Abbreviation for Frequently Asked Questions. A document (often a hypertext document) containing
common questions and answers for a particular website or topic.
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.
Internet service that provides information about the users on a particular computer.
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.
A computer system that connects two incompatible services such as a commercial online service and the
Graphical Interchange Format is a commonly used graphics file format for image files on the Internet.
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.
The main page of hypertext-based information for n individual or organization on the World Wide Web
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.
Abbreviation for Hyper Text Transfer Protocol. Often this is the initial sequence of letters in a web
A system for storing information using embedded references to other pages, sounds, and graphics used
on the WWW.
The text-based version of hypermedia.
Slang for someone who is an experienced Internet user.
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
Abbreviation for Internet Protocol. A protocol that ensures data goes where it is supposed to go on the
Abbreviation for Internet Relay Chat. An Internet service accessed through software programs that
features real-time communication on channels devoted to specific topics.
Abbreviation for Local Area Network. Used to connect computers over a short distance such as
computers within the same company or office.
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
The process entering in information related to an account name and its password in order to access a
An e-mail system that includes multiple recipients as part of its address. See e-mail.
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
Slang for someone who is new to the Internet or a specific aspect of it.
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.
The unwritten "rules" of etiquette used on the Internet.
A graphical World Wide Web browser for Macintosh, Microsoft Windows, and Amiga systems.
A set of computers that all use the same protocol in order to exchange information among themselves.
Secret code of letters and numbers needed to gain access to a time-sharing computer or FTP system, or
to protect Web pages.
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.
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.
Abbreviation for Point to Point Protocol. It is a protocol used for sending information via a modem which is
connected to the Internet.
The rules make possible the exchange of messages between users on the Internet, or within any given
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.
A company that provides dial-up or direct access to the Internet for a fee. Sometimes referred to as ISP
(internet service provider).
Copyrighted software that is available for personal use for a small fee, and often downloadable from the
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.
Slang for regular, paper mail sent through the postal services.
Stands for Transmission Control Protocol. both the protocol and software that ensure that data sent over
the Net arrive in the correct order.
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.
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
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.
Transferring a file or files from the user's computer to a remote computer.
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.
A group of computers that exchange network news information.
An Internet tool that allows you to search by keyword through gopher titles and directories.
Short for Wide Area Information Server. An internet search service that locates documents containing a
keyword or phrase.
Stands for Wide Area Network. A network of computers that covers a large geographical distance.
An Internet database that provides information on a person or an organization.
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.
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.
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.
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.
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.).
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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,
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.
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.
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.
In computers, a bus is the main or continuous channel of electrical connection between the CPU, the
system memory (RAM), and the peripheral devices.
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.
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.
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.
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.
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.
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.
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.
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.
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 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.
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
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.
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
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.
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 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
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).
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.
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.
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.
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.
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.
Special material used to line or cover an optical fiber, to reflect and confine the light waves to the
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 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.
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.
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.
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
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
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.
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
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
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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 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.
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.
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.
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.).
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.
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
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.).
Digital Signal Processors are specialized processor chips used for diverse functions, especially in
modems, sound boards and serial ports.
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.
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.
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.
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.
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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
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.
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
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
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).
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.
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
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 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-
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.
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
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.
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.
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.
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.
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.
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.
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.
Kilobits per second (1000 bits/sec) is a measure used mainly in computer communications, for
transmission rates and hardware bandwidths.
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
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,
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.
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.
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.
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.
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
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-
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.
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 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.
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
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.
A Megabyte (MB) is 1024 KBytes, or 1,048,576 bytes.
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.
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.
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.
One millionth of a second.
An erasable optical disc, usually 8cm in diameter.
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.'
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.
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.
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.
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 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.
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.
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.
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
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.
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.
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.
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.
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
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.
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.
This is an operating system, implemented in microcomputers specifically for CD-I.
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.
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.
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
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.
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.
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
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
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.
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.
These are empty lengths of track (two seconds, or equivalent, of nothing but 0s), which are placed
before and after the data track.
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.'
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.
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
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
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.
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
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.
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.
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.
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
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.
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.
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.
Resource Interchange File Format is used to store multimedia files, because it also allows their use in
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.
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.
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 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 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.
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.
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.
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!
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.
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.
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.
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
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.
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.
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.
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.
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.
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
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
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
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'.
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.
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.
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.
In CDs, the sectors include an specific space allocated for data used by the application (user).
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.
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.
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.
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.
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.
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.
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.
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).