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91-465: SilverPlatter Information, Inc. was one of the first companies to produce commercial reference databases on CD-ROMs . It was founded in 1983 in the United Kingdom by Béla Hatvany and Walt Winshall with the explicit intention of using CD technology to publish data, and thus provide an alternative to searching databases in magnetic tape format. Ron Rietdyk was the company's first President. The firm

182-449: A 12×/10×/32× CD drive can write to CD-R discs at 12× speed (1.76 MB/s), write to CD-RW discs at 10× speed (1.46 MB/s), and read from CDs at 32× speed (4.69 MB/s), if the CPU and media player software permit speeds that high. 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

273-542: A BIOS drive number to the CD drive. The drive number (for INT 13H ) assigned is any of 80 hex ( hard disk emulation), 00 hex ( floppy disk emulation) or an arbitrary number if the BIOS should not provide emulation. Emulation is useful for booting older operating systems from a CD, by making it appear to them as if they were booted from a hard or floppy disk. UEFI systems also accept El Torito records, as platform 0xEF. The record

364-1095: A CD-ROM with Amiga extensions was MakeCD , an Amiga software which Angela Schmidt developed together with Patrick Ohly. El Torito is an extension designed to allow booting a computer 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 . According to legend, the El Torito CD/DVD extension to ISO 9660 got its name because its design originated in an El Torito restaurant in Irvine, California ( 33°41′05″N 117°51′09″W  /  33.684722°N 117.852547°W  / 33.684722; -117.852547 ). The initial two authors were Curtis Stevens, of Phoenix Technologies, and Stan Merkin, of IBM. A 32-bit PC BIOS will search for boot code on an ISO 9660 CD-ROM. The standard allows for booting in two different modes. Either in hard disk emulation when

455-416: 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, 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 ;

546-414: A block). 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

637-493: A different language opens a Romeo disk, the lack of code page indication will cause non-ASCII characters in file names to become Mojibake . For example, "ü" may become "³". A different OS may encounter a similar problem or refuse to recognize these noncompliant names outright. The same code page problem technically exists in standard ISO 9660, which allows open interpretation of the supplemental and enhanced volume descriptors to any character encoding subject to agreement. However,

728-421: A file attribute that indicates its nature (similar to Unix ). The attributes of a file are stored in the directory entry that describes the file, and optionally in the extended attribute record. To locate a file, the directory names in the file's path can be checked sequentially, going to the location of each directory to obtain the location of the subsequent subdirectory. However, a file can also be located through

819-466: 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 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

910-422: A new "enhanced volume descriptor" data structure. The standard was submitted for ISO 9660:1999 and supposedly fast-tracked, but nothing came out of it. Nevertheless, several operating systems and disc authoring tools (such as Nero Burning ROM , mkisofs and ImgBurn ) now support the addition, under such names as "ISO 9660:1999", "ISO 9660 v2", or "ISO 9660 Level 4". In 2013, the proposal was finally formalized in

1001-477: 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. 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

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1092-506: A separate system use area where future optional extensions for each file may be specified. High Sierra was adopted in December 1986 (with changes) as an international standard by Ecma International as ECMA-119 and submitted for fast tracking to the ISO , where it was eventually accepted as ISO 9660:1988. Subsequent amendments to the standard were published in 2013 and 2020 . The first 16 sectors of

1183-489: 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 ), also exist. Data

1274-463: Is a maximum. 20× was thought to be the maximum speed due to mechanical constraints until Samsung Electronics introduced the SCR-3230, a 32× 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 MB/s. Higher spin speeds are limited by the strength of

1365-491: Is an extension which adds POSIX file system semantics. The availability of these extension properties allows for better integration with Unix and Unix-like operating systems. The standard takes its name from the fictional town Rock Ridge in Mel Brooks ' film Blazing Saddles . The RRIP extensions are, briefly: The RRIP extensions are built upon SUSP, defining additional tags for support of POSIX semantics, along with

1456-578: 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 650 MB (650 × 2 ). For 80 minute CDs, the capacity is 703 MB. 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. It

1547-447: Is expected to be a disk image containing a FAT filesystem, the filesystem being an EFI System Partition containing the usual \EFI directory. The image should be marked for "no emulation", though it does not actually work like the BIOS "no emulation" mode, in which the BIOS would load the image in memory and execute the code from there. El Torito can also be used to produce CDs which can boot up Linux operating systems, by including

1638-418: 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. Both modes, like audio CDs, still benefit from the lower layers of error correction at the frame level. Before being stored on a disc with the techniques described above, each CD-ROM sector

1729-428: Is possible to fit larger disc images using raw mode, up to 333,000 × 2,352 = 783,216,000 bytes (~747 MB). This is the upper limit for raw images created on a 74 min or ≈650 MB Red Book CD. The 14.8% increase is due to the discarding of error correction data. CD-ROM capacities are normally expressed with binary prefixes , subtracting the space used for error correction data. The capacity of a CD-ROM depends on how close

1820-534: 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. This is a counterpart to the Source Identification Code (SID), an eight character code beginning with " IFPI " that

1911-593: Is scrambled to prevent some problematic patterns from showing up. 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: 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 = 150 KB/s (150 × 2 ) . This value, 150 Kbyte/s,

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2002-421: Is stored on the disc as a series of microscopic indentations called "pits", with the non-indented spaces between them called "lands". A laser is shone onto the reflective surface of the disc to read the pattern of pits and 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

2093-402: 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. Video CDs , Super Video CDs , Photo CDs , Enhanced Music CDs and CD-i use these sector modes. The following table shows a comparison of

2184-516: Is usually stamped on discs produced by CD recording plants. ISO 9660 ISO 9660 (also known as ECMA -119 ) is a file system for optical disc media. The file system is an international standard available from the International Organization for Standardization (ISO). Since the specification is available for anybody to purchase, implementations have been written for many operating systems . ISO 9660 traces its roots to

2275-481: The Apple ISO 9660 Extensions (file characteristics specific to the classic Mac OS and macOS , such as resource forks , file backup date and more). Compact discs were originally developed for recording musical data, but soon were used for storing additional digital data types because they were equally effective for archival mass data storage . Called CD-ROMs , the lowest level format for these type of compact discs

2366-478: The Apple ISO 9660 Extensions (file characteristics specific to the classic Mac OS and macOS , such as resource forks , file backup date and more). System Use Sharing Protocol (SUSP, IEEE P1281) provides a generic way of including additional properties for any directory entry reachable from the primary volume descriptor (PVD). In an ISO 9660 volume, every directory entry has an optional system use area whose contents are undefined and left to be interpreted by

2457-574: The GRUB bootloader on the CD and following the Multiboot Specification . While the El Torito spec alludes to a "Mac" platform ID, PowerPC-based Apple Macintosh computers don't use it. Joliet is an extension specified and endorsed by Microsoft and has been supported by all versions of its Windows operating system since Windows 95 and Windows NT 4.0 . Its primary focus is the relaxation of

2548-504: The High Sierra Format , which arranged file information in a dense, sequential layout to minimize nonsequential access by using a hierarchical (eight levels of directories deep) tree file system arrangement, similar to UNIX and FAT . To facilitate cross platform compatibility, it defined a minimal set of common file attributes (directory or ordinary file and time of recording) and name attributes (name, extension, and version), and used

2639-644: The ISO 9660 standard in 1988. One of the first products to be made available to the public on CD-ROM was the Grolier Academic Encyclopedia , presented at the Microsoft CD-ROM Conference in March 1986. CD-ROMs began being used in home video game consoles starting with the PC Engine CD-ROM (TurboGrafx-CD) in 1988, while CD-ROM drives had also become available for home computers by

2730-706: The Yellow Book CD-ROM standard, which was so open ended it was leading to diversification and creation of many incompatible data storage methods. The High Sierra Group Proposal ( HSGP ) was released in May 1986, defining a file system for CD-ROMs commonly known as the High Sierra Format. A draft version of this proposal was submitted to the European Computer Manufacturers Association (ECMA) for standardization. With some changes, this led to

2821-461: The volume descriptor set , a set of one or more volume descriptors terminated with a volume descriptor set terminator . These collectively act as a header for the data area, describing its content (similar to the BIOS parameter block used by FAT , HPFS and NTFS formatted disks). Each volume descriptor is 2048 bytes in size, fitting perfectly into a single Mode 1 or Mode 2 Form 1 sector. They have

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2912-432: The 1990s were called " multimedia " computers because they incorporated a CD-ROM drive, which allowed for the delivery of several hundred megabytes of video, picture, and audio data. The first laptop to have an integrated CD-ROM drive as an option was 1993's CF-V21P by Panasonic ; however, the drive only supported mini CDs up to 3.5 inches in diameter. The first notebook to support standard 4.7-inch-diameter discs

3003-446: The 4 GiB limit. For example, the free software such as InfraRecorder , ImgBurn and mkisofs as well as Roxio Toast are able to create ISO 9660 file systems that use multi-extent files to store files larger than 4 GiB on appropriate media such as recordable DVDs. Linux supports multiple extents. Since amendment 1 (or ECMA-119 3rd edition, or "JIS X 0606:1998 / ISO 9660:1999"), a much wider variety of file trees can be expressed by

3094-712: The DXP protocol. This last proved successful with more than 500 sites using the firm's technology by 1997. In that year the company had grown to $ 75m in revenues and had over 250 databases. In 2001, SilverPlatter was sold to Wolters Kluwer at a reputed price of $ 113m, and now forms part of Ovid Technologies , the Wolters Kluwer subsidiary. CD-ROM During the 1990s and early 2000s, CD-ROMs were popularly used to distribute software and data for computers and fifth generation video game consoles . DVDs as well as downloading started to replace CD-ROMs in these roles starting in

3185-615: The EVD system. There is no longer any character limit (even 8-bit characters are allowed), nor any depth limit or path length limit. There still is a limit on name length, at 207. The character set is no longer enforced, so both sides of the disc interchange need to agree via a different channel. There are several extensions to ISO 9660 that relax some of its limitations. Notable examples include Rock Ridge (Unix-style permissions and longer names), Joliet ( Unicode , allowing non- Latin scripts to be used), El Torito (enables CDs to be bootable ) and

3276-534: The High Sierra Format in the ECMA-119 and ISO 9660 standards were international extensions to allow the format to work better on non-US markets. In order not to create incompatibilities, NISO suspended further work on Z39.60, which had been adopted by NISO members on 28 May 1987. It was withdrawn before final approval, in favour of ISO 9660. JIS X 0606:1998 was passed in Japan in 1998 with much-relaxed file name rules using

3367-554: The additional Amiga -bits for files. There is support for attribute "P" that stands for "pure" bit (indicating re-entrant command) and attribute "S" for script bit (indicating batch file ). This includes the protection flags plus an optional comment field. These extensions were introduced by Angela Schmidt with the help of Andrew Young, the primary author of the Rock Ridge Interchange Protocol and System Use Sharing Protocol. The first publicly available software to master

3458-406: The beam has been reflected or scattered. 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 Kbyte/s, commonly called "1×" (with constant linear velocity, short "CLV" ). At this data rate, the track moves along under the laser spot at about 1.2 m/s. To maintain this linear velocity as

3549-588: The body of the standard: The depth of the directory hierarchy must not exceed 8 (root directory being at level 1), and the path length of any file must not exceed 255. (section 6.8.2.1). The standard also specifies the following name restrictions (sections 7.5 and 7.6): A CD-ROM producer may choose one of the lower Levels of Interchange specified in chapter 10 of the standard, and further restrict file name length from 30 characters to only 8+3 in file identifiers, and 8 in directory identifiers in order to promote interchangeability with implementations that do not implement

3640-426: The boot information can be accessed directly from the CD media, or in floppy emulation mode where the boot information is stored in an image file of a floppy disk , which is loaded from the CD and then behaves as a virtual floppy disk. This is useful for computers that were designed to boot only from a floppy drive. For modern computers the "no emulation" mode is generally the more reliable method. The BIOS will assign

3731-468: The company he founded, Gauss Electrophysics. The LaserDisc was the immediate precursor to the CD, with the primary difference being that the LaserDisc encoded information through an analog process whereas the CD used digital encoding. Key work to digitize the optical disc was performed by Toshi Doi and Kees Schouhamer Immink during 1979–1980, who worked on a taskforce for Sony and Philips . The result

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3822-423: 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 ". 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

3913-500: 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. A track (a group of sectors) inside a CD-ROM only contains sectors in the same mode, but if multiple tracks are present in

4004-879: The development of a working paper for such a standard. In November 1985, representatives of computer hardware manufacturers gathered at the High Sierra Hotel and Casino (currently called the Golden Nugget Lake Tahoe ) in Stateline, Nevada . This group became known as the High Sierra Group ( HSG ). Present at the meeting were representatives from Apple Computer , AT&T , Digital Equipment Corporation (DEC), Hitachi , LaserData , Microware , Microsoft , 3M , Philips , Reference Technology Inc. , Sony Corporation , TMS Inc. , VideoTools (later Meridian ), Xebec , and Yelick . The meeting report evolved from

4095-420: The directory, and the index of its parent directory path table entry. The parent directory number is a 16-bit number, limiting its range from 1 to 65,535. Directory entries are stored following the location of the root directory entry, where evaluation of filenames is begun. Both directories and files are stored as extents , which are sequential series of sectors. Files and directories are differentiated only by

4186-401: The disc at 1600 to 4000 rpm, giving a linear velocity of 9.6 m/s and a transfer rate of 1200 Kbyte/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

4277-403: The documentation for mkisofs states filenames up to 103 characters in length do not appear to cause problems. Microsoft has documented it "can use up to 110 characters." The difference lies in whether CDXA extension space is used. Joliet allows Unicode characters to be used for all text fields, which includes file names and the volume name. A "Secondary" volume descriptor with type 2 contains

4368-553: The early 2000s, and the use of CD-ROMs for commercial software is now uncommon. The earliest theoretical work on optical disc storage was done by independent researchers in the United States including David Paul Gregg (1958) and James Russel (1965–1975). In particular, Gregg's patents were used as the basis of the LaserDisc specification that was co-developed between MCA and Philips after MCA purchased Gregg's patents, as well as

4459-401: The end of the 1980s. In 1990, Data East demonstrated an arcade system board that supported CD-ROMs, similar to 1980s LaserDisc video games but with digital data, allowing more flexibility than older LaserDisc games. By early 1990, about 300,000 CD-ROM drives were sold in Japan, while 125,000 CD-ROM discs were being produced monthly in the United States. Some computers that were marketed in

4550-417: The end of the descriptor set. The primary volume descriptor provides information about the volume, characteristics and metadata, including a root directory record that indicates in which sector the root directory is located. Other fields contain metadata such as the volume's name and creator, along with the size and number of logical blocks used by the file system. Path tables summarize the directory structure of

4641-422: The file system and a volume descriptor set terminator for indicating the end of the descriptor sequence. The volume descriptor set terminator is simply a particular type of volume descriptor with the purpose of marking the end of this set of structures. The primary volume descriptor provides information about the volume, characteristics and metadata, including a root directory record that indicates in which sector

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4732-406: The file system are empty and reserved for other uses. The rest begins with a volume descriptor set (a header block which describes the subsequent layout) and then the path tables, directories and files on the disc. An ISO 9660 compliant disc must contain at least one primary volume descriptor describing the file system and a volume descriptor set terminator which is a volume descriptor that marks

4823-524: The filename restrictions inherent with full ISO 9660 compliance. Joliet accomplishes this by supplying an additional set of filenames that are encoded in UCS-2 BE ( UTF-16 BE in practice since Windows 2000). These filenames are stored in a special supplementary volume descriptor, that is safely ignored by ISO 9660-compliant software, thus preserving backward compatibility. The specification only allows filenames to be up to 64 Unicode characters in length. However,

4914-417: The first 32,768 data bytes of the disc (16 sectors of 2,048 bytes each), is unused by ISO 9660 and therefore available for other uses. While it is suggested that they are reserved for use by bootable media , a CD-ROM may contain an alternative file system descriptor in this area, and it is often used by hybrid CDs to offer classic Mac OS -specific and macOS -specific content. The data area begins with

5005-470: The first Japanese COMDEX computer show in 1985. In November 1985, several computer industry participants, including Microsoft , Philips , Sony , Apple and Digital Equipment Corporation, met to create a specification to define a file system format for CD-ROMs. The resulting specification, called the High Sierra format, was published in May 1986. It was eventually standardized, with a few changes, as

5096-419: The following structure: The data field of a volume descriptor may be subdivided into several fields, with the exact content depending on the type. Redundant copies of each volume descriptor can also be included in case the first copy of the descriptor becomes corrupt. Standard volume descriptor types are the following: An ISO 9660 compliant disc must contain at least one primary volume descriptor describing

5187-524: The form of ISO 9660/Amendment 1, intended to "bring harmonization between ISO 9660 and widely used ' Joliet Specification'." In December 2017, a 3rd Edition of ECMA-119 was published that is technically identical with ISO 9660, Amendment 1. In 2019, ECMA published a 4th version of ECMA-119, integrating the Joliet text as "Annex C". In 2020, ISO published Amendment 2, which adds some minor clarifying matter, but does not add or correct any technical information of

5278-503: The format and meaning of the corresponding system use fields: Amiga Rock Ridge is similar to RRIP, except it provides additional properties used by AmigaOS . It too is built on the SUSP standard by defining an "AS"-tagged system use field. Thus both Amiga Rock Ridge and the POSIX RRIP may be used simultaneously on the same volume. Some of the specific properties supported by this extension are

5369-717: The full standard. All numbers in ISO 9660 file systems except the single byte value used for the GMT offset are unsigned numbers. As the length of a file's extent on disc is stored in a 32 bit value, it allows for a maximum length of just over 4.2  GB (more precisely, one byte less than 4  GiB ). It is possible to circumvent this limitation by using the multi-extent (fragmentation) feature of ISO 9660 Level 3 to create ISO 9660 file systems and single files up to 8 TB. With this, files larger than 4 GiB can be split up into multiple extents (sequential series of sectors), each not exceeding

5460-538: 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 , created in 1983, defines the specifications for CD-ROMs, standardized in 1988 as the ISO / IEC 10149 standard and in 1989 as the ECMA -130 standard. The CD-ROM standard builds on top of

5551-490: The issue of the initial edition of the ECMA-119 standard in December 1986. The ECMA submitted their standard to the International Standards Organization (ISO) for fast tracking , where it was further refined into the ISO 9660 standard. For compatibility the second edition of ECMA-119 was revised to be equivalent to ISO 9660 in December 1987. ISO 9660:1988 was published in 1988. The main changes from

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5642-673: 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

5733-399: The next few years the company expanded from its academic base into medical, business and health and safety CD publishing. In 1989 the firm launched MultiPlatter, a system for networking CD-ROMs across local area networks . In 1991, it introduced searching the data held at the company's site by ERL (the electronic reference library), a system for providing hard disk access to its databases via

5824-412: The optical head moves to different positions, the angular velocity is varied from about 500 rpm at the inner edge to 200 rpm at the outer edge. The 1× speed rating for CD-ROM (150 Kbyte/s) is different from the 1× speed rating for DVDs (1.32 MB/s). When the speed at which the disc is spun is increased, data can be transferred at greater rates. For example, a CD-ROM drive that can read at 8× speed spins

5915-473: 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 or ECMA. There are several standards that define how to structure data files on a CD-ROM. ISO 9660 defines

6006-432: 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

6097-576: 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

6188-463: The outward data track is extended to the disc's outer rim. A standard 120 mm, 700 MB CD-ROM can actually hold about 703 MB of data with error correction (or 847 MB total). In comparison, a single-layer DVD-ROM can hold 4.7 GB (4.7 × 10 bytes) of error-protected data, more than 6 CD-ROMs. 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

6279-448: The path table provided by the file system. This path table stores information about each directory, its parent, and its location on disc. Since the path table is stored in a contiguous region, it can be searched much faster than jumping to the particular locations of each directory in the file's path, thus reducing seek time. The standard specifies three nested levels of interchange (paraphrased from section 10): Additional restrictions in

6370-529: 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. Above 12× speed, there are problems with vibration and heat. CAV drives give speeds up to 30× at

6461-419: The primary volume descriptor is guaranteed to be a small subset of ASCII. Apple Computer authored a set of extensions that add ProDOS or HFS / HFS+ (the primary contemporary file systems for the classic Mac OS ) properties to the filesystem. Some of the additional metadata properties include: In order to allow non-Macintosh systems to access Macintosh files on CD-ROMs, Apple chose to use an extension of

6552-402: The primary volume descriptor(s), supplementary volume descriptors or enhanced volume descriptors may be present. Path tables summarize the directory structure of the relevant directory hierarchy. For each directory in the image, the path table provides the directory identifier, the location of the extent in which the directory is recorded, the length of any extended attributes associated with

6643-574: The relevant directory hierarchy. For each directory in the image, the path table provides the directory identifier, the location of the extent in which the directory is recorded, the length of any extended attributes associated with the directory, and the index of its parent directory path table entry. There are several extensions to ISO 9660 that relax some of its limitations. Notable examples include Rock Ridge (Unix-style permissions and longer names), Joliet ( Unicode , allowing non- Latin scripts to be used), El Torito (enables CDs to be bootable ) and

6734-410: The root directory is located. Other fields contain the description or name of the volume, and information about who created it and with which application. The size of the logical blocks which the file system uses to segment the volume is also stored in a field inside the primary volume descriptor, as well as the amount of space occupied by the volume (measured in number of logical blocks). In addition to

6825-510: The same information as the Primary one (sector 16 offset 40 bytes), but in UCS-2BE in sector 17, offset 40 bytes. As a result of this, the volume name is limited to 16 characters. Many current PC operating systems are able to read Joliet-formatted media, thus allowing exchange of files between those operating systems even if non-Roman characters are involved (such as Arabic, Japanese or Cyrillic), which

6916-575: 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, GigaRec and double-density compact disc ( Purple Book standard) recorders, their utility

7007-482: 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, and a subset of it evolved into the UDF format, which was adopted for DVDs . A bootable CD specification, called El Torito ,

7098-557: The standard ISO 9660 format. Most of the data, other than the Apple specific metadata, remains visible to operating systems that are able to read ISO 9660. For operating systems which do not support any extensions, a name translation file TRANS.TBL must be used. The TRANS.TBL file is a plain ASCII text file. Each line contains three fields, separated by an arbitrary amount of whitespace : Most implementations that create TRANS.TBL files put

7189-451: The standard. The following is the rough overall structure of the ISO 9660 file system. Multi-byte values can be stored in three different formats: little-endian , big-endian , and in a concatenation of both types in what the specification calls "both-byte" order. Both-byte order is required in several fields in the volume descriptors and directory records, while path tables can be either little-endian or big-endian. The system area ,

7280-462: The structure of sectors in CD-ROM XA modes: 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

7371-479: The system use area. SUSP defines several common tags and system use fields: Other known SUSP fields include: The Apple extensions do not technically follow the SUSP standard; however the basic structure of the AA and AB fields defined by Apple are forward compatible with SUSP; so that, with care, a volume can use both Apple extensions as well as RRIP extensions. The Rock Ridge Interchange Protocol (RRIP, IEEE P1282)

7462-408: The system. SUSP defines a method to subdivide that area into multiple system use fields, each identified by a two-character signature tag. The idea behind SUSP was that it would enable any number of independent extensions to ISO 9660 to be created and included on a volume without conflicting. It also allows for the inclusion of property data that would otherwise be too large to fit within the limits of

7553-407: 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 sub code). Unlike audio CDs,

7644-466: Was IBM 's ThinkPad 755CD in 1994. On early audio CD players that were released prior to the advent of the CD-ROM, the raw binary data of CD-ROM was played back as noise. To address this problem, the subcode channel Q has a "data" flag in areas of the disc that contain computer data rather than playable audio. The data flag instructs CD players to mute the audio. CD-ROMs are identical in appearance to audio CDs , and data are stored and retrieved in

7735-753: Was defined in the Yellow Book specification in 1983. However, this book did not define any format for organizing data on CD-ROMs into logical units such as files , which led to every CD-ROM maker creating its own format. In order to develop a CD-ROM file system standard ( Z39.60 - Volume and File Structure of CDROM for Information Interchange ), the National Information Standards Organization (NISO) set up Standards Committee SC EE (Compact Disc Data Format) in July 1985. In September/ October 1985 several companies invited experts to participate in

7826-416: Was formerly not possible with plain ISO 9660-formatted media. Operating systems which can read Joliet media include: Romeo was developed by Adaptec and allows the use of long filenames up to 128 characters, written directly into the primary volume descriptor using the current code page . This format is built around the workings of Windows 9x and Windows NT "CDFS" drivers. When a Windows installation of

7917-572: Was intended as a bridge between CD-ROM and CD-i ( Green Book ) and was published by Sony and Philips , and backed by Microsoft , in 1991, first announced in September 1988. "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

8008-413: Was issued in January 1995, to make a CD emulate a hard disk or floppy disk . 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

8099-1082: Was nullified by the introduction of consumer DVD-ROM drives capable of consistent 36× equivalent CD-ROM speeds (4× DVD) or higher. Additionally, with a 700 MB CD-ROM fully readable in under 2.5 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 GB (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.

8190-472: Was started in 1986 from a small building in Newton Lower Falls, Massachusetts. The company began experimenting with four databases: ERIC , LISA , PsycLIT , and EMBASE . In 1987 the company had 12 databases and revenues of approximately $ 6m. Competing with CD Plus (now Ovid Technologies ), Aries, Cambridge Scientific Abstracts and Dialog , the company offered libraries a wide range of CD-ROMs. Over

8281-510: Was the Compact Disc Digital Audio (CD-DA), defined in 1980. The CD-ROM was later designed as an extension of the CD-DA, and adapted this format to hold any form of digital data, with an initial storage capacity of 553 MB . Sony and Philips created the technical standard that defines the format of a CD-ROM in 1983, in what came to be called the Yellow Book . The CD-ROM was announced in 1984 and introduced by Denon and Sony at

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