Compact Disc logo/trademark

CD-ROM (an abbreviation of "Compact Disc read-only memory") is a Compact Disc that contains data accessible by a computer. Optical disc authoring, including DVD and Blu-ray Disc authoring (often referred to colloquially but improperly as burning) is the process of assembling In Computing, an optical disc drive ( ODD) is a Disk drive that uses Laser light or electromagnetic waves near the Light spectrum Optical disc authoring, including DVD and Blu-ray Disc authoring (often referred to colloquially but improperly as burning) is the process of assembling Optical disc authoring software is Computer software for authoring optical discs including CD-ROMs and DVDs They are also known by synonyms Optical disc authoring requires a number of different technologies working in tandem from the media to the firmware to the control electronics of the drive. In Optical disc authoring, there are multiple modes for recording including Disc-At-Once, Track-At-Once, and Session-At-Once. Packet writing is an Optical disc recording technology used to allow write-once and rewritable CD and DVD media to be used in a similar manner to a The Laserdisc (LD is an obsolete Home video disc format and was the first commercial Optical disc storage medium Video Single Disc (abbreviated as VSD was a disc-based format that carried the same analog video information as a Laserdisc, but on a 12-centimetre (4 A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) The DTS-CD, DTS Audio CD or 51 Music Disc (official name is an audio Compact Disc that contains music in Surround sound format Super Audio CD ( SACD) is a read-only optical audio disc format that can provide higher fidelity digital audio reproduction than the Red Photo CD is a system designed by Kodak for digitizing and storing photos in a CD A CD-R ( C ompact D isc- R ecordable is a variation of the Compact Disc invented by Philips and Sony. Compact Disc ReWritable (CD-RW is a rewritable Optical disc format This article is about 'CD Video' a hybrid analog/digital format Super Video CD ( Super Video Compact Disc or SVCD) is a Digital format for storing Video on standard Compact discs SVCD was intended A CD+G (also known as CD+Graphics) is a special audio Compact disc that contains Graphics Data in addition to the audio data CD-Text is an extension of the Red Book Compact Disc specifications standard for Audio CDs It allows for storage of additional information (e CD-ROM XA is an extension of the Yellow Book Mode 2 standard for CD-ROMs that combines compressed audio visual and computer data allowing all to be accessed CD-i or Compact Disc Interactive is the name of an interactive multimedia CD player developed and marketed by Royal Philips Electronics N A MiniDisc ( MD) is a Magneto-optical disc-based Data storage device initially intended for storage of up to 80 minutes of digitized audio In January 2004 Sony announced the Hi-MD media storage format as a further development of the MiniDisc-Format. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is DVD-R is a DVD recordable format A DVD-R typically has a storage capacity of 4 A DVD+R is a once-writable Optical disc with 47 GB (4377 GiB) of storage capacity (more precisely 2295104 sectors of 2048 Bytes DVD-R DL (DL stands for Dual Layer) also called DVD-R9, is a derivative of the DVD-R format standard DVD+R DL (DL stands for Double Layer) also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. A DVD-RW disc is a rewritable Optical disc with equal storage capacity to a DVD-R, typically 4 DVD+RW is the name of a standard for Optical discs one of several types of DVD, which hold up to about 4 DVD-RW DL is a rewritable Optical disc standard with storage capacity of 8 A DVD+RW DL is a rewritable Optical disc with storage capacity of 8 DVD-RAM ( DVD – Random Access Memory) is a disc specification presented in 1996 by the DVD Forum, which specifies rewritable DVD-RAM media and the appropriate DVD-Ds, also referred to as disposable DVDs are a type of digital video disc that is designed to be used for a maximum 48 hours after the containing package is opened Ultra Density Optical ( UDO) is an Optical disc format designed for high-density storage of high-definition video and The Universal Media Disc ( UMD) is an Optical disc medium developed by Sony for use on the PlayStation Portable. not insert the publicly disclosed HD DVD key into this article for the time being not insert the publicly disclosed HD DVD key into this article for the time being not insert the publicly disclosed HD DVD key into this article for the time being not insert the publicly disclosed HD DVD key into this article for the time being not insert the publicly disclosed HD DVD key into this article for the time being Blu-ray Disc recordable (or BD-R) refers to two Optical disc formats that can be recorded with an Optical disc recorder. For the series of US government publications on Computer security standards see Rainbow Series. ISO 9660 a standard published by the International Organization for Standardization (ISO defines a File system for CD-ROM media Joliet is the name of an extension to the ISO 9660 File system. The Rock Ridge Interchange Protocol (RRIP IEEE P1282 is an extension to the ISO 9660 volume format which adds POSIX File system semantics The El Torito Bootable CD Specification is an extension to the ISO 9660 CD-ROM specification The primary file system for Apple Macintosh computers is HFS (or HFS+ Mount Rainier ( MRW) is a format for writable Optical discs which provides the Packet writing and defect management Although research into Optical data storage has been ongoing for many decades the first popular system was the Compact Disc, introduced in 1982, adapted to data A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio While the Compact Disc format was originally designed for music storage and playback, the format was later adapted to hold any form of binary data. CD-ROMs are popularly used to distribute computer software, including games and multimedia applications, though any data can be stored (up to the capacity limit of a disc). Multimedia is media and content that utilizes a combination of different content forms. Some CDs hold both computer data and audio with the latter capable of being played on a CD player, whilst data (such as software or digital video) is only usable on a computer (such as PC CD-ROMs). CD-ROM (an initialism of "Compact Disc Read-Only Memory " is a pre-pressed Compact Disc that contains data accessible to but not writable These are called Enhanced CDs. Enhanced CD, also known as CD Extra and CD Plus, is a Certification mark of the Recording Industry Association of America for various technologies

Although many people use lowercase letters in this acronym, proper presentation is in all capital letters with a hyphen between CD and ROM. It was also suggested by some, especially soon after the technology was first released, that CD-ROM was an acronym for "Compact Disc read-only-media", or that it was a more 'correct' definition. This was not the intention of the original team who developed the CD-ROM, and common acceptance of the 'memory' definition is now almost universal. This is probably in no small part due to the widespread use of other 'ROM' acronyms such as Flash-ROMs and EEPROMs where 'memory' is usually the correct term.

Media

Main article: Compact Disc

CD-ROM discs are identical in appearance to audio CDs, and data is stored and retrieved in a very similar manner (only differing from audio CDs in the standards used to store the data). A Compact Disc (also known as a CD) is an Optical disc used to store digital data, originally developed for storing digital audio Discs are made from a 1. 2 mm thick disc of polycarbonate plastic, with a thin layer of aluminium to make a reflective surface. Plastic is the general common term for a wide range of synthetic or semisynthetic organic solid materials suitable for the manufacture of industrial products WikipediaNaming The most common size of CD-ROM disc is 120 mm in diameter, though the smaller Mini CD standard with an 80 mm diameter, as well as numerous non-standard sizes and shapes (e. Not to be confused with MiniDisc. Mini CD s or "Pocket" CDs are Compact discs with a smaller Form factor g. business card-sized media) are also available. Data is stored on the disc as a series of microscopic indentations ("pits", with the gaps between them referred to as "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 the incoming beam, causing destructive interference and reducing the reflected beam's intensity. The phase of an oscillation or wave is the fraction of a complete cycle corresponding to an offset in the displacement from a specified reference point at time t = 0 In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern This pattern of changing intensity of the reflected beam is converted into binary data.

Standards

There are several formats used for data stored on compact discs, known collectively as the Rainbow Books. For the series of US government publications on Computer security standards see Rainbow Series. These include the original Red Book standards for CD audio, White Book and Yellow Book CD-ROM. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) The White Book, which was released in 1987 by Sony, Philips, Matsushita, and JVC refers to a standard of Compact disc that The Yellow Book is the Standard that defines the format of CD-ROMs The Yellow Book created by Sony and Philips, was the first extension of the The ECMA-130 standard, which gives a thorough description of the physics and physical layer of the CD-ROM, inclusive of Cross-interleaved Reed-Solomon coding CIRC and Eight-to-Fourteen Modulation, can be downloaded from [1]. In the Compact disc system Error correction and detection is provided by cross-interleaved Reed-Solomon code. Eight-to-Fourteen Modulation ( EFM) is a data encoding technique used by CDs and pre- Hi-MD MiniDiscs EFM and EFMPlus were both invented

ISO 9660 defines the standard file system of a CD-ROM, although it is due to be replaced by ISO 13490. ISO 9660 a standard published by the International Organization for Standardization (ISO defines a File system for CD-ROM media ISO/IEC 13490 (also known as ECMA -168) is the next version of ISO 9660 (level 3 intended to describe the File system of a CD-ROM UDF format is used on user-writeable CD-R and CD-RW discs that are intended to be extended or overwritten. The Universal Disk Format ( UDF) is a format specification of a File system for storing files on optical media A CD-R ( C ompact D isc- R ecordable is a variation of the Compact Disc invented by Philips and Sony. Compact Disc ReWritable (CD-RW is a rewritable Optical disc format The bootable CD specification, to make a CD emulate a hard disk or floppy, is called El Torito. Apparently named this because its design originated in an El Torito restaurant in Irvine, California. The El Torito Bootable CD Specification is an extension to the ISO 9660 CD-ROM specification malith.

CD-ROM format

A CD-ROM sector contains 2352 bytes, divided into 98 24-byte frames. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. The CD-ROM is, in essence, a data disk, which cannot rely on error concealment, and therefore requires a higher reliability of the retrieved data. In order to achieve improved error correction and detection, a CD-ROM has a third layer of Reed-Solomon error correction. Reed-Solomon error correction is an Error-correcting code that works by Oversampling a Polynomial constructed from the data ^[1] A Mode-1 CD-ROM, which has the full three layers of error correction data, contains a net 2048 bytes of the available 2352 per sector. In a Mode-2 CD-ROM, which is mostly used for video files, there are 2336 user-available bytes per sector. The net byte rate of a Mode-1 CD-ROM, based on comparison to CDDA audio standards, is 44. 1k/s×4B×2048/2352 = 153. 6 kB/s. The playing time is 74 minutes, or 4440 seconds, so that the net capacity of a Mode-1 CD-ROM is 682 MB.

A 1x speed CD drive reads 75 consecutive sectors per second.

CD sector contents

• A standard 74 min CD contains 333,000 blocks or sectors. In the context of Computer Disk storage, a sector is a subdivision of a track (Figure 1 item A on a Magnetic disk or Optical disc
• Each sector is 2352 bytes, and contains 2048 bytes of PC (MODE1) Data, 2336 bytes of PSX/VCD (MODE2) Data, or 2352 bytes of AUDIO.
• The difference between sector size and data content are the Headers info and the Error Correction Codes, that are big for Data (high precision required), small for VCD (standard for video) and none for audio.
• If extracting the disc in RAW format (standard for creating images) always extract 2352 bytes per sector, not 2048/2336/2352 bytes depending on data type (basically, extracting the whole sector). This fact has two main consequences:
  • Recording data CDs at very high speed (40x) can be done without losing information. However, as audio CDs do not contain a third layer of error correction codes, recording these at high speed may result in more unrecoverable errors or 'clicks' in the audio. In Mathematics, Computer science, Telecommunication, and Information theory, error detection and correction has great practical importance in
  • On a 74 minute CD, one can fit larger images using RAW mode, up to 333,000 × 2352 = 783,216,000 bytes (747~ MiB). A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. This is the upper limit for RAW images created on a 74 min or 650~ MiB Red Book CD. A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) The 14. 8% increase is due to the discarding of error correction data
• Please note that an image size is always a multiple of 2352 bytes (the size of a block) when extracting in RAW mode. ^[2]

Manufacture

Main article: CD manufacturing

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 in turn are used to manufacture multiple copies of the final disc with the pits already present. Compact disc manufacturing is the process by which commercial Compact discs (CDs are replicated in mass quantities using a master version created from a source recording Recordable (CD-R) and rewritable (CD-RW) discs are manufactured by a similar method, but the data is recorded on them by a laser changing the properties of a dye or phase change material in a process that is often referred to as "burning". A CD-R ( C ompact D isc- R ecordable is a variation of the Compact Disc invented by Philips and Sony. Compact Disc ReWritable (CD-RW is a rewritable Optical disc format In Thermodynamics, phase transition or phase change is the transformation of a thermodynamic system from one phase to another Optical disc authoring, including DVD and Blu-ray Disc authoring (often referred to colloquially but improperly as burning) is the process of assembling

Capacity

The CD-ROM can easily contain all the encyclopaedia's words and images, plus audio & video clips

A standard 120 mm CD-ROM holds up to 737 MiB (783 million bytes) of data. A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. To put this storage capacity into context, the average novel contains 100,000 words. A novel (from Italian novella, Spanish novela, French nouvelle for "new" "news" or "short story Assume that average word length is 10 letters and that each letter occupies one byte. A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. A novel therefore might occupy 1,000,000 bytes (1000 kB, without layout information). One CD can therefore contain around 700 novels. If each novel occupies at least one centimetre of bookshelf space, then one CD can contain the equivalent of seven metres of bookshelf. However, textual data can be compressed by more than a factor of ten, using compression algorithms, so a CD-ROM can accommodate close to 100 metres of bookshelf space.

In comparison a single layer DVD contains 4. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is 4 GiB of data, approximately 6 times the amount of a CD-ROM.

CD capacities are always given in binary units, although decimal SI prefixes are usually used: a "700 MB" CD has a nominal capacity of about 700 MiB. An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol to form a Decimal multiple or A mebibyte (a contraction of me ga bi nary byte) is a unit of Information or Computer storage, abbreviated MiB. DVD capacities, on the other hand, are given in decimal units: a "4. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is 7 GB" DVD has a nominal capacity of about 4. 38 GiB. A gibibyte (a contraction of gi ga bi nary byte) is a unit of Information or Computer storage, abbreviated GiB.

CD-ROM drives

Further information: Optical disc drive

Old 4x CD-ROM Drive

CD-ROM discs are read using CD-ROM drives, which are now almost universal on personal computers. In Computing, an optical disc drive ( ODD) is a Disk drive that uses Laser light or electromagnetic waves near the Light spectrum A CD-ROM drive may be connected to the computer via an IDE (ATA), SCSI, S-ATA, Firewire, or USB interface or a proprietary interface, such as the Panasonic CD interface. AT Attachment with Packet Interface ( ATA/ATAPI) is a standard interface used to connect storage devices such as Hard disks Solid-state The IEEE 1394 interface is a serial bus Interface standard for high-speed communications and Isochronous real-time data transfer frequently The Panasonic CD interface, also known as the MKE CD interface (for Matsushita Kotobuki Electronics SLCD or simply Panasonic, is a proprietary Virtually all modern CD-ROM drives can also play audio CDs as well as Video CDs and other data standards when used in conjunction with the right software. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA)

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

The rate at which CD-ROM drives can transfer data from the disc is gauged by a speed factor relative to music CDs: 1x or 1-speed which gives a data transfer rate of 150 kilobytes per second in the most common data format. 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 8x speed spins the disc at up to 4000 rpm (compared to the 500 rpm maximum for 1x speed), giving a transfer rate of 1. 2 megabytes per second. In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission Above 12x speed, vibration and heat can become a problem. CD-ROM drives above this speed tackle the problem in several ways. Constant angular velocity (CAV) drives spin the disc at a constant rate, leading to faster data transfer when reading from the outer parts of the disc, but slower towards the centre. In Optical storage, constant angular velocity (CAV is a qualifier for the rated speed of an Optical disc drive, and may also be applied to the writing speed of recordable 20x 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. The Samsung Group ( Korean:, Samsung Guerup) is South Korea 's largest company or Chaebol and the world's largest conglomerate A bearing is a device to permit constrained relative motion between two parts typically rotation or linear movement As of 2004, the fastest transfer rate commonly available is about 52x or 10,350 rpm and 7. 62 megabytes per second, though this is only when reading information from the outer parts of a disc. Future speed increases based simply upon spinning the disc faster are particularly limited by the strength of polycarbonate plastic used in CD manufacturing, though improvements can still be obtained by the use of multiple laser pickups as demonstrated by the Kenwood TrueX 72x which uses seven laser beams and a rotation speed of approximately 10x.

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; ie a 12x/10x/32x CD drive can, CPU and media permitting, write to CD-R discs at 12x speed (1. 76 MB/s), write to CD-RW discs at 10x speed (1. A megabyte is a unit of Information or Computer storage equal to either 106 (1000000 Bytes or 220 (1048576 bytes depending on 46 MB/s), and read from CD discs at 32x speed (4. 69 MB/s).

The 1x speed rating for CDs (150 kB/s) is not to be confused with the 1x speed rating for DVDs (1. DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is 32 MB/s).

A view of a CD-ROM drive's disassembled laser system.

The movement of the laser enables reading at any position of the CD.

The laser system of a CD Drive.

Common transfer speeds:

Copyright issues

Main article: CD/DVD copy protection

There has been a move by the recording industry to make audio CDs (CDDAs, Red Book CDs) unplayable on computer CD-ROM drives, to prevent the copying of music. CD/DVD copy protection is a blanket term for various methods of Copy protection for CDs and DVDs Such methods include DRM, CD-checks Dummy The record industry is the part of the Music industry that sells Sound recordings of Music. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) This is done by intentionally introducing errors onto the disc that the embedded circuits on most stand-alone audio players can automatically compensate for, but which may confuse CD-ROM drives. Consumer rights advocates are as of October 2001 pushing to require warning labels on compact discs that do not conform to the official Compact Disc Digital Audio standard (often called the Red Book) to inform consumers of which discs do not permit full fair use of their content. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) Fair use is a doctrine in United States copyright law that allows limited use of copyrighted material without requiring permission from the rights holders such as use for

In 2005, Sony BMG Music Entertainment was criticised when a copy protection mechanism known as Extended Copy Protection (XCP) used on some of their audio CDs automatically and surreptitiously installed copy-prevention software on computers (see 2005 Sony BMG CD copy protection scandal). Sony BMG Music Entertainment is a diverse music and entertainment group XCP redirects here For other uses see XCP (disambiguation. Extended Copy Protection (XCP is a software package The Sony BMG CD copy prevention scandal concerns the Copy prevention measures included by Sony BMG on Compact discs in 2005 Such discs are not legally allowed to be called CDs or Compact Discs because they break the Red Book standard governing CDs, and Amazon. com for example describes them as "copy protected discs" rather than "compact discs" or "CDs".

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. A CD-R ( C ompact D isc- R ecordable is a variation of the Compact Disc invented by Philips and Sony. Compact Disc ReWritable (CD-RW is a rewritable Optical disc format ^[3] This is a counterpart to the SID — the Source Identification Code, an eight character code beginning with "IFPI" that is usually stamped on discs produced by CD recording plants. The International Federation of the Phonographic Industry ( IFPI) is the organization that represents the interests of the Recording industry worldwide

See also

• Red Book (audio CD standard)
• DVD-Audio
• Computer hardware
• Phase-change Dual
• DVD-ROM
• CD/DVD authoring
• CD shattering
• MultiLevel Recording, an obsolete technology (with non-binary modulation)

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. Red Book is the standard for audio CDs ( Compact Disc Digital Audio system or CDDA) DVD-Audio (commonly abbreviated as DVD-A) is a digital format for delivering very High-fidelity audio content on a DVD. Typical PC hardware A typical Personal computer consists of a case or chassis in a tower shape (desktop and the following parts Motherboard Phase-Change Dual (PD is a rewritable Optical disc format introduced by Panasonic in 1995 DVD (also known as " Digital Versatile Disc " or " Digital Video Disc " - see Etymology)is Optical disc authoring, including DVD and Blu-ray Disc authoring (often referred to colloquially but improperly as burning) is the process of assembling CD shattering, a phenomenon also known as exploding CDs, occurs when a CD shatters inside a high speed CD-ROM drive (48X or higher with a loud cracking MultiLevel Recording ( ML) was a technology developed by Calimetrics to increase the storage capacity of Optical discs. The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software

Further reading

• Stability Comparison of Recordable Optical Discs - A study of error rates in harsh conditions.
• Care, Handling and Storage of Removeable Media.

External links

• How CDs Work from HowStuffWorks.com
• Andy McFadden's CD-Recordable FAQ
• Understanding CD-R & CD-RW by Hugh Bennett
• Inside a CD-ROM drive from The PC Doctor
• Comparative perspective on CD data transfer rates. Database for examination.