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128-417: 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 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

256-828: 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 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

384-509: A vulnerability . Software patches are often released to fix identified vulnerabilities, but those that remain unknown ( zero days ) as well as those that have not been patched are still liable for exploitation. Vulnerabilities vary in their ability to be exploited by malicious actors, and the actual risk is dependent on the nature of the vulnerability as well as the value of the surrounding system. Although some vulnerabilities can only be used for denial of service attacks that compromise

512-520: A web application —had become the primary method that companies deliver applications. Software companies aim to deliver a high-quality product on time and under budget. A challenge is that software development effort estimation is often inaccurate. Software development begins by conceiving the project, evaluating its feasibility, analyzing the business requirements, and making a software design . Most software projects speed up their development by reusing or incorporating existing software, either in

640-450: A 1. A Red Book -compatible CD-R has pit-and-land-shaped spots on a layer of organic dye instead of actual pits and lands; a laser creates the spots by altering the reflective properties of the dye. Due to the weaker error correction sector structure used on audio CDs and video CDs ( Mode 2 Form 2 ) than on data discs ( Mode 1 or Mode 2 Form 1 ), C2 errors are not correctable and signify data loss. Even with uncorrectable errors,

768-452: 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

896-474: A 150-minute playing time, 44,056 Hz sampling rate, 16-bit linear resolution, and cross-interleaved Reed-Solomon coding (CIRC) error correction code —specifications similar to those later settled upon for the standard compact disc format in 1980. Technical details of Sony's digital audio disc were presented during the 62nd AES Convention, held on 13–16 March 1979, in Brussels . Sony's AES technical paper

1024-433: A CD is called a track . A CD can contain up to 99 tracks (including a data track for mixed mode discs ). Each track can in turn have up to 100 indexes, though players which still support this feature have become rarer over time. The vast majority of songs are recorded under index 1, with the pregap being index 0. Sometimes hidden tracks are placed at the end of the last track of the disc, often using index 2 or 3, or using

1152-466: A CD-DA consists of two-channel signed 16- bit LPCM sampled at 44,100 Hz and written as a little-endian interleaved stream with left channel coming first. The sampling rate is adapted from that attained when recording digital audio on videotape with a PCM adaptor , an earlier way of storing digital audio. An audio CD can represent frequencies up to 22.05 kHz, the Nyquist frequency of

1280-416: 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 ;

1408-467: A binary flag in the disc subcode instructs the player to apply de-emphasis filtering if appropriate. Playback of such discs in a computer or ripping to WAV files typically does not take into account the pre-emphasis, so such files play back with an incorrect frequency response. FFmpeg has a filter to remove (or apply) the pre-emphasis in order to create standard WAV files, or to create CDs with pre-emphasis. Four-channel, or quadraphonic , supported

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1536-464: A block of 588 pairs of left and right audio samples. Timecode contained in the subchannel data allows the reading device to locate the region of the disc that corresponds to the timecode in the TOC. The TOC on discs is analogous to the partition table on hard drives . Nonstandard or corrupted TOC records are abused as a form of CD/DVD copy protection , in e.g. the key2Audio scheme. The largest entity on

1664-413: 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

1792-457: A change request. Frequently, software is released in an incomplete state when the development team runs out of time or funding. Despite testing and quality assurance , virtually all software contains bugs where the system does not work as intended. Post-release software maintenance is necessary to remediate these bugs when they are found and keep the software working as the environment changes over time. New features are often added after

1920-486: A code's correct and efficient behavior, its reusability and portability , or the ease of modification. It is usually more cost-effective to build quality into the product from the beginning rather than try to add it later in the development process. Higher quality code will reduce lifetime cost to both suppliers and customers as it is more reliable and easier to maintain . Software failures in safety-critical systems can be very serious including death. By some estimates,

2048-499: A compact disc player uses error concealment with the aim of making the damage unhearable. The audio data stream in an audio CD is continuous but has three parts. The main portion, further divided into playable audio tracks, is the program area . This section is preceded by a lead-in track and followed by a lead-out track. The lead-in and lead-out tracks encode only silent audio, but all three sections contain subcode data streams. The lead-in's subcode contains repeated copies of

2176-412: A diameter of 115 mm. Sony did not yet have such a facility. If Sony had agreed on the 115-mm disc, Philips would have had a significant competitive edge in the market. The long playing time of Beethoven's Ninth Symphony imposed by Ohga was used to push Philips to accept 120 mm, so that Philips' PolyGram lost its edge on disc fabrication. The 74-minute playing time of a CD, which is longer than

2304-427: A diameter of 20 cm (7.9 in) and a sound quality superior to that of the vinyl record. However, due to the unsatisfactory performance of the analog format, two Philips research engineers recommended a digital format in March 1974. In 1977, Philips then established a laboratory with the mission of creating a digital audio disc. The diameter of Philips's prototype compact disc was set at 11.5 cm (4.5 in),

2432-400: A former member of the task force, gives background information on the many technical decisions made, including the choice of the sampling frequency, playing time, and disc diameter. The task force consisted of around 6 persons, though according to Philips, the compact disc was "invented collectively by a large group of people working as a team". Early milestones in the launch and adoption of

2560-465: 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

2688-662: A joint task force of engineers to design a new digital audio disc. After a year of experimentation and discussion, the Red Book CD-DA standard was published in 1980. After their commercial release in 1982, compact discs and their players were extremely popular. Despite costing up to $ 1,000, over 400,000 CD players were sold in the United States between 1983 and 1984. By 1988, CD sales in the United States surpassed those of vinyl LPs, and, by 1992, CD sales surpassed those of prerecorded music-cassette tapes. The success of

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2816-563: A joint task force of engineers to design a new digital audio disc. Led by engineers Kees Schouhamer Immink and Toshitada Doi , the research pushed forward laser and optical disc technology. After a year of experimentation and discussion, the task force produced the Red Book CD-DA standard. First published in 1980, the standard was formally adopted by the IEC as an international standard in 1987, with various amendments becoming part of

2944-443: A legal regime where liability for software products is significantly curtailed compared to other products. Source code is protected by copyright law that vests the owner with the exclusive right to copy the code. The underlying ideas or algorithms are not protected by copyright law, but are often treated as a trade secret and concealed by such methods as non-disclosure agreements . Software copyright has been recognized since

3072-483: 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

3200-403: A quick web search . Most creative professionals have switched to software-based tools such as computer-aided design , 3D modeling , digital image editing , and computer animation . Almost every complex device is controlled by software. Compact Disc Digital Audio Compact Disc Digital Audio ( CDDA or CD-DA ), also known as Digital Audio Compact Disc or simply as Audio CD ,

3328-488: A second of audio: 588 pairs of left and right samples. This timecode frame is distinct from the 33-byte channel-data frame described above, and is used for time display and positioning the reading laser. When editing and extracting CD audio, this timecode frame is the smallest addressable time interval for an audio CD; thus, track boundaries only occur on these frame boundaries. Each of these structures contains 98 channel-data frames, totaling 98 × 24 = 2,352 bytes of music. The CD

3456-495: A significant role in the distribution of software products. The first use of the word software is credited to mathematician John Wilder Tukey in 1958. The first programmable computers, which appeared at the end of the 1940s, were programmed in machine language . Machine language is difficult to debug and not portable across different computers. Initially, hardware resources were more expensive than human resources . As programs became complex, programmer productivity became

3584-514: A specific version of the software, downloaded, and run on hardware belonging to the purchaser. The rise of the Internet and cloud computing enabled a new model, software as a service (SaaS), in which the provider hosts the software (usually built on top of rented infrastructure or platforms ) and provides the use of the software to customers, often in exchange for a subscription fee . By 2023, SaaS products—which are usually delivered via

3712-415: A system's availability, others allow the attacker to inject and run their own code (called malware ), without the user being aware of it. To thwart cyberattacks, all software in the system must be designed to withstand and recover from external attack. Despite efforts to ensure security, a significant fraction of computers are infected with malware. Programming languages are the format in which software

3840-460: A variation of this technique called pulse-density modulation (PDM), while Matsushita (now Panasonic ) chose pulse-width modulation (PWM), advertising it as MASH, which is an acronym derived from their patented Multi-stAge noiSe-sHaping PWM topology. The CD was primarily planned as the successor to the vinyl record for playing music, rather than as a data storage medium. However, CDs have grown to encompass other applications. In 1983, following

3968-489: 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

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4096-518: A way to produce 16-bit quality using its 14-bit DAC by using four times oversampling . Some early CDs were mastered with pre-emphasis , an artificial boost of high audio frequencies. The pre-emphasis improves the apparent signal-to-noise ratio by making better use of the channel's dynamic range. On playback, the player applies a de-emphasis filter to restore the frequency response curve to an overall flat one. Pre-emphasis time constants are 50 μs and 15 μs (9.49 dB boost at 20 kHz), and

4224-468: 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

4352-453: Is added to the beginning of each frame to assist with synchronization, so the reading device can locate frames easily. With this, a frame ends up containing 588 bits of channel data which are decoded to 192 bits of digital audio. The frames of channel data are finally written to disc physically in the form of pits and lands , with each pit or land representing a series of zeroes, and with the transition points—the edge of each pit—representing

4480-582: 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

4608-411: Is divided into frames, containing twelve samples each (six left and six right samples, alternating), for a total of 192 bits (24 bytes) of audio data per frame. This stream of audio frames is then subjected to CIRC encoding, which segments and rearranges the data and expands it with error correction codes in a way that allows occasional read errors to be detected and corrected. CIRC encoding interleaves

4736-417: 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

4864-428: 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

4992-546: 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

5120-599: 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,

5248-421: 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

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5376-499: Is the standard format for audio compact discs . The standard is defined in the Red Book technical specifications , which is why the format is also dubbed "Redbook audio" in some contexts. CDDA utilizes pulse-code modulation (PCM) and uses a 44,100 Hz sampling frequency and 16-bit resolution, and was originally specified to store up to 74 minutes of stereo audio per disc. The first commercially available audio CD player ,

5504-400: 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

5632-408: Is usually stamped on discs produced by CD recording plants. Software Software consists of computer programs that instruct the execution of a computer . Software also includes design documents and specifications. The history of software is closely tied to the development of digital computers in the mid-20th century. Early programs were written in the machine language specific to

5760-453: Is written. Since the 1950s, thousands of different programming languages have been invented; some have been in use for decades, while others have fallen into disuse. Some definitions classify machine code —the exact instructions directly implemented by the hardware—and assembly language —a more human-readable alternative to machine code whose statements can be translated one-to-one into machine code—as programming languages. Programs written in

5888-570: The 44.1 kHz sample rate. There was a long debate over the use of 16-bit (Sony) or 14-bit (Philips) quantization , and 44,056 or 44,100 samples/s (Sony) or approximately 44,000 samples/s (Philips). When the Sony/Philips task force designed the Compact Disc, Philips had already developed a 14-bit D/A converter (DAC), but Sony insisted on 16-bit. In the end Sony won, so 16 bits and 44.1 kilosamples per second prevailed. Philips found

6016-579: The PC Engine CD-ROM (TurboGrafx-CD) in 1988, while CD-ROM drives had also become available for home computers by 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

6144-566: The Sony CDP-101 , was released in October 1982 in Japan. The format gained worldwide acceptance in 1983–84, selling more than a million CD players in its first two years, to play 22.5 million discs, before overtaking records and cassette tapes to become the dominant standard for commercial music. Peaking around year 2000, the audio CD contracted over the next decade due to rising popularity and revenue from digital downloading , and during

6272-471: The Sound Blaster 16 . The optophone , first presented in 1931, was an early device that used light for both recording and playback of sound signals on a transparent photograph . More than thirty years later, American inventor James T. Russell has been credited with inventing the first system to record digital media on a photosensitive plate. Russell's patent application was filed in 1966, and he

6400-438: The high-level programming languages used to create software share a few main characteristics: knowledge of machine code is not necessary to write them, they can be ported to other computer systems, and they are more concise and human-readable than machine code. They must be both human-readable and capable of being translated into unambiguous instructions for computer hardware. The invention of high-level programming languages

6528-423: 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 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

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6656-800: The vinyl revival . During the 2010s, the increasing popularity of solid-state media and music streaming services caused automakers to remove automotive CD players in favor of minijack auxiliary inputs, wired connections to USB devices and wireless Bluetooth connections. Automakers viewed CD players as using up valuable space and taking up weight which could be reallocated to more popular features, like large touchscreens. By 2021, only Lexus and General Motors were still including CD players as standard equipment with certain vehicles. CDs continued to be strong in some markets such as Japan where 132 million units were produced in 2019. The decline in CD sales has slowed in recent years; in 2021, CD sales increased in

6784-611: The 2000s designed as successors to the CD: the Super Audio CD (SACD) and DVD-Audio . However neither of these were adopted partly due to increased relevance of digital (virtual) music and the apparent lack of audible improvements in audio quality to most human ears. These effectively extended the CD's longevity in the music market. With the advent and popularity of Internet-based distribution of files in lossy-compressed audio formats such as MP3 , sales of CDs began to decline in

6912-502: The 2000s. For example, between 2000 and 2008, despite overall growth in music sales and one anomalous year of increase, major-label CD sales declined overall by 20%. Despite rapidly declining sales year-over-year, the pervasiveness of the technology lingered for a time, with companies placing CDs in pharmacies, supermarkets, and filling station convenience stores to target buyers less likely to be able to use Internet-based distribution. In 2012, CDs and DVDs made up only 34% of music sales in

7040-465: The 2010s by digital music streaming , but has remained as one of the primary distribution methods for the music industry . In the United States, phonograph record revenues surpassed the CD in 2020 for the first time since the 1980s, but in other major markets like Japan it remains the premier music format by a distance and in Germany it outsold other physical formats at least fourfold in 2022. In

7168-403: The 22 minutes per side typical of long-playing (LP) vinyl albums , was often used to the CD's advantage during the early years when CDs and LPs vied for commercial sales. CDs would often be released with one or more bonus tracks , enticing consumers to buy the CD for the extra material. However, attempts to combine double LPs onto one CD occasionally resulted in the opposite situation in which

7296-508: The CD originally aimed at a playing time of 60 minutes with a disc diameter of 100 mm (Sony) or 115 mm (Philips). Sony vice-president Norio Ohga suggested extending the capacity to 74 minutes to accommodate the recording of Wilhelm Furtwängler conducting Ludwig van Beethoven 's Ninth Symphony at the 1951 Bayreuth Festival . The additional 14-minute playing time required increasing disc diameter. Kees Schouhamer Immink , Philips' chief engineer, however, denies this, claiming that

7424-663: The CD would instead offer less audio than the LP. One such example was with DJ Jazzy Jeff & The Fresh Prince 's double album He's the DJ, I'm the Rapper , in which initial CD releases of the album had multiple tracks edited down for length to fit on a single disc; recent CD reissues package the album across two discs as a result. The emergence of 80-minute CDs allowed for some double albums that were previously edited for length, e.g. 1999 by Prince , or packaged as double CDs, e.g. Tommy by

7552-467: The CD's introduction, Immink and Joseph Braat presented the first experiments with erasable compact discs during the 73rd AES Convention . In June 1985, the computer-readable CD-ROM (read-only memory) and, in 1990, recordable CD-R discs were introduced. Recordable CDs became an alternative to tape for recording and distributing music and could be duplicated without degradation in sound quality. Other newer video formats such as DVD and Blu-ray use

7680-444: The CD, the optical parameters, deviations and error rate, modulation system ( eight-to-fourteen modulation , EFM) and error correction facility (CIRC), and the eight subcode channels . These parameters are common to all compact discs and used by all logical formats: audio CD, CD-ROM , etc. The standard also specifies the form of digital audio encoding. The first edition of the Red Book was released in 1980 by Philips and Sony; it

7808-632: The CD. CIRC encoding plus the subcode byte generates 33-byte long frames, called channel-data frames. These frames are then modulated through eight-to-fourteen modulation (EFM), where each 8-bit byte is replaced with a corresponding 14-bit word designed to reduce the number of transitions between 0 and 1. This reduces the density of physical pits on the disc and provides an additional degree of error tolerance. Three merging bits are added before each 14-bit word for disambiguation and synchronization. In total, there are 33 × (14 + 3) = 561 bits. A 27-bit word (a 24-bit pattern plus 3 merging bits)

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7936-475: The DAC. Even when using high-precision components, this approach was prone to decoding errors. Another issue was jitter , a time-related defect. Confronted with the instability of DACs, manufacturers initially turned to increasing the number of bits in the DAC and using several DACs per audio channel, averaging their output. This increased the cost of CD players but did not solve the core problem. A breakthrough in

8064-664: 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 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

8192-451: The US for the first time since 2004, with Axios citing its rise to "young people who are finding they like hard copies of music in the digital age". It came at the same time as both vinyl and cassette reached sales levels not seen in 30 years. The RIAA reported that CD revenue made a dip in 2022, before increasing again in 2023 and overtook downloading for the first time in over a decade. In

8320-477: The US, 33.4 million CD albums were sold in the year 2022. In France in 2023, 10.5 million CDs were sold, almost double that of vinyl, but both of them represented generated 12% each of the French music industry revenues. Sony and Philips received praise for the development of the compact disc from professional organizations. These awards include: The Red Book specifies the physical parameters and properties of

8448-464: 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 the company he founded, Gauss Electrophysics. The LaserDisc was the immediate precursor to the CD, with the primary difference being that

8576-620: The United States. By 2015, only 24% of music in the United States was purchased on physical media, two thirds of this consisting of CDs; however, in the same year in Japan, over 80% of music was bought on CDs and other physical formats. In 2018, U.S. CD sales were 52 million units—less than 6% of the peak sales volume in 2000. In the UK, 32 million units were sold, almost 100 million fewer than in 2008. In 2018, Best Buy announced plans to decrease their focus on CD sales, however, while continuing to sell records, sales of which are growing during

8704-486: The United States. Some computers that were marketed in 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

8832-526: The Who , to be re-released on a single disc. Playing times beyond 74 minutes are achieved by decreasing track pitch (the distance separating the track as it spirals the disc). However, most players can still accommodate the more closely spaced data if it is still within Red Book tolerances. Manufacturing processes used in the final years of CD technology allowed an audio CD to contain up to 98 minutes (variable from one replication plant to another) without requiring

8960-527: The audio (two bytes × two channels × six samples = 24 bytes), eight CIRC error-correction bytes, and one subcode byte. As described in the "Data encoding" section, after the EFM modulation the number of bits in a frame totals 588. On a Red Book audio CD, data is addressed using the MSF scheme , with timecodes expressed in minutes, seconds and another type of frames (mm:ss:ff), where one frame corresponds to 1/75 of

9088-445: The audio frames throughout the disc over several consecutive frames so that the information will be more resistant to burst errors . Therefore, a physical frame on the disc will actually contain information from multiple logical audio frames. This process adds 64 bits of error correction codes to each frame. After this, 8 bits of subcode data are added to each of these encoded frames, which is used for control and addressing when playing

9216-406: 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

9344-399: The bottleneck. The introduction of high-level programming languages in 1958 hid the details of the hardware and expressed the underlying algorithms into the code . Early languages include Fortran , Lisp , and COBOL . There are two main types of software: Software can also be categorized by how it is deployed . Traditional applications are purchased with a perpetual license for

9472-450: The compact disc has been credited to the cooperation between Philips and Sony, which together agreed upon and developed compatible hardware. The unified design of the compact disc allowed consumers to purchase any disc or player from any company and allowed the CD to dominate the at-home music market unchallenged. In 1974, Lou Ottens, director of the audio division of Philips, started a small group to develop an analog optical audio disc with

9600-419: The content creator to sign a waiver releasing the plant owner from responsibility if the CD produced is marginally or entirely unreadable by some playback equipment. In this final practice, maximum CD playing time crept higher by reducing minimum engineering tolerances. Each audio sample is a signed 16-bit two's complement integer , which has sample values ranging from −32768 to +32767. The source audio data

9728-404: The correctness of code, while user acceptance testing helps to ensure that the product meets customer expectations. There are a variety of software development methodologies , which vary from completing all steps in order to concurrent and iterative models. Software development is driven by requirements taken from prospective users, as opposed to maintenance, which is driven by events such as

9856-400: The cost of poor quality software can be as high as 20 to 40 percent of sales. Despite developers' goal of delivering a product that works entirely as intended, virtually all software contains bugs. The rise of the Internet also greatly increased the need for computer security as it enabled malicious actors to conduct cyberattacks remotely. If a bug creates a security risk, it is called

9984-419: The cost of products. Unlike copyrights, patents generally only apply in the jurisdiction where they were issued. Engineer Capers Jones writes that "computers and software are making profound changes to every aspect of human life: education, work, warfare, entertainment, medicine, law, and everything else". It has become ubiquitous in everyday life in developed countries . In many cases, software augments

10112-423: 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

10240-503: 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

10368-423: The diagonal of an audio cassette. Heitaro Nakajima , who developed an early digital audio recorder within Japan's national public broadcasting organization, NHK , in 1970, became general manager of Sony's audio department in 1971. In 1973, his team developed a digital PCM adaptor that made audio recordings using a Betamax video recorder. After this, in 1974 the leap to storing digital audio on an optical disc

10496-401: 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

10624-480: The disc's table of contents (TOC), which provides an index of the start positions of the tracks in the program area and of the lead-out. The track positions are referenced by absolute timecode , relative to the start of the program area, in MSF format: minutes, seconds, and fractional seconds called frames . Each timecode frame is one seventy-fifth of a second, and corresponds to a block of 98 channel-data frames—ultimately,

10752-463: The first four UK albums by the Beatles were released in mono on compact disc. The growing acceptance of the CD in 1983 marks the beginning of the popular digital audio revolution. It was enthusiastically received, especially in the early-adopting classical music and audiophile communities, and its handling quality received particular praise. As the price of players gradually came down, and with

10880-438: The form of commercial off-the-shelf (COTS) or open-source software . Software quality assurance is typically a combination of manual code review by other engineers and automated software testing . Due to time constraints, testing cannot cover all aspects of the software's intended functionality, so developers often focus on the most critical functionality. Formal methods are used in some safety-critical systems to prove

11008-813: The format included: The first artist to sell a million copies on CD was Dire Straits , with their 1985 album Brothers in Arms . One of the first CD markets was devoted to reissuing popular music whose commercial potential was already proven. The first major artist to have their entire catalog converted to CD was David Bowie , whose first fourteen studio albums (up to Scary Monsters (and Super Creeps) ) of (then) sixteen were made available by RCA Records in February 1985, along with four greatest hits albums; his fifteenth and sixteenth albums ( Let's Dance and Tonight , respectively) had already been issued on CD by EMI Records in 1983 and 1984, respectively. On 26 February 1987,

11136-439: The functionality of existing technologies such as household appliances and elevators . Software also spawned entirely new technologies such as the Internet , video games , mobile phones , and GPS . New methods of communication, including email , forums , blogs , microblogging , wikis , and social media , were enabled by the Internet. Massive amounts of knowledge exceeding any paper-based library are now available with

11264-570: The hardware. The introduction of high-level programming languages in 1958 allowed for more human-readable instructions, making software development easier and more portable across different computer architectures . Software in a programming language is run through a compiler or interpreter to execute on the architecture's hardware. Over time, software has become complex, owing to developments in networking , operating systems , and databases . Software can generally be categorized into two main types: The rise of cloud computing has introduced

11392-545: 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

11520-576: The increase was motivated by technical considerations and that even after the increase in size, the Furtwängler recording would not have fit onto one of the earliest CDs. According to a Sunday Tribune interview, the story is slightly more involved. In 1979, Philips owned PolyGram , one of the world's largest music distributors. PolyGram had set up a large experimental CD plant in Hannover , Germany, which could produce huge numbers of CDs having

11648-565: The information for extensions that is available in the Red Book , such as the details for CD-Text , CD+G and CD+EG . The standard is not freely available and must be licensed. It is available from Philips and the IEC. As of 2013 , Philips outsources licensing of the standard to Adminius , which charges US$ 100 for the Red Book , plus US$ 50 each for the Subcode Channels R-W and CD Text Mode annexes. The audio contained in

11776-505: The introduction of the portable Discman , the CD began to gain popularity in the larger popular and rock music markets. With the rise in CD sales, pre-recorded cassette tape sales began to decline in the late 1980s; CD sales overtook cassette sales in the early 1990s. In 1988, 400 million CDs were manufactured by 50 pressing plants around the world. Early CD players employed binary-weighted digital-to-analog converters (DAC), which contained individual electrical components for each bit of

11904-428: The late 1980s culminated in development of the 1-bit DAC , which converts high-resolution low-frequency digital input signal into a lower-resolution high-frequency signal that is mapped to voltages and then smoothed with an analog filter. The temporary use of a lower-resolution signal simplified circuit design and improved efficiency, which is why it became dominant in CD players starting from the early 1990s. Philips used

12032-673: 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

12160-597: The mid-1970s and is vested in the company that makes the software, not the employees or contractors who wrote it. The use of most software is governed by an agreement ( software license ) between the copyright holder and the user. Proprietary software is usually sold under a restrictive license that limits copying and reuse (often enforced with tools such as digital rights management (DRM)). Open-source licenses , in contrast, allow free use and redistribution of software with few conditions. Most open-source licenses used for software require that modifications be released under

12288-465: The music industry, audio CDs have been generally sold as either a CD single (now largely dormant), or as full-length albums , the latter of which has been more commonplace since the 2000s. The format has also been influential in the progression of video game music , used in mixed mode CD-ROMs , providing CD-quality audio popularized during the 1990s on hardware such as PlayStation , Sega Saturn and personal computers with 16-bit sound cards like

12416-632: The new software delivery model Software as a Service (SaaS). In SaaS, applications are hosted by a provider and accessed over the Internet . The process of developing software involves several stages. The stages include software design , programming , testing , release , and maintenance . Software quality assurance and security are critical aspects of software development, as bugs and security vulnerabilities can lead to system failures and security breaches. Additionally, legal issues such as software licenses and intellectual property rights play

12544-472: The operating system) can take this saved file and execute it as a process on the computer hardware. Some programming languages use an interpreter instead of a compiler. An interpreter converts the program into machine code at run time , which makes them 10 to 100 times slower than compiled programming languages. Software is often released with the knowledge that it is incomplete or contains bugs. Purchasers knowingly buy it in this state, which has led to

12672-412: 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

12800-479: 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

12928-432: 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

13056-576: 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

13184-461: 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

13312-555: The physical world may also be part of the requirements for a software patent to be held valid. Software patents have been historically controversial . Before the 1998 case State Street Bank & Trust Co. v. Signature Financial Group, Inc. , software patents were generally not recognized in the United States. In that case, the Supreme Court decided that business processes could be patented. Patent applications are complex and costly, and lawsuits involving patents can drive up

13440-535: 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

13568-438: The pregap as index 0 (this latter usage will result in the track playing as the time counter counts down to time 0:00 at the start of the track, index 1.) This is also the case with some discs offering "101 sound effects", with 100 and 101 being indexed as two and three on track 99. The index, if used, is occasionally put on the track listing as a decimal part of the track number, such as 99.2 or 99.3. ( Information Society 's Hack

13696-451: The prior art by Optophonie and James Russell, the information on the disc is read from a reflective layer using a laser as a light source through a protective substrate. Prototypes were developed by Philips and Sony independently in the late 1970s. Although originally dismissed by Philips Research management as a trivial pursuit, the CD became the primary focus for Philips as the LaserDisc format struggled. In 1979, Sony and Philips set up

13824-408: The release. Over time, the level of maintenance becomes increasingly restricted before being cut off entirely when the product is withdrawn from the market. As software ages , it becomes known as legacy software and can remain in use for decades, even if there is no one left who knows how to fix it. Over the lifetime of the product, software maintenance is estimated to comprise 75 percent or more of

13952-424: The same license, which can create complications when open-source software is reused in proprietary projects. Patents give an inventor an exclusive, time-limited license for a novel product or process. Ideas about what software could accomplish are not protected by law and concrete implementations are instead covered by copyright law . In some countries, a requirement for the claimed invention to have an effect on

14080-432: The same physical geometry as CD, and most DVD and Blu-ray players are backward compatible with audio CDs. CD sales in the United States peaked by 2000. By the early 2000s, the CD player had largely replaced the audio cassette player as standard equipment in new automobiles, with 2010 being the final model year for any car in the United States to have a factory-equipped cassette player. Two new formats were marketed in

14208-575: 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

14336-484: 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 ,

14464-511: The standard in 1996. Philips coined the term compact disc in line with another audio product, the Compact Cassette , and contributed the general manufacturing process , based on video LaserDisc technology. Philips also contributed eight-to-fourteen modulation (EFM), while Sony contributed the error-correction method, CIRC, which offers resilience to defects such as scratches and fingerprints. The Compact Disc Story , told by

14592-467: 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

14720-431: The total development cost. Completing a software project involves various forms of expertise, not just in software programmers but also testing, documentation writing, project management , graphic design , user experience , user support, marketing , and fundraising. Software quality is defined as meeting the stated requirements as well as customer expectations. Quality is an overarching term that can refer to

14848-604: The underspecified "four-channel" mode was dropped from the CD standard when it was adopted by the International Electrotechnical Commission and became IEC 908:1987, and later IEC 60908:1999. Since the behavior of the "four-channel" or "Broadcasting use" bit was never specified by either CD standard, no mass-marketed discs have attempted to use the Red Book's four-channel mode, and no players have purported to implement it. The creators of

14976-407: 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,

15104-463: 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

15232-482: Was adopted by the Digital Audio Disc Committee and ratified by the International Electrotechnical Commission (IEC) Technical Committee 100 as an international standard in 1987 with the reference IEC 60908. The second edition of IEC 60908 was published in 1999 and it replaces the first edition, amendment 1 (1992) and the corrigendum to amendment 1. The IEC 60908 however does not contain all

15360-464: Was easily made. Sony first publicly demonstrated an optical digital audio disc in September 1976. A year later, in September 1977, Sony showed the press a 30 cm (12 in) disc that could play an hour of digital audio (44,100 Hz sampling rate and 16-bit resolution) using modified frequency modulation encoding. In September 1978, the company demonstrated an optical digital audio disc with

15488-461: Was granted a patent in 1970. Following litigation, Sony and Philips licensed Russell's patents for recording in 1988. It is debatable whether Russell's concepts, patents, and prototypes instigated and in some measure influenced the compact disc's design. The compact disc is an evolution of LaserDisc technology, where a focused laser beam is used that enables the high information density required for high-quality digital audio signals. Unlike

15616-522: 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

15744-468: 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

15872-1085: 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.

16000-486: Was one of very few CD releases to do this, following a release with an equally obscure CD+G feature.) The track and index structure of the CD were carried forward to the DVD format as title and chapter, respectively. Tracks, in turn, are divided into timecode frames (or sectors), which are further subdivided into channel-data frames. The smallest entity in a CD is a channel-data frame , which consists of 33 bytes and contains six complete 16-bit stereo samples: 24 bytes for

16128-458: Was originally intended to be included in CD-DA. The Red Book specification briefly mentioned a four-channel mode in its June 1980, September 1983, and November 1991 editions. On the first page, it lays out the "Main parameters" of the CD system, including: "Number of channels: 2 and/or 4 simultaneously[*] sampled." The footnote says, "In the case of more than two channels the encoder and decoder diagrams have to be adapted." In reality, however,

16256-514: Was published on 1 March 1979. A week later, on 8 March, Philips publicly demonstrated a prototype of an optical digital audio disc at a press conference called "Philips Introduce Compact Disc" in Eindhoven , Netherlands. Sony executive Norio Ohga , later CEO and chairman of Sony, and Heitaro Nakajima were convinced of the format's commercial potential and pushed further development despite widespread skepticism. In 1979, Sony and Philips set up

16384-401: Was simultaneous with the compilers needed to translate them automatically into machine code. Most programs do not contain all the resources needed to run them and rely on external libraries . Part of the compiler's function is to link these files in such a way that the program can be executed by the hardware. Once compiled, the program can be saved as an object file and the loader (part of

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