A CD-ROM (/ˌsiːdiːˈrɒm/, compact disc read-only memory) is a pre-pressed optical compact disc that contains data. Computers can read—but not write to or erase—CD-ROMs, i.e. it is a type of read-only memory.

During the 1990s, CD-ROMs were popularly used to distribute software and data for computers and fourth generation video game consoles. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data (such as software or digital video) is only usable on a computer (such as ISO 9660[2] format PC CD-ROMs).

The CD-ROM format was developed by Japanese company Denon in 1982. It was an extension of Compact Disc Digital Audio, and adapted the format to hold any form of digital data, with a storage capacity of 553 MiB.[3] CD-ROM was then introduced by Denon and Sony at a Japanese computer show in 1984.[4] The Yellow Book is the technical standard that defines the format of CD-ROMs. One of a set of color-bound books that contain the technical specifications for all CD formats, the Yellow Book, standardized by Sony and Philips in 1983, specifies a format for discs with a maximum capacity of 650 MiB.

A traditional CD-ROM
Media typeOptical disc
Capacity194 MiB (8 cm), 650–900 MiB (12 cm)
Read mechanism600-780nm laser diode, 150 KiB/s (1×), 10,800 KiB/s (72×)
Write mechanismPressed mold
StandardISO/IEC 10149[1]
UsageData storage

CD-ROM discs


CD-ROM Drive (Dell)
A CD-ROM in the tray of a partially open DVD-ROM drive.

CD-ROMs are identical in appearance to audio CDs, and data are stored and retrieved in a very similar manner (only differing from audio CDs in the standards used to store the data). Discs are made from a 1.2 mm thick disc of polycarbonate plastic, with a thin layer of aluminium to make a reflective surface. The most common size of CD-ROM is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as shaped compact discs in numerous non-standard sizes and molds (e.g., business card-sized media), are also available.

Data is stored on the disc as a series of microscopic indentations. A laser is shone onto the reflective surface of the disc to read the pattern of pits and lands ("pits", with the gaps between them referred to as "lands"). Because the depth of the pits is approximately one-quarter to one-sixth of the wavelength of the laser light used to read the disc, the reflected beam's phase is shifted in relation to the incoming beam, causing destructive interference and reducing the reflected beam's intensity. This is converted into binary data.


Several formats are used for data stored on compact discs, known as the Rainbow Books. The Yellow Book, published in 1988,[5] defines the specifications for CD-ROMs, standardized in 1989 as the ISO/IEC 10149 / ECMA-130 standard. The CD-ROM standard builds on top of the original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs, further define formats based on the CD-ROM specifications. The Yellow Book itself is not freely available, but the standards with the corresponding content can be downloaded for free from ISO[1] or ECMA.[6]

There are several standards that define how to structure data files on a CD-ROM. ISO 9660 defines the standard file system for a CD-ROM. ISO 13490 is an improvement on this standard which adds support for non-sequential write-once and re-writeable discs such as CD-R and CD-RW, as well as multiple sessions. The ISO 13346 standard was designed to address most of the shortcomings of ISO 9660,[7] and a subset of it evolved into the UDF format, which was adopted for DVDs. The bootable CD specification was issued in January 1995, to make a CD emulate a hard disk or floppy disk, and is called El Torito.

CD-ROM format

Data stored on CD-ROMs follows the standard CD data encoding techniques described in the Red Book specification (originally defined for audio CD only). This includes cross-interleaved Reed–Solomon coding (CIRC), eight-to-fourteen modulation (EFM), and the use of pits and lands for coding the bits into the physical surface of the CD.

The structures used to group data on a CD-ROM are also derived from the Red Book. Like audio CDs (CD-DA), a CD-ROM sector contains 2,352 bytes of user data, composed of 98 frames, each consisting of 33-bytes (24 bytes for the user data, 8 bytes for error correction, and 1 byte for the subcode). Unlike audio CDs, the data stored in these sectors corresponds to any type of digital data, not audio samples encoded according to the audio CD specification. To structure, address and protect this data, the CD-ROM standard further defines two sector modes, Mode 1 and Mode 2, which describe two different layouts for the data inside a sector.[2] A track (a group of sectors) inside a CD-ROM only contains sectors in the same mode, but if multiple tracks are present in a CD-ROM, each track can have its sectors in a different mode from the rest of the tracks. They can also coexist with audio CD tracks as well, which is the case of mixed mode CDs.

Both Mode 1 and 2 sectors use the first 16 bytes for header information, but differ in the remaining 2,336 bytes due to the use of error correction bytes. Unlike an audio CD, a CD-ROM cannot rely on error concealment by interpolation; a higher reliability of the retrieved data is required. To achieve improved error correction and detection, Mode 1, used mostly for digital data, adds a 32-bit cyclic redundancy check (CRC) code for error detection, and a third layer of Reed–Solomon error correction[n 1] using a Reed-Solomon Product-like Code (RSPC). Mode 1 therefore contains 288 bytes per sector for error detection and correction, leaving 2,048 bytes per sector available for data. Mode 2, which is more appropriate for image or video data (where perfect reliability may be a little bit less important), contains no additional error detection or correction bytes, having therefore 2,336 available data bytes per sector. Note that both modes, like audio CDs, still benefit from the lower layers of error correction at the frame level.[8]

Before being stored on a disc with the techniques described above, each CD-ROM sector is scrambled to prevent some problematic patterns from showing up.[6] These scrambled sectors then follow the same encoding process described in the Red Book in order to be finally stored on a CD.

The following table shows a comparison of the structure of sectors in CD-DA and CD-ROMs:[6]

Format ← 2,352 byte sector structure →
CD digital audio: 2,352 (Digital audio)
CD-ROM Mode 1: 12 (Sync pattern) 3 (Address) 1 (Mode, 0x01) 2,048 (Data) 4 (Error detection) 8 (Reserved, zero) 276 (Error correction)
CD-ROM Mode 2: 12 (Sync pattern) 3 (Address) 1 (Mode, 0x02) 2,336 (Data)

The net byte rate of a Mode-1 CD-ROM, based on comparison to CD-DA audio standards, is 44,100 Hz × 16 bits/sample × 2 channels × 2,048 / 2,352 / 8 = 153.6 kB/s = 150 KiB/s. This value, 150 KiB/s, is defined as "1× speed". Therefore, for Mode 1 CD-ROMs, a 1× CD-ROM drive reads 150/2 = 75 consecutive sectors per second.

The playing time of a standard CD is 74 minutes, or 4,440 seconds, contained in 333,000 blocks or sectors. Therefore, the net capacity of a Mode-1 CD-ROM is 682 MB or, equivalently, 650 MiB. For 80 minute CDs, the capacity is 737 MB (703 MiB).

CD-ROM XA extension

CD-ROM XA is an extension of the Yellow Book standard for CD-ROMs that combines compressed audio, video and computer data, allowing all to be accessed simultaneously.[9] It was intended as a bridge between CD-ROM and CD-i (Green Book) and was published by Sony and Philips in 1991.[5] "XA" stands for eXtended Architecture.

CD-ROM XA defines two new sector layouts, called Mode 2 Form 1 and Mode 2 Form 2 (which are different from the original Mode 2). XA Mode 2 Form 1 is similar to the Mode 1 structure described above, and can interleave with XA Mode 2 Form 2 sectors; it is used for data. XA Mode 2 Form 2 has 2,324 bytes of user data, and is similar to the standard Mode 2 but with error detection bytes added (though no error correction). It can interleave with XA Mode 2 Form 1 sectors, and it is used for audio/video data.[8] Video CDs, Super Video CDs, Photo CDs, Enhanced Music CDs and CD-i use these sector modes.[10]

The following table shows a comparison of the structure of sectors in CD-ROM XA modes:

Format ← 2,352 byte sector structure →
CD-ROM XA Mode 2, Form 1: 12 (Sync pattern) 3 (Address) 1 (Mode) 8 (Subheader) 2,048 (Data) 4 (Error detection) 276 (Error correction)
CD-ROM XA Mode 2, Form 2: 12 (Sync pattern) 3 (Address) 1 (Mode) 8 (Subheader) 2,324 (Data) 4 (Error detection)

Disc images

When a disc image of a CD-ROM is created, this can be done in either "raw" mode (extracting 2,352 bytes per sector, independent of the internal structure), or obtaining only the sector's useful data (2,048/2,336/2,352/2,324 bytes depending on the CD-ROM mode). The file size of a disc image created in raw mode is always a multiple of 2,352 bytes (the size of a block).[11] Disc image formats that store raw CD-ROM sectors include CCD/IMG, CUE/BIN, and MDS/MDF. The size of a disc image created from the data in the sectors will depend on the type of sectors it is using. For example, if a CD-ROM mode 1 image is created by extracting only each sector's data, its size will be a multiple of 2,048; this is usually the case for ISO disc images.

On a 74-minute CD-R, it is possible to fit larger disc images using raw mode, up to 333,000 × 2,352 = 783,216,000 bytes (~747 MiB). This is the upper limit for raw images created on a 74 min or ≈650 MiB Red Book CD. The 14.8% increase is due to the discarding of error correction data.


Pre-pressed CD-ROMs are mass-produced by a process of stamping where a glass master disc is created and used to make "stampers", which are in turn used to manufacture multiple copies of the final disc with the pits already present. Recordable (CD-R) and rewritable (CD-RW) discs are manufactured by a different method, whereby the data are recorded on them by a laser changing the properties of a dye or phase transition material in a process that is often referred to as "burning".


Print vs. bytes
A CD-ROM can easily store the entirety of a paper encyclopedia's words and images, plus audio & video clips

CD-ROM capacities are normally expressed with binary prefixes, subtracting the space used for error correction data. A standard 120 mm, 700 MB CD-ROM can actually hold about 737 MB (703 MiB) of data with error correction (or 847 MB total). In comparison, a single-layer DVD-ROM can hold 4.7 GB of error-protected data, more than 6 CD-ROMs.

Capacities of Compact Disc types (90 and 99 minute discs are not standard)
Type Sectors Data (mode 1) max. size Audio max. size Time
(MB) Approx. (MiB) (MB) (min)
8 cm 94,500 193.536 184.570 222.264 21
283,500 580.608 553.711 666.792 63
650 MB 333,000 681.984 650.391 783.216 74
700 MB 360,000 737.280 703.125 846.720 80
800 MB 405,000 829.440 791.016 952.560 90
900 MB 445,500 912.384 870.117 1,047.816 99
Note: megabyte (MB) and minute (min) values are exact; MiB values are approximate.

CD-ROM drives

CD laser assembly1
A view of a CD-ROM drive's disassembled laser system
The movement of the laser enables reading at any position of the CD
CD-Rom-Drive's Laser
The laser system of a CD-ROM drive

CD-ROM discs are read using CD-ROM drives. A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, SATA, FireWire, or USB interface or a proprietary interface, such as the Panasonic CD interface, LMSI/Philips, Sony and Mitsumi standards. Virtually all modern CD-ROM drives can also play audio CDs (as well as Video CDs and other data standards) when used with the right software.

Laser and optics

CD-ROM drives employ a near-infrared 780 nm laser diode. The laser beam is directed onto the disc via an opto-electronic tracking module, which then detects whether the beam has been reflected or scattered.

Transfer rates

CD-ROM drives are rated with a speed factor relative to music CDs. If a CD-ROM is read at the same rotational speed as an audio CD, the data transfer rate is 150 KiB/s, commonly called "1×". At this data rate, the track moves along under the laser spot at about 1.2 m/s. To maintain this linear velocity as the optical head moves to different positions, the angular velocity is varied from 500 rpm at the inner edge to 200 rpm at the outer edge. The 1× speed rating for CD-ROM (150 KiB/s) is different from the 1× speed rating for DVDs (1.32 MiB/s).

By increasing the speed at which the disc is spun, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8× speed spins the disc at 1600 to 4000 rpm, giving a linear velocity of 9.6 m/s and a transfer rate of 1200 KiB/s. Above 12× speed most drives read at Constant angular velocity (CAV, constant rpm) so that the motor is not made to change from one speed to another as the head seeks from place to place on the disc. In CAV mode the "×" number denotes the transfer rate at the outer edge of the disc, where it is a maximum. 20× was thought to be the maximum speed due to mechanical constraints until Samsung Electronics introduced the SCR-3230, a 32x CD-ROM drive which uses a ball bearing system to balance the spinning disc in the drive to reduce vibration and noise. As of 2004, the fastest transfer rate commonly available is about 52× or 10,400 rpm and 7.62 MiB/s. Higher spin speeds are limited by the strength of the polycarbonate plastic of which the discs are made. At 52×, the linear velocity of the outermost part of the disc is around 65 m/s. However, improvements can still be obtained using multiple laser pickups as demonstrated by the Kenwood TrueX 72× which uses seven laser beams and a rotation speed of approximately 10×.

The first 12× drive was released in late 1996.[12] Above 12× speed, there are problems with vibration and heat. CAV drives give speeds up to 30× at the outer edge of the disc with the same rotational speed as a standard constant linear velocity (CLV) 12×, or 32× with a slight increase. However, due to the nature of CAV (linear speed at the inner edge is still only 12×, increasing smoothly in-between) the actual throughput increase is less than 30/12: in fact, roughly 20× average for a completely full disc, and even less for a partially filled one.

Problems with vibration, owing to limits on achievable symmetry and strength in mass-produced media, mean that CD-ROM drive speeds have not massively increased since the late 1990s. Over 10 years later, commonly available drives vary between 24× (slimline and portable units, 10× spin speed) and 52× (typically CD- and read-only units, 21× spin speed), all using CAV to achieve their claimed "max" speeds, with 32× through 48× most common. Even so, these speeds can cause poor reading (drive error correction having become very sophisticated in response) and even shattering of poorly made or physically damaged media, with small cracks rapidly growing into catastrophic breakages when centripetally stressed at 10,000–13,000 rpm (i.e. 40–52× CAV). High rotational speeds also produce undesirable noise from disc vibration, rushing air and the spindle motor itself. Most 21st-century drives allow forced low speed modes (by use of small utility programs) for the sake of safety, accurate reading or silence, and will automatically fall back if numerous sequential read errors and retries are encountered.

Other methods of improving read speed were trialled such as using multiple optical beams, increasing throughput up to 72× with a 10× spin speed, but along with other technologies like 90~99 minute recordable media and "double density" recorders, their utility was nullified by the introduction of consumer DVD-ROM drives capable of consistent 36× CD-ROM speeds (4× DVD) or higher. Additionally, with a 700 MB CD-ROM fully readable in under 2½ minutes at 52× CAV, increases in actual data transfer rate are decreasingly influential on overall effective drive speed when taken into consideration with other factors such as loading/unloading, media recognition, spin up/down and random seek times, making for much decreased returns on development investment. A similar stratification effect has since been seen in DVD development where maximum speed has stabilised at 16× CAV (with exceptional cases between 18× and 22×) and capacity at 4.3 and 8.5 GiB (single and dual layer), with higher speed and capacity needs instead being catered to by Blu-ray drives.

CD-Recordable drives are often sold with three different speed ratings, one speed for write-once operations, one for re-write operations, and one for read-only operations. The speeds are typically listed in that order; i.e. a 12×/10×/32× CD drive can, CPU and media permitting, write to CD-R discs at 12× speed (1.76 MiB/s), write to CD-RW discs at 10× speed (1.46 MiB/s), and read from CDs at 32× speed (4.69 MiB/s).

Common data transfer speeds for CD-ROM drives
Transfer speed KiB/s Mbit/s MiB/s [n 2] RPM
150 1.2288 0.146 200–500
300 2.4576 0.293 400-1,000
600 4.9152 0.586 800–2,000
1,200 9.8304 1.17 1,600–4,000
10× 1,500 12.288 1.46 2,000–5,000
12× 1,800 14.7456 1.76 2,400–6,000
20× 1,200–3,000 up to 24.576 up to 2.93 4,000 (CAV)
32× 1,920–4,800 up to 39.3216 up to 4.69 6,400 (CAV)
36× 2,160–5,400 up to 44.2368 up to 5.27 7,200 (CAV)
40× 2,400–6,000 up to 49.152 up to 5.86 8,000 (CAV)
48× 2,880–7,200 up to 58.9824 up to 7.03 9,600 (CAV)
52× 3,120–7,800 up to 63.8976 up to 7.62 10,400 (CAV)
56× 3,360–8,400 up to 68.8128 up to 8.20 11,200 (CAV)
72× 6,750–10,800 up to 88.4736 up to 10.5 2,000 (multi-beam)

Copyright issues

Software distributors, and in particular distributors of computer games, often make use of various copy protection schemes to prevent software running from any media besides the original CD-ROMs. This differs somewhat from audio CD protection in that it is usually implemented in both the media and the software itself. The CD-ROM itself may contain "weak" sectors to make copying the disc more difficult, and additional data that may be difficult or impossible to copy to a CD-R or disc image, but which the software checks for each time it is run to ensure an original disc and not an unauthorized copy is present in the computer's CD-ROM drive.

Manufacturers of CD writers (CD-R or CD-RW) are encouraged by the music industry to ensure that every drive they produce has a unique identifier, which will be encoded by the drive on every disc that it records: the RID or Recorder Identification Code.[13] This is a counterpart to the Source Identification Code (SID), an eight character code beginning with "IFPI" that is usually stamped on discs produced by CD recording plants.

See also


  1. ^ Note that the CIRC error correction system used in the CD audio format has two interleaved layers.
  2. ^ To three significant figures.


  1. ^ a b ISO (1995). "ISO/IEC 10149:1995 – Information technology – Data interchange on read-only 120 mm optical data disks (CD-ROM)". Retrieved 2010-08-06.
  2. ^ a b "CD Yellow Book Standards". Retrieved 2015-11-16.
  3. ^ Videodisc Update, Volumes 1-3, page 13, 1982
  4. ^ Japanese PCs (1984) (14:24), Computer Chronicles
  5. ^ a b "What is Yellow Book?". Retrieved 2013-09-23.
  6. ^ a b c "Data Interchange on Read-only 120 mm Optical Data Disks (CD-ROM)". ECMA. June 1996. Retrieved 2009-04-26.
  7. ^ "Birth Announcement: ISO/IEC 13346 and ISO/IEC 13490". Retrieved 2013-09-23.
  8. ^ a b McFadden, Andy (2002-12-20). "What is XA? CDPLUS? CD-i? MODE1 vs MODE2? Red/yellow/blue book?". CD-Recordable FAQ. Retrieved 2008-05-04.
  9. ^ What are CD-ROM Mode-1, Mode-2 and XA? Archived 2013-01-26 at the Wayback Machine., Sony Storage Support
  10. ^ "Gateway Support - What is CD-ROM/XA?". Retrieved 2013-09-23.
  11. ^ "Optical Media FAQs" (PDF). Archived from the original (PDF) on 2006-10-22. Retrieved 2007-01-06.
  12. ^ "Gadget". Next Generation. No. 25. Imagine Media. January 1997. p. 30. Here comes Diamond with the first 12X CD-ROM.
  13. ^ Schoen, Seth (July 20, 2007). "Harry Potter and the Digital Fingerprints". Electronic Frontier Foundation. Retrieved October 24, 2007.
Amiga CD32

The Amiga CD32, styled Amiga CD32 and code-named "Spellbound", is a 32 bit home video game console developed by Commodore and released in western Europe, Australia, Canada and Brazil. It was first announced at the Science Museum in London on July 16, 1993, and was released in September of the same year.

The CD32 is part of a family of Amiga computers and other hardware. It uses CD-ROM as its storage medium. It was based on Commodore's Advanced Graphics Architecture chipset, and is of similar specification to the Amiga 1200 computer. Using third party devices, it is possible to upgrade the CD32 with keyboard, floppy drive, hard drive, RAM and mouse, turning it into the equivalent of an Amiga 1200 personal computer. A hardware MPEG decompression module for playing Video CD was also released.

In the Christmas period following its launch, the CD32 accounted for 38% of all CD-ROM drive sales in the UK, exceeding sales of the Mega-CD; however, it was soon overshadowed by CD-ROM based games consoles from other companies, and was discontinued as Commodore went into bankruptcy.

Apple Bandai Pippin

The Apple Bandai Pippin, stylized PiP P!N, is a multimedia technology console, designed by Apple Computer. The console was based on the Apple Pippin platform – a derivative of the Apple Macintosh platform. Bandai produced the ATMARK and @WORLD consoles between 1996 and 1997.

The goal of the Bandai Pippin was to create an inexpensive computer system aimed mostly at playing CD-based multimedia software, especially games, but also functioning as a thin client. The operating system was a version of System 7.5.2, and was based on a 66 MHz PowerPC 603 processor and a 14.4 kb/s modem. It featured a 4×-speed CD-ROM drive and a video output that could connect to a standard television display.

Blender (magazine)

Blender was an American music magazine that billed itself as "the ultimate guide to music and more". It was also known for sometimes steamy pictorials of celebrities. It compiled lists of albums, artists, and songs, including both "best of" and "worst of" lists. In each issue, there was a review of an artist's entire discography, with each album being analyzed in turn.

Blender was published by Dennis Publishing. The magazine began in 1994 as the first digital CD-ROM magazine by Jason Pearson, David Cherry, and Regina Joseph, acquired by Felix Dennis/Dennis Publishing, UK it published 15 digital CD issues, and launched on the web in 1997. It started publishing a print edition again in 1999 in its most recent form. Blender CD-ROM showcased the earliest digital editorial formats, as well as the first forms of digital advertising. The first digital advertisers included Calvin Klein, Apple Computer, Toyota and Nike.

In June 2006, the Chicago Tribune named it one of the top ten English-language magazines, describing it as "the cool kid at the school of rock magazines".Owner Alpha Media Group closed Blender magazine March 26, 2009, going to an online-only format in a move that eliminated 30 jobs and reduced the company's portfolio of titles to Maxim alone. Blender's final print issue was the April 2009 issue. Subscribers to the magazine were sent issues of Maxim magazine to make up for the unsent Blender issues.

CD-ROM Today

CD-ROM Today was an American magazine targeted at computer users. Published from 1993 to 1996 by Imagine Publishing (now Future US), the magazine was initially issued once every other month, before becoming a monthly. Each issue included software and hardware reviews, as well as a CD containing fonts, video and text files, system updaters, freeware and shareware and demo versions of commercial software. Products were included for both Macintosh and Windows PC.

CD-ROM Today was the highest-selling review magazine for both Macintosh and PC users in 1996. In 1996, after four seasonal and 25 numbered issues, the magazine was discontinued, with two newer publications replacing it: MacAddict for Macintosh users, and boot for Windows users. Both magazines were first issued in August 1996 and have since been renamed MacLife and Maximum PC, respectively.


Cinepak is a lossy video codec developed by Peter Barrett at SuperMac Technologies, and released in 1991 with the Video Spigot, and then in 1992 as part of Apple Computer's QuickTime video suite. One of the first video compression tools to achieve full motion video on CD-ROM, it was designed to encode 320×240 resolution video at 1× (150 kbyte/s) CD-ROM transfer rates. The original name of this codec was CompactVideo, which is why its FourCC identifier is CVID. The codec was ported to the Microsoft Windows platform in 1993. It was also used on first-generation and some second-generation CD-ROM game consoles, such as the Atari Jaguar CD, Sega CD, Sega Saturn, and 3DO. libavcodec includes a Cinepak decoder and an encoder, both licensed under the terms of the LGPL.

El Torito (CD-ROM standard)

The El Torito Bootable CD Specification is an extension to the ISO 9660 CD-ROM specification. It is designed to allow a computer to boot from a CD-ROM. It was announced in November 1994 and first issued in January 1995 as a joint proposal by IBM and BIOS manufacturer Phoenix Technologies.

Encyclopedia of Mathematics

The Encyclopedia of Mathematics (also EOM and formerly Encyclopaedia of Mathematics) is a large reference work in mathematics. It is available in book form and on CD-ROM.

Enhanced CD

Enhanced CD is a certification mark of the Recording Industry Association of America for various technologies that combine audio and computer data for use in both Compact Disc and CD-ROM players.Formats that fall under the "enhanced CD" category include mixed mode CD (Yellow Book CD-ROM/Red Book CD-DA), CD-i, CD-i Ready, and CD-Extra/CD-Plus (Blue Book, also called simply Enhanced Music CD or E-CD).The technology was popular in the late 1990s with the increase of computer usage. Music CDs often included music videos, wallpapers, and other various content. However, more recently, acts wishing to include enhanced content often include a DVD instead, with the disadvantage of it not playing in a CD audio player, but with the advantage of storing greater amounts of data and/or higher-quality video.


Grolier is one of the largest U.S. publishers of general encyclopedias, including The Book of Knowledge (1910), The New Book of Knowledge (1966), The New Book of Popular Science (1972), Encyclopedia Americana (1945), Academic American Encyclopedia (1980), and numerous incarnations of a CD-ROM encyclopedia (1986–2003).

Grolier is an educational publishing company known for its presence in school libraries. It has a strong presence among parents of children under six years old, the target of Grolier's direct mail-to-the-home business.In June 2000 Grolier became part of Scholastic Corporation, which now maintains Grolier Online.

High Sierra Format

High Sierra Format (HSF) is the early logical file system used for CD-ROMs in 1985 and 1986. The later ECMA-119 and ISO 9660 standards are based on revised HSF.

ISO 13490

ISO/IEC 13490 (also known as ECMA-168) is the successor to ISO 9660 (level 3), intended to describe the file system of a CD-ROM or CD-R.

ISO 13490 has several improvements over its predecessor. It fully addresses the filename, POSIX attribute, and multibyte character issues that were not handled by ISO 9660. It is also a more efficient format, permits incremental recording, and permits both the ISO 9660 format and ISO/IEC 13490 format to co-exist on the same media. It also specifies how to use multisession properly.

It is derived from the Frankfurt Group (formed in 1990 by many CD-ROM and CD-WO hardware and media manufacturers, CD-ROM data publishers, users of CD-ROMs, and major computer companies) proposal and fully supports orange book media.

Irish Statute Book

The Irish Statute Book, also known as the electronic Irish Statute Book (eISB), is a database produced by the Office of the Attorney General of Ireland. It contains copies of Acts of the Oireachtas and statutory instruments. It also contains a Legislation Directory which includes chronological tables of pre-1922 legislation. It is published on a website ( and was formerly published on CD-ROM.In 2001, the Irish Law Times said that whilst the Attorney General's staff deserved to be congratulated for the Irish Statute Book, the CD-ROM version contained a "significant number of errors".

List of PC Engine games

The following is a list of video games released for the PC Engine video game console in Japan - released as the TurboGrafx-16 in North America (see List of TurboGrafx-16 games). A total of 650 video games were officially released commercially for the console between its launch on October 10, 1987, up until June 3, 1999.

PC Engine games were released in two types of storage formats, HuCards and CD-ROMs, with varying level of compatibility depending on the hardware configurations and options available. Specifically, there are two types of HuCard formats (the standard HuCards that comprised the majority of the PC Engine's library and a handful of titles that are playable only on the PC Engine SuperGrafx) and three types of CD-ROM formats (CD-ROM², Super CD-ROM² and Arcade CD-ROM², each requiring the console to be equipped with a CD drive and the corresponding System Card if needed). There were also dual-compatible games that were designed to run in an older hardware specifications, but are programmed to take advantage of a newer one (such as reduced loading times).


MSCDEX or Microsoft CD-ROM Extensions is a software program produced by Microsoft and included with MS-DOS 6.x and certain versions of Microsoft Windows. Earlier versions of MSCDEX since 1986 were installable add-ons for MS-DOS 3.1 and higher.It is a driver executable which allows DOS programs to recognize, read, and control CD-ROMs using the High Sierra and - since version 2.0 as of 1988 - also the ISO 9660 file systems. This requires the previous loading of an appropriate CD-ROM device driver (example: OAKCDROM.SYS), usually from CONFIG.SYS.

The final version of the MSCDEX program was 2.96, included with Windows 95 and used when creating bootable floppy disks with CD-ROM support. Starting with Windows 95, CD-ROM access became possible through a 32-bit CDFS driver.

The driver uses the Microsoft networks interface in MS-DOS. This is the reason that at least version 3.1 of MS-DOS is required. The driver essentially looks similar to a network drive from the system perspective. It is implemented as a TSR program and an extension to the redirector interface (CDEX).

Mini CD

Mini CDs, or pocket CDs, are CDs with a smaller diameter and one third the storage capacity of a standard 120 mm disc.


NewsBank is a news database resource which provides archives of media publications as reference materials to libraries.

Optical disc drive

In computing, an optical disc drive (ODD) is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives. Optical disc drives that are no longer in production include CD-ROM drive, CD writer drive, combo (CD-RW/DVD-ROM) drive, and DVD writer drive supporting certain recordable and rewritable DVD formats (such as DVD-R(W) only, DVD+R(W) only, DVD-RAM only, and all DVD formats except DVD-R DL). As of 2015, DVD writer drive supporting all existing recordable and rewritable DVD formats is the most common for desktop PCs and laptops. There are also the DVD-ROM drive, BD-ROM drive, Blu-ray Disc combo (BD-ROM/DVD±RW/CD-RW) drive, and Blu-ray Disc writer drive.

Optical disc drives are an integral part of standalone appliances such as CD players, DVD players, Blu-ray disc players, DVD recorders, certain desktop video game consoles, such as Sony PlayStation 4, Microsoft Xbox One, Nintendo Wii U, and Sony PlayStation 3, and certain portable video game consoles, such as Sony PlayStation Portable. They are also very commonly used in computers to read software and consumer media distributed on disc, and to record discs for archival and data exchange purposes. Floppy disk drives, with capacity of 1.44 MB, have been made obsolete: optical media are cheap and have vastly higher capacity to handle the large files used since the days of floppy discs, and the vast majority of computers and much consumer entertainment hardware have optical writers. USB flash drives, high-capacity, small, and inexpensive, are suitable where read/write capability is required.

Disc recording is restricted to storing files playable on consumer appliances (films, music, etc.), relatively small volumes of data (e.g. a standard DVD holds 4.7 gigabytes) for local use, and data for distribution, but only on a small scale; mass-producing large numbers of identical discs is cheaper and faster than individual recording.

Optical discs are used to back up relatively small volumes of data, but backing up of entire hard drives, which as of 2015 typically contain many hundreds of gigabytes or even multiple terabytes, is less practical. Large backups are often instead made on external hard drives, as their price has dropped to a level making this viable; in professional environments magnetic tape drives are also used.


The Super NES CD-ROM System (commonly shortened as the SNES-CD), also known as the Super Famicom CD-ROM Adapter, is an unreleased video game peripheral for the Super Nintendo Entertainment System (SNES). The add-on built upon the functionality of the cartridge-based SNES by adding support for a CD-ROM-based format known as Super Disc.The SNES-CD platform was developed in a partnership between Nintendo and Sony. The platform was planned to be launched as an add-on for the standard SNES, as well as a hybrid console by Sony called the PlayStation (nicknamed the "Nintendo PlayStation" to distinguish it from the later Sony console of the same name). Another partnership with Philips yielded some poorly received Nintendo-themed games for the CD-i platform instead of the SNES-CD. Sony independently furthered its developments into their own stand-alone console of the same name, which served as the chief competitor of the Super NES's cartridge-based successor, the Nintendo 64.


The TurboGrafx-16 Entertainment SuperSystem, known in Japan and France as the PC Engine (PCエンジン, Pī Shī Enjin), is a cartridge based home video game console manufactured and marketed by NEC Home Electronics, and designed by Hudson Soft. It was released in Japan on October 30, 1987 and in the United States on August 29, 1989. It also had a limited release in the United Kingdom and Spain in 1990, known as simply TurboGrafx and based on the American model, while the Japanese model was imported and distributed in France in 1989. It was the first console released in the 16-bit era, although it used an 8-bit CPU. Originally intended to compete with the Nintendo Entertainment System (NES), it ended up competing with the Sega Genesis, and later on the Super Nintendo Entertainment System (SNES).

The TurboGrafx-16 has an 8-bit CPU, a 16-bit video color encoder, and a 16-bit video display controller. The GPUs are capable of displaying 482 colors simultaneously, out of 512. With dimensions of just 14 cm × 14 cm × 3.8 cm (5.5 in × 5.5 in × 1.5 in), the Japanese PC Engine is the smallest major home game console ever made. Games were stored on a HuCard cartridge, or in CD-ROM optical format with the TurboGrafx-CD add-on.

The TurboGrafx-16 failed to break into the North American market and sold poorly, which has been blamed on inferior marketing. Despite the "16" in its name and the marketing of the console as a 16-bit platform, it used an 8-bit CPU, a marketing tactic that was criticized by some as deceptive. Developer Doug Snook of ICOM Simulations said the CPU was a performance problem.However, in Japan, the PC Engine, introduced into the market at a much earlier date, was very successful, where it gained strong third-party support and outsold the Famicom at its 1987 debut, eventually becoming the Super Famicom's main rival. Lots of revisions - at least 17 distinct models - were made, such as portable versions and a CD-ROM add-on. An enhanced model, the PC Engine SuperGrafx, was intended to supersede the standard PC Engine, but failed to break through and was quickly discontinued. The entire series was succeeded by the PC-FX in 1994, only released in Japan.

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