1.
Software developer
–
A software developer is a person concerned with facets of the software development process, including the research, design, programming, and testing of computer software. Other job titles which are used with similar meanings are programmer, software analyst. According to developer Eric Sink, the differences between system design, software development, and programming are more apparent, even more so that developers become systems architects, those who design the multi-leveled architecture or component interactions of a large software system. In a large company, there may be employees whose sole responsibility consists of one of the phases above. In smaller development environments, a few people or even an individual might handle the complete process. The word software was coined as a prank as early as 1953, before this time, computers were programmed either by customers, or the few commercial computer vendors of the time, such as UNIVAC and IBM. The first company founded to provide products and services was Computer Usage Company in 1955. The software industry expanded in the early 1960s, almost immediately after computers were first sold in mass-produced quantities, universities, government, and business customers created a demand for software. Many of these programs were written in-house by full-time staff programmers, some were distributed freely between users of a particular machine for no charge. Others were done on a basis, and other firms such as Computer Sciences Corporation started to grow. The computer/hardware makers started bundling operating systems, systems software and programming environments with their machines, new software was built for microcomputers, so other manufacturers including IBM, followed DECs example quickly, resulting in the IBM AS/400 amongst others. The industry expanded greatly with the rise of the computer in the mid-1970s. In the following years, it created a growing market for games, applications. DOS, Microsofts first operating system product, was the dominant operating system at the time, by 2014 the role of cloud developer had been defined, in this context, one definition of a developer in general was published, Developers make software for the world to use. The job of a developer is to crank out code -- fresh code for new products, code fixes for maintenance, code for business logic, bus factor Software Developer description from the US Department of Labor
2.
International Organization for Standardization
–
The International Organization for Standardization is an international standard-setting body composed of representatives from various national standards organizations. Founded on 23 February 1947, the organization promotes worldwide proprietary and it is headquartered in Geneva, Switzerland, and as of March 2017 works in 162 countries. It was one of the first organizations granted general consultative status with the United Nations Economic, ISO, the International Organization for Standardization, is an independent, non-governmental organization, the members of which are the standards organizations of the 162 member countries. It is the worlds largest developer of international standards and facilitates world trade by providing common standards between nations. Nearly twenty thousand standards have been set covering everything from manufactured products and technology to food safety, use of the standards aids in the creation of products and services that are safe, reliable and of good quality. The standards help businesses increase productivity while minimizing errors and waste, by enabling products from different markets to be directly compared, they facilitate companies in entering new markets and assist in the development of global trade on a fair basis. The standards also serve to safeguard consumers and the end-users of products and services, the three official languages of the ISO are English, French, and Russian. The name of the organization in French is Organisation internationale de normalisation, according to the ISO, as its name in different languages would have different abbreviations, the organization adopted ISO as its abbreviated name in reference to the Greek word isos. However, during the meetings of the new organization, this Greek word was not invoked. Both the name ISO and the logo are registered trademarks, the organization today known as ISO began in 1926 as the International Federation of the National Standardizing Associations. ISO is an organization whose members are recognized authorities on standards. Members meet annually at a General Assembly to discuss ISOs strategic objectives, the organization is coordinated by a Central Secretariat based in Geneva. A Council with a membership of 20 member bodies provides guidance and governance. The Technical Management Board is responsible for over 250 technical committees, ISO has formed joint committees with the International Electrotechnical Commission to develop standards and terminology in the areas of electrical and electronic related technologies. Information technology ISO/IEC Joint Technical Committee 1 was created in 1987 to evelop, maintain, ISO has three membership categories, Member bodies are national bodies considered the most representative standards body in each country. These are the members of ISO that have voting rights. Correspondent members are countries that do not have their own standards organization and these members are informed about ISOs work, but do not participate in standards promulgation. Subscriber members are countries with small economies and they pay reduced membership fees, but can follow the development of standards
3.
Ecma International
–
ECMA is a standards organization for information and communication systems. It acquired its current name in 1994, when the European Computer Manufacturers Association changed its name to reflect the global reach. As a consequence, the name is no longer considered an acronym, the organization was founded in 1961 to standardize computer systems in Europe. Ecma publications, including standards, can be copied by all interested parties without copyright restrictions. The development of standards and technical reports is done in co-operation with the national, European. Unlike national standardization bodies, Ecma is a membership-based organization and it takes pride in the resulting business-like approach to standards, claimed to lead to better standards in less time, thanks to a less bureaucratic process focused on achieving results by consensus. Ecma has actively contributed to worldwide standardization in information technology and telecommunications, more than 400 Ecma Standards and 100 Technical Reports have been published, more than 2/3 of which have also been adopted as international standards and/or technical reports. The memberlist of Ecma International is available on its website, thus, Ecma is not responsible for the standardization of Java. Ecma is involved in the standardization of the Ecma Office Open XML format based on the XML office document formats by Microsoft, the Ecma Office Open XML maintenance process is performed by technical committee 45
4.
Master boot record
–
The concept of MBRs was publicly introduced in 1983 with PC DOS2.0 operating system. The MBR holds the information on how the partitions, containing file systems, are organized on that medium. This MBR code is referred to as a boot loader. The organization of the table in the MBR limits the maximum addressable storage space of a disk to 2 TiB. Therefore, the MBR-based partitioning scheme is in the process of being superseded by the GUID Partition Table scheme in new computers, a GPT can coexist with an MBR in order to provide some limited form of backward compatibility for older systems. MBRs are not present on non-partitioned media such as floppies, superfloppies or other storage devices configured to behave as such, the original version of the MBR was written by David Litton of IBM in June 1982. The partition table supported up to four primary partitions, of which DOS could only use one and this did not change when FAT16 was introduced as a new file system with DOS3.0. In 1996, support for logical block addressing was introduced in Windows 95B and this also reflected the idea that the MBR is meant to be operating system and file system independent. This was even to the extent of being supported by operating systems for other platforms. Sometimes this was in addition to other pre-existing or cross-platform standards for bootstrapping and partitioning, MBR partition entries and the MBR boot code used in commercial operating systems, however, are limited to 32 bits. Therefore, the disk size supported on disks using 512-byte sectors by the MBR partitioning scheme is limited to 2 TiB. Consequently, a different partitioning scheme must be used for larger disks, the MBR partitioning scheme is therefore in the process of being superseded by the GUID Partition Table. The official approach does little more than ensuring data integrity by employing a protective MBR, specifically, it does not provide backward compatibility with operating systems that do not support the GPT scheme as well. The present non-standard nature of these solutions causes various compatibility problems in certain scenarios, the MBR consists of 512 or more bytes located in the first sector of the drive. It may contain one or more of, A partition table describing the partitions of a storage device, in this context the boot sector may also be called a partition sector. Bootstrap code, Instructions to identify the configured bootable partition, then load, IBM PC DOS2.0 introduced the FDISK utility to set up and maintain MBR partitions. The partitions themselves may also contain data to more complex partitioning schemes, such as extended boot records, BSD disklabels. The MBR is not located in a partition, it is located at a first sector of the device, preceding the first partition
5.
GUID Partition Table
–
All modern PC operating systems support GPT. The widespread MBR partitioning scheme, dating from the early 1980s, one of the main limitations is the usage of 32 bits for storing block addresses and quantity information. For hard disks with 512-byte sectors, the MBR partition table entries allow up to a maximum of 2 TiB, intel therefore developed a new partition table format in the late 1990s as part of what eventually became UEFI. As of 2010, GPT forms a subset of the UEFI specification, GPT allocates 64 bits for logical block addresses, therefore allowing a maximum disk size of 264 sectors. For disks with 512-byte sectors, maximum size is 9.4 ZB or 8 ZiB, mBR-based partition table schemes insert the partitioning information for four primary partitions in the MBR. Like modern MBRs, GPTs use logical block addressing in place of the historical cylinder-head-sector addressing. The protective MBR is contained in LBA0, the GPT header is in LBA1, the UEFI specification stipulates that a minimum of 16,384 bytes, regardless of sector size, be allocated for the Partition Entry Array. On a disk having 512-byte sectors, a partition entry array size of 16,384 bytes, hard-disk manufacturers are transitioning to 4, 096-byte sectors. This was a problem on writes, when the drive is forced to perform two read-modify-write operations to satisfy a single misaligned 4 KB write operation. This is also true of partitions with emulated CHS geometries or partitions accessed only via LBA, extended partitions must start on cylinder boundaries as well. That otherwise unused space is commonly used by bootloaders such as GRUB for storing their second stages. This is referred to as a protective MBR, a single partition type of EEh, encompassing the entire GPT drive, is indicated and identifies it as GPT. While the MBR and protective MBR layouts were defined around 512 bytes per sector, extra space in the MBR typically remains unused. This amounts to a maximum reported size of 2 TB, assuming a disk with 512 bytes per sector, the bootloader in the MBR must not assume a sector size of 512 bytes. The partition table header defines the usable blocks on the disk and it also defines the number and size of the partition entries that make up the partition table. The EFI stipulates a minimum of 16,384 bytes be reserved for the partition table array, so there are 128 partition entries reserved, the header contains the disk GUID. It records its own size and location and the size and location of the secondary GPT header, importantly, it also contains a CRC32 checksum for itself and for the partition table, which may be verified by the firmware, bootloader, or operating system on boot. Because of this, hex editors should not be used to modify the contents of the GPT, such modification would render the checksum invalid
6.
Unicode
–
Unicode is a computing industry standard for the consistent encoding, representation, and handling of text expressed in most of the worlds writing systems. As of June 2016, the most recent version is Unicode 9.0, the standard is maintained by the Unicode Consortium. Unicodes success at unifying character sets has led to its widespread, the standard has been implemented in many recent technologies, including modern operating systems, XML, Java, and the. NET Framework. Unicode can be implemented by different character encodings, the most commonly used encodings are UTF-8, UTF-16 and the now-obsolete UCS-2. UTF-8 uses one byte for any ASCII character, all of which have the same values in both UTF-8 and ASCII encoding, and up to four bytes for other characters. UCS-2 uses a 16-bit code unit for each character but cannot encode every character in the current Unicode standard, UTF-16 extends UCS-2, using one 16-bit unit for the characters that were representable in UCS-2 and two 16-bit units to handle each of the additional characters. Many traditional character encodings share a common problem in that they allow bilingual computer processing, Unicode, in intent, encodes the underlying characters—graphemes and grapheme-like units—rather than the variant glyphs for such characters. In the case of Chinese characters, this leads to controversies over distinguishing the underlying character from its variant glyphs. In text processing, Unicode takes the role of providing a unique code point—a number, in other words, Unicode represents a character in an abstract way and leaves the visual rendering to other software, such as a web browser or word processor. This simple aim becomes complicated, however, because of concessions made by Unicodes designers in the hope of encouraging a more rapid adoption of Unicode, the first 256 code points were made identical to the content of ISO-8859-1 so as to make it trivial to convert existing western text. For other examples, see duplicate characters in Unicode and he explained that he name Unicode is intended to suggest a unique, unified, universal encoding. In this document, entitled Unicode 88, Becker outlined a 16-bit character model, Unicode could be roughly described as wide-body ASCII that has been stretched to 16 bits to encompass the characters of all the worlds living languages. In a properly engineered design,16 bits per character are more than sufficient for this purpose, Unicode aims in the first instance at the characters published in modern text, whose number is undoubtedly far below 214 =16,384. By the end of 1990, most of the work on mapping existing character encoding standards had been completed, the Unicode Consortium was incorporated in California on January 3,1991, and in October 1991, the first volume of the Unicode standard was published. The second volume, covering Han ideographs, was published in June 1992, in 1996, a surrogate character mechanism was implemented in Unicode 2.0, so that Unicode was no longer restricted to 16 bits. The Microsoft TrueType specification version 1.0 from 1992 used the name Apple Unicode instead of Unicode for the Platform ID in the naming table, Unicode defines a codespace of 1,114,112 code points in the range 0hex to 10FFFFhex. Normally a Unicode code point is referred to by writing U+ followed by its hexadecimal number, for code points in the Basic Multilingual Plane, four digits are used, for code points outside the BMP, five or six digits are used, as required. Code points in Planes 1 through 16 are accessed as surrogate pairs in UTF-16, within each plane, characters are allocated within named blocks of related characters
7.
Operating system
–
An operating system is system software that manages computer hardware and software resources and provides common services for computer programs. All computer programs, excluding firmware, require a system to function. Operating systems are found on many devices that contain a computer – from cellular phones, the dominant desktop operating system is Microsoft Windows with a market share of around 83. 3%. MacOS by Apple Inc. is in place, and the varieties of Linux is in third position. Linux distributions are dominant in the server and supercomputing sectors, other specialized classes of operating systems, such as embedded and real-time systems, exist for many applications. A single-tasking system can run one program at a time. Multi-tasking may be characterized in preemptive and co-operative types, in preemptive multitasking, the operating system slices the CPU time and dedicates a slot to each of the programs. Unix-like operating systems, e. g. Solaris, Linux, cooperative multitasking is achieved by relying on each process to provide time to the other processes in a defined manner. 16-bit versions of Microsoft Windows used cooperative multi-tasking, 32-bit versions of both Windows NT and Win9x, used preemptive multi-tasking. Single-user operating systems have no facilities to distinguish users, but may allow multiple programs to run in tandem, a distributed operating system manages a group of distinct computers and makes them appear to be a single computer. The development of networked computers that could be linked and communicate with each other gave rise to distributed computing, distributed computations are carried out on more than one machine. When computers in a work in cooperation, they form a distributed system. The technique is used both in virtualization and cloud computing management, and is common in large server warehouses, embedded operating systems are designed to be used in embedded computer systems. They are designed to operate on small machines like PDAs with less autonomy and they are able to operate with a limited number of resources. They are very compact and extremely efficient by design, Windows CE and Minix 3 are some examples of embedded operating systems. A real-time operating system is a system that guarantees to process events or data by a specific moment in time. A real-time operating system may be single- or multi-tasking, but when multitasking, early computers were built to perform a series of single tasks, like a calculator. Basic operating system features were developed in the 1950s, such as resident monitor functions that could run different programs in succession to speed up processing
8.
File system
–
In computing, a file system or filesystem is used to control how data is stored and retrieved. Without a file system, information placed in a storage medium would be one large body of data with no way to tell where one piece of information stops, by separating the data into pieces and giving each piece a name, the information is easily isolated and identified. Taking its name from the way paper-based information systems are named, the structure and logic rules used to manage the groups of information and their names is called a file system. There are many different kinds of file systems, each one has different structure and logic, properties of speed, flexibility, security, size and more. Some file systems have been designed to be used for specific applications, for example, the ISO9660 file system is designed specifically for optical discs. File systems can be used on different types of storage devices that use different kinds of media. The most common device in use today is a hard disk drive. Other kinds of media that are used include flash memory, magnetic tapes, in some cases, such as with tmpfs, the computers main memory is used to create a temporary file system for short-term use. Some file systems are used on local storage devices, others provide file access via a network protocol. Some file systems are virtual, meaning that the files are computed on request or are merely a mapping into a different file system used as a backing store. The file system access to both the content of files and the metadata about those files. It is responsible for arranging storage space, reliability, efficiency, before the advent of computers the term file system was used to describe a method of storing and retrieving paper documents. By 1961 the term was being applied to computerized filing alongside the original meaning, by 1964 it was in general use. A file system consists of two or three layers, sometimes the layers are explicitly separated, and sometimes the functions are combined. The logical file system is responsible for interaction with the user application and it provides the application program interface for file operations — OPEN, CLOSE, READ, etc. and passes the requested operation to the layer below it for processing. The logical file system manage open file table entries and per-process file descriptors and this layer provides file access, directory operations, security and protection. The second optional layer is the file system. This interface allows support for multiple concurrent instances of physical file systems, the third layer is the physical file system
9.
Computer data storage
–
Computer data storage, often called storage or memory, is a technology consisting of computer components and recording media used to retain digital data. It is a function and fundamental component of computers. The central processing unit of a computer is what manipulates data by performing computations, in practice, almost all computers use a storage hierarchy, which puts fast but expensive and small storage options close to the CPU and slower but larger and cheaper options farther away. In the Von Neumann architecture, the CPU consists of two parts, The control unit and the arithmetic logic unit. The former controls the flow of data between the CPU and memory, while the latter performs arithmetic and logical operations on data, without a significant amount of memory, a computer would merely be able to perform fixed operations and immediately output the result. It would have to be reconfigured to change its behavior and this is acceptable for devices such as desk calculators, digital signal processors, and other specialized devices. Von Neumann machines differ in having a memory in which they store their operating instructions, most modern computers are von Neumann machines. A modern digital computer represents data using the numeral system. Text, numbers, pictures, audio, and nearly any form of information can be converted into a string of bits, or binary digits. The most common unit of storage is the byte, equal to 8 bits, a piece of information can be handled by any computer or device whose storage space is large enough to accommodate the binary representation of the piece of information, or simply data. For example, the works of Shakespeare, about 1250 pages in print. Data is encoded by assigning a bit pattern to each character, digit, by adding bits to each encoded unit, redundancy allows the computer to both detect errors in coded data and correct them based on mathematical algorithms. A random bit flip is typically corrected upon detection, the cyclic redundancy check method is typically used in communications and storage for error detection. A detected error is then retried, data compression methods allow in many cases to represent a string of bits by a shorter bit string and reconstruct the original string when needed. This utilizes substantially less storage for many types of data at the cost of more computation, analysis of trade-off between storage cost saving and costs of related computations and possible delays in data availability is done before deciding whether to keep certain data compressed or not. For security reasons certain types of data may be encrypted in storage to prevent the possibility of unauthorized information reconstruction from chunks of storage snapshots. Generally, the lower a storage is in the hierarchy, the lesser its bandwidth and this traditional division of storage to primary, secondary, tertiary and off-line storage is also guided by cost per bit. In contemporary usage, memory is usually semiconductor storage read-write random-access memory, typically DRAM or other forms of fast but temporary storage
10.
DVD
–
DVD is a digital optical disc storage format invented and developed by Philips, Sony, Toshiba, and Panasonic in 1995. The medium can store any kind of data and is widely used for software. DVDs offer higher capacity than compact discs while having the same dimensions. Pre-recorded DVDs are mass-produced using molding machines that physically stamp data onto the DVD, such discs are a form of DVD-ROM because data can only be read and not written or erased. Blank recordable DVD discs can be recorded using a DVD recorder. Rewritable DVDs can be recorded and erased many times, DVDs containing other types of information may be referred to as DVD data discs. The OED also states that in 1995, The companies said the name of the format will simply be DVD. Toshiba had been using the name ‘digital video disk’, but that was switched to ‘digital versatile disk’ after computer companies complained that it left out their applications, Digital versatile disc is the explanation provided in a DVD Forum Primer from 2000 and in the DVD Forums mission statement. There were several formats developed for recording video on optical discs before the DVD, Optical recording technology was invented by David Paul Gregg and James Russell in 1958 and first patented in 1961. A consumer optical disc data format known as LaserDisc was developed in the United States and it used much larger discs than the later formats. CD Video used analog video encoding on optical discs matching the established standard 120 mm size of audio CDs, Video CD became one of the first formats for distributing digitally encoded films in this format, in 1993. In the same year, two new optical disc formats were being developed. By the time of the launches for both formats in January 1995, the MMCD nomenclature had been dropped, and Philips and Sony were referring to their format as Digital Video Disc. Representatives from the SD camp asked IBM for advice on the system to use for their disc. Alan E. Bell, a researcher from IBMs Almaden Research Center, got that request and this group was referred to as the Technical Working Group, or TWG. On August 14,1995, an ad hoc group formed from five computer companies issued a release stating that they would only accept a single format. The TWG voted to both formats unless the two camps agreed on a single, converged standard. They recruited Lou Gerstner, president of IBM, to pressure the executives of the warring factions, as a result, the DVD specification provided a storage capacity of 4.7 GB for a single-layered, single-sided disc and 8.5 GB for a dual-layered, single-sided disc
11.
Optical disc
–
The encoding material sits atop a thicker substrate which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the disc surface. Most optical discs exhibit a characteristic iridescence as a result of the diffraction grating formed by its grooves and this side of the disc contains the actual data and is typically coated with a transparent material, usually lacquer. The reverse side of a disc usually has a printed label, sometimes made of paper. Optical discs are usually between 7.6 and 30 cm in diameter, with 12 cm being the most common size, a typical disc is about 1.2 mm thick, while the track pitch ranges from 1.6 µm to 320 nm. An optical disc is designed to support one of three recording types, read-only, recordable, or re-recordable, write-once optical discs commonly have an organic dye recording layer between the substrate and the reflective layer. Rewritable discs typically contain an alloy recording layer composed of a phase change material, most often AgInSbTe, an alloy of silver, indium, antimony, Optical discs are most commonly used for storing music, video, or data and programs for personal computers. The Optical Storage Technology Association promotes standardized optical storage formats, although optical discs are more durable than earlier audio-visual and data storage formats, they are susceptible to environmental and daily-use damage. Libraries and archives enact optical media preservation procedures to ensure continued usability in the optical disc drive or corresponding disc player. For computer data backup and physical data transfer, optical discs such as CDs and DVDs are gradually being replaced with faster, smaller solid-state devices and this trend is expected to continue as USB flash drives continue to increase in capacity and drop in price. Additionally, music purchased or shared over the Internet has significantly reduced the number of audio CDs sold annually. The first recorded use of an optical disc was in the 1884 when Alexander Graham Bell, Chichester Bell. An early optical disc system existed in 1935, named Lichttonorgel, an early analog optical disc used for video recording was invented by David Paul Gregg in 1958 and patented in the US in 1961 and 1969. This form of optical disc was an early form of the DVD. It is of special interest that U. S, patent 4,893,297, filed 1989, issued 1990, generated royalty income for Pioneer Corporations DVA until 2007 —then encompassing the CD, DVD, and Blu-ray systems. In the early 1960s, the Music Corporation of America bought Greggs patents and his company, american inventor James T. Russell has been credited with inventing the first system to record a digital signal on an optical transparent foil which is lit from behind by a high-power halogen lamp. Russells patent application was first filed in 1966 and he was granted a patent in 1970, following litigation, Sony and Philips licensed Russells patents in the 1980s. Both Greggs and Russells disc are floppy media read in transparent mode, in the Netherlands in 1969, Philips Research physicist, Pieter Kramer invented an optical videodisc in reflective mode with a protective layer read by a focused laser beam U. S
12.
ISO 9660
–
ISO9660 is a file system standard published by the International Organization for Standardization for optical disc media. It aims at supporting different computer operating systems such as Windows, classic Mac OS, ISO9660 traces its roots to the High Sierra Format file system. High Sierra arranged file information in a dense, sequential layout to minimize access by using a hierarchical tree file system arrangement, similar to UNIX. High Sierra was adopted in December 1986 as a standard by Ecma International as ECMA-119 and submitted for fast tracking to the ISO. The following is the overall structure of the ISO9660 file system, The System Area. For example, a CD-ROM may contain a file system descriptor in this area. The data area begins with a set of one or more volume descriptors, collectively the volume descriptor set acts as a header for the data area, describing its content. The volume descriptor set terminator is simply a type of volume descriptor with the purpose of marking the end of this set of structures. Each volume descriptor is 2048 bytes in size, fitting perfectly into a single Mode 1 or Mode 2 Form 1 sector and they have the following structure, The data field of a volume descriptor may be subdivided into several fields, with the exact content depending on the type. The Primary Volume Descriptor provides information about the volume, characteristics and metadata, other fields contain the description or name of the volume, and information about who created it and with which application. The size of the blocks which the file system uses to segment the volume is also stored in a field inside the primary volume descriptor. In addition to the Primary Volume Descriptor, Supplementary Volume Descriptors or Enhanced Volume Descriptors may be present. The standard specifies that ISO2022 is used for managing code sets that are wider than 8 bytes, consequently, ISO9660 supports international single-byte and multi-byte character sets, provided they fit into the framework of the referenced standards. Enhanced Volume Descriptors were introduced in ISO9660, Amendment 1 and they relax some of the requirements of the other volume descriptors and the directory records referenced by them, for example, the directory depth can exceed eight, file identifiers need not contain. Or file version number, the length of a file and directory identifier is maximized to 207, redundant copies of each volume descriptor can also be included in case the first copy of the descriptor becomes corrupt. Directory entries are stored following the location of the directory entry. Both directories and files are stored as extents, which are series of sectors. Files and directories are differentiated only by an attribute that indicates its nature
13.
CD-RW
–
CD-RW is a digital optical disc storage format. A CD-RW disc is a disc that can be written, read arbitrarily many times, erased. The technology was introduced in 1997, CD-RW discs require readers that have more sensitive laser optics than are required to read plain CDs. Consequently, CD-RWs cannot be read in many CD readers built prior to the introduction of CD-RW, CD-ROM drives that bear a MultiRead certification claim compatibility. CD-RW discs need to be blanked before reuse, fast blanking is much quicker, and is usually sufficient to allow rewriting the disc. Full blanking removes traces of the data, often for confidentiality reasons. It may be possible to data from full-blanked CD-RWs with specialty data recovery equipment, however. Their ideal usage field is in the creation of test discs, temporary short or mid-term backups, and in general, the CD-MO standard also allowed for an optional non-erasable zone on the disc, which could be read by normal CD-ROM reader units. Reading of the discs relied on the Kerr effect, the format was never released commercially, mostly because of its inherent incompatibility with standard CD reading units. A similar situation was present for early CD-R media, which suffered from either physical or logical incompatibilities. There were however some magneto-optical drives and media with the form factor that dont have this limitation. Unlike modern CD-RWs, CD-MO allowed for hybrid discs containing both an unmodifiable, pressed section, readable in standard drives, and a writable MO section, other kinds of magneto-optical media, unbound by the limitations of the typical CD-ROM filesystems, took the place intended for CD-MO. Rewritable media can, with hardware, according to some manufacturers. The CD-RW technology is based on phase change technology, so the degree of reflection reached is only 15–25%, the properties of the medium and the write and erase procedure is defined in the Orange Book Part III. To keep rotational speed precise, tracks have a slight superimposed sinusoidal excursion of 0.3 µm at a frequency of 22.05 kHz, in addition a 1 kHz frequency modulation is applied to provide the recorder with an absolute time reference. The grooves have a width of 0.6 µm and pitch of 1.6 µm, the media for CD-RW has basically the same layers as CD-R media. The reflective layer is, however, an alloy, which has in its original state. When writing the laser beam uses its power to heat the material to 500–700 °C
14.
Floppy disk
–
Floppy disks are read and written by a floppy disk drive. Floppy disks, initially as 8-inch media and later in 5¼-inch and 3½-inch sizes, were a form of data storage and exchange from the mid-1970s into the mid-2000s. These formats are usually handled by older equipment and these disks and associated drives were produced and improved upon by IBM and other companies such as Memorex, Shugart Associates, and Burroughs Corporation. The term floppy disk appeared in print as early as 1970, in 1976, Shugart Associates introduced the first 5¼-inch FDD. By 1978 there were more than 10 manufacturers producing such FDDs, there were competing floppy disk formats, with hard- and soft-sector versions and encoding schemes such as FM, MFM and GCR. The 5¼-inch format displaced the 8-inch one for most applications, the most common capacity of the 5¼-inch format in DOS-based PCs was 360 kB and in 1984 IBM introduced the 1.2 MB dual-sided floppy disk along with its PC-AT model. IBM started using the 720 kB double-density 3½-inch microfloppy disk on its Convertible laptop computer in 1986 and these disk drives could be added to older PC models. In 1988 IBM introduced a drive for 2.88 MB DSED diskettes in its top-of-the-line PS/2 models, throughout the early 1980s, limitations of the 5¼-inch format became clear. Originally designed to be practical than the 8-inch format, it was itself too large, as the quality of recording media grew. A number of solutions were developed, with drives at 2-, 2½-, 3-, 3½-, the large market share of the 5¼-inch format made it difficult for these new formats to gain significant market share. A variant on the Sony design, introduced in 1982 by a number of manufacturers, was then rapidly adopted. By the end of the 1980s, 5¼-inch disks had been superseded by 3½-inch disks, by the mid-1990s, 5¼-inch drives had virtually disappeared, as the 3½-inch disk became the predominant floppy disk. Floppy disks became ubiquitous during the 1980s and 1990s in their use with computers to distribute software, transfer data. Before hard disks became affordable to the population, floppy disks were often used to store a computers operating system. Most home computers from that period have a primary OS and BASIC stored as ROM, by the early 1990s, the increasing software size meant large packages like Windows or Adobe Photoshop required a dozen disks or more. In 1996, there were a five billion standard floppy disks in use. Then, distribution of packages was gradually replaced by CD-ROMs, DVDs. External USB-based floppy disk drives are available, many modern systems provide firmware support for booting from such drives
15.
USB flash drive
–
USB flash drives are typically removable and rewritable, and physically much smaller than an optical disc. Most weigh less than 30 grams, since first appearing on the market in late 2000, as with virtually all computer memory devices, storage capacities have risen while prices have dropped. As of March 2016, flash drives with anywhere from 8 to 256 GB are frequently sold, storage capacities as large as 2 TB are planned, with steady improvements in size and price per capacity expected. Some allow up to 100,000 write/erase cycles, depending on the type of memory chip used. USB flash drives are used for the same purposes for which floppy disks or CDs were once used, i. e. for storage, data back-up. They are smaller, faster, have thousands of times more capacity, additionally, they are immune to electromagnetic interference, and are unharmed by surface scratches.44 MB3. 5-inch floppy disk. The USB connector may be protected by a cap or by retracting into the body of the drive. Most flash drives use a standard type-A USB connection allowing connection with a port on a personal computer, USB flash drives draw power from the computer via the USB connection. Some devices combine the functionality of a media player with USB flash storage. Pua Khein-Seng from Malaysia is considered by many to be the Father of Pen Drive and he is notable for incorporating the worlds first single chip USB flash controller. Pua hails from Sekinchan, Selangor, Malaysia, pua founded Phison Electronics based in Taiwan with four other partners and is believed to have produced the worlds first USB flash drive with system-on-chip technology. Competing claims have made by Singaporean company Trek Technology and Chinese company Netac Technology, Both Trek Technology. Trek won a Singaporean suit, but a court in the United Kingdom revoked one of Treks UK patents, Trek Technology and IBM began selling the first USB flash drives commercially in 2000. IBMs USB flash drive became available on December 15,2000, in 2000, Lexar introduced a Compact Flash card with a USB connection, and a companion card read/writer and USB cable that eliminated the need for a USB hub. That is considerably slower than what a hard drive or solid-state drive can achieve when connected via the SATA interface. Transfer rates may be given in megabytes per second, megabits per second, or in optical drive multipliers such as 180X.1, which is limited to 12 Mbit/s with accounted overhead. The effective transfer rate of a device is significantly affected by the access pattern, for example. Like USB2.0 before it, USB3.0 dramatically improved data rates compared to its predecessor
16.
CD-R
–
CD-R is a digital optical disc storage format. A CD-R disc is a disc that can be written once. CD-R disks are readable by most plain CD readers, i. e. CD readers manufactured prior to the introduction of CD-R and this is an advantage over CD-RW, which can be re-written but cannot be played on many plain CD readers. The CD-R, originally named CD Write-Once, specification was first published in 1988 by Philips, the Orange Book consists of several parts, furnishing details of the CD-WO, CD-MO, and CD-RW. The latest editions have abandoned the use of the term CD-WO in favor of CD-R, written CD-Rs and CD-RWs are, in the aspect of low-level encoding and data format, fully compatible with the audio CD and data CD standards. This means they use Eight-to-Fourteen Modulation, CIRC error correction, and, for CD-ROM, properly written CD-R discs on blanks of less than 80 minutes length are fully compatible with the audio CD and CD-ROM standards in all details including physical specifications. 80 minute CD-R discs marginally violate the Red Book physical format specifications, CD-RW discs have lower reflectivity than CD-R or pressed CDs and for this reason cannot meet the Red Book standard. Some hardware compatible with Red Book CDs may have difficulty reading CD-Rs and, because of their lower reflectivity, especially CD-RWs. To the extent that CD hardware can read extended-length discs or CD-RW discs, it is because that hardware has capability beyond the minimum required by the Red Book and Yellow Book standards. The dye materials developed by Taiyo Yuden made it possible for CD-R discs to be compatible with Audio CD, a standard CD-R is a 1.2 mm thick disc made of polycarbonate about 120 mm or 80 mm diameter. The 120 mm disc has a capacity of 74 minutes of audio or 650 Megabytes of data. Despite the foregoing, most CD-Rs on the market have an 80-minute capacity, there are also 90 minute/790 MiB and 99 minute/870 MiB discs, although they are less common. Also, due to the limitations of the structures in the ATIP,90 and 99 minute blanks will identify as 80 minute ones. Therefore, in order to use the capacity, these discs have to be burned using overburn options in the CD recording software. Nothing in the Red, Yellow or Orange Book standards prohibits disc reading/writing devices from having the capacity to read or write discs beyond the Compact Disc standards, the polycarbonate disc contains a spiral groove, called the pregroove, to guide the laser beam upon writing and reading information. The polycarbonate disc is coated on the side with a very thin layer of organic dye. Then, on top of the dye is coated a thin, reflecting layer of silver, finally, a protective coating of a photo-polymerizable lacquer is applied on top of the metal reflector and cured with UV-light. A blank CD-R is not empty, the pregroove has a wobble, maintaining a constant rate is essential to ensure proper size and spacing of the pits and lands burned into the dye layer
17.
Optical disc drive
–
Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of media which can be read. Optical disc drives that are no longer in production include CD-ROM drive, CD writer drive, combo drive, as of 2015, DVD writer drive supporting all existing recordable and rewritable DVD formats is the most common for desktop PCs and laptops. There are also the DVD-ROM drive, BD-ROM drive, Blu-ray Disc combo drive and they are also very commonly used in computers to read software and consumer media distributed on disc, and to record discs for archival and data exchange purposes. Floppy disk drives, with capacity of 1, USB flash drives, high-capacity, small, and inexpensive, are suitable where read/write capability is required. Large backups are often made on external hard drives, as their price has dropped to a level making this viable. The first laser disc, demonstrated in 1972, was the Laservision 12-inch video disc, the video signal was stored as an analog format like a video cassette. The first digitally recorded optical disc was a 5-inch audio compact disc in a format created by Sony. The CD-ROM format was developed by Sony and Denon, introduced in 1984, as an extension of Compact Disc Digital Audio, the CD-ROM has a storage capacity of 650 MB. Also in 1984, Sony introduced a LaserDisc data storage format, in 1987, Sony demonstrated the erasable and rewritable 5. 25-inch optical drive. The first Blu-Ray prototype was unveiled by Sony in October 2000, technically Blu-ray Disc also required a thinner layer for the narrower beam and shorter wavelength blue laser. The first BD-ROM players were shipped in mid-June 2006, the first Blu-ray Disc titles were released by Sony and MGM on June 20,2006. The first mass-market Blu-ray Disc rewritable drive for the PC was the BWU-100A, initially, CD-type lasers with a wavelength of 780 nm were used. For DVDs, the wavelength was reduced to 650 nm, two main servomechanisms are used, the first to maintain the proper distance between lens and disc, to ensure the laser beam is focused as a small laser spot on the disc. The second servo moves the head along the discs radius, keeping the beam on the track. Optical disk media are read beginning at the radius to the outer edge. This is detected by photodiodes that create corresponding electrical signals, an optical disk recorder encodes data onto a recordable CD-R, DVD-R, DVD+R, or BD-R disc by selectively heating parts of an organic dye layer with a laser. This changes the reflectivity of the dye, thereby creating marks that can be read like the pits, for recordable discs, the process is permanent and the media can be written to only once
18.
Compact disc
–
Compact disc is a digital optical disc data storage format released in 1982 and co-developed by Philips and Sony. The format was developed to store and play only sound recordings but was later adapted for storage of data. The first commercially available Audio CD player, the Sony CDP-101, was released October 1982 in Japan, standard CDs have a diameter of 120 millimetres and can hold up to about 80 minutes of uncompressed audio or about 700 MiB of data. The Mini CD has various diameters ranging from 60 to 80 millimetres, they are used for CD singles, storing up to 24 minutes of audio. At the time of the introduction in 1982, a CD could store much more data than a personal computer hard drive. By 2010, hard drives commonly offered as much space as a thousand CDs. In 2004, worldwide sales of audio CDs, CD-ROMs and CD-Rs reached about 30 billion discs, by 2007,200 billion CDs had been sold worldwide. In 2014, revenues from digital music services matched those from physical format sales for the first time. American inventor James T. Russell has been credited with inventing the first system to record information on an optical transparent foil that is lit from behind by a high-power halogen lamp. Russells patent application was first filed in 1966, and he was granted a patent in 1970, following litigation, Sony and Philips licensed Russells patents in the 1980s. The compact disc is an evolution of LaserDisc technology, where a laser beam is used that enables the high information density required for high-quality digital audio signals. 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 a joint task force of engineers to design a new 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 the disc has been credited to the cooperation between Philips and Sony, who came together to agree upon and develop compatible hardware. The unified design of the disc allowed consumers to purchase any disc or player from any company. In 1974, L. However, due to the performance of the analog format
19.
Compact Disc Digital Audio
–
Compact Disc Digital Audio is the standard format for audio compact discs. The standard is defined in the Red Book, one of a series of Rainbow Books that contain the specifications for all Compact Disc formats. These parameters are common to all discs and used by all logical formats. The standard also specifies the form of audio encoding, 2-channel signed 16-bit Linear PCM sampled at 44,100 Hz. Although rarely used, the specification allows for discs to be mastered with a form of emphasis, the second edition of IEC60908 was published in 1999 and it cancels and replaces the first edition, amendment 1 and the corrigendum to amendment 1. The IEC60908 however does not contain all the information for extensions that is available in the Red Book, such as the details for CD-Text, CD+G, 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 a CD-DA consists of two-channel signed 16-bit Linear PCM sampled at 44,100 Hz, the sampling rate is adapted from that attained when recording digital audio on a PAL videotape with a PCM adaptor, an earlier way of storing digital audio. An audio CD can represent frequencies up to 22.05 kHz, the selection of the sample rate was based primarily on the need to reproduce the audible frequency range of 20–20,000 Hz. The Nyquist–Shannon sampling theorem states that a rate of more than twice the maximum frequency of the signal to be recorded is needed. The exact sampling rate of 44, the device that converts an analog audio signal into PCM audio, which in turn is changed into an analog video signal is called a PCM adaptor. This technology could store six samples in a horizontal line. 60 field/s black and white video was required, and in NTSC countries that video signal has 245 usable lines per field, similarly, PAL has 294 lines and 50 fields, which gives 44,100 samples/s/stereo channel. This system could store 14-bit samples with some correction, or 16-bit samples with almost no error correction. There was a debate over the use of 14-bit or 16-bit quantization. When the Sony/Philips task force designed the Compact Disc, Philips had already developed a 14-bit D/A converter, in the end,16 bits and 44.1 kilosamples per second prevailed. Philips found a way to produce 16-bit quality using its 14-bit DAC by using four times oversampling, some CDs are mastered with pre-emphasis, an artificial boost of high audio frequencies. The pre-emphasis improves the apparent signal-to-noise ratio by making use of the channels dynamic range
20.
CD-ROM
–
A CD-ROM /ˌsiːˌdiːˈrɒm/ is a pre-pressed optical compact disc which contains data. The name is an acronym which stands for Compact Disc Read-Only Memory, computers can read CD-ROMs, but cannot write to CD-ROMs which are not writable or erasable. From the mid-1990s until the mid-2000s, CD-ROMs were popularly used to distribute software for computers, some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer. An early CD-ROM format was developed by Sony and Denon, introduced at a Japanese computer show in 1984 and it was an extension of Compact Disc Digital Audio, and adapted the format to hold any form of digital data, with a capacity of 540 MiB. The Yellow Book is the standard that defines the format of CD-ROMs. One of a set of books that contain the technical specifications for all CD formats. CD-ROMs are identical in appearance to audio CDs, and data are stored and retrieved in a similar manner. Discs are made from a 1.2 mm thick disc of polycarbonate plastic, data is stored on the disc as a series of microscopic indentations. A laser is shone onto the surface of the disc to read the pattern of pits. This pattern of changing intensity of the beam is converted into binary data. Several formats are used for data stored on discs, known as the Rainbow Books. The Yellow Book, published in 1988, defines the specifications for CD-ROMs, the CD-ROM standard builds on top of the original Red Book CD-DA standard for CD audio. Other standards, such as the White Book for Video CDs, 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, ISO9660 defines the standard file system for a CD-ROM. ISO13490 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 ISO13346 standard was designed to address most of the shortcomings of ISO9660, and a subset of it evolved into the UDF format, which was adopted for DVDs. The bootable CD specification was issued in January 1995, to make a CD emulate a hard disk or floppy disk, is called El Torito, data stored on CD-ROMs follows the standard CD data encoding techniques described in the Red Book specification. This includes cross-interleaved Reed–Solomon coding, eight-to-fourteen modulation, and the use of pits, the structures used to group data on a CD-ROM are also derived from the Red Book
21.
Super Audio CD
–
Super Audio CD is a read-only optical disc for audio storage, introduced in 1999. It was developed jointly by Sony and Philips Electronics, and intended to be the successor to their Compact Disc format, having made little impact in the consumer audio market, by 2007, SACD was deemed to be a failure by the press. A small market for SACD has remained, serving the audiophile community, the Super Audio CD format was introduced in 1999. Royal Philips and Crest Digital partnered in May 2002 to develop and install the first SACD hybrid disc production line in the USA, SACD did not achieve the same level of growth that Compact discs enjoyed in the 1980s, and was not accepted by the mainstream market. By October 2009, record companies had published more than 6,000 SACD releases, jazz and popular music albums, mainly remastered previous releases, were the next two most numerous genres represented. Many popular artists have released some or all of their catalog on SACD. Pink Floyds album The Dark Side of the Moon sold over 800,000 copies by June 2004 in its SACD Surround Sound edition, the Whos rock opera Tommy, and Roxy Musics Avalon, were released on SACD to take advantage of the formats multi-channel capability. All three albums were remixed in 5.1 surround, and released as hybrid SACDs with a mix on the standard CD layer. Some popular artists have released new recordings on SACD, sales figures for Stings Sacred Love album reached number one on SACD sales charts in four European countries in June 2004. Between 2007 and 2008, Genesis re-released all of their studio albums across three box sets, each album in these sets contains the original album on SACD in both stereo and 5.1 mixes. The US & Canada versions do not use SACD but CD instead, by August 2009443 labels had released one or more SACDs. Instead of depending on major label support, some orchestras and artists have released SACDs on their own, many of the SACD discs that were released from 2000-2005 are now out of print and are available only on the used market. By 2009, the record companies were no longer regularly releasing discs in the format. SACD is a disc of identical physical dimensions as a compact disc. There are three types of disc, Hybrid, Hybrid SACDs are encoded with a 4.7 GB DSD layer, single-layer, A DVD-5 encoded with one 4.7 GB DSD layer. Dual-layer, A DVD-9 encoded with two DSD layers, totaling 8.5 GB, and no PCM layer, dual-layer SACDs can store nearly twice as much data as a single-layer SACD. Unlike hybrid discs, both single- and dual-layer SACDs are incompatible with conventional CD players and cannot be played on them, a stereo SACD recording has an uncompressed rate of 5.6 Mbit/s, four times the rate for Red Book CD stereo audio. Other technical parameters are as follows, Commercial releases commonly included both surround sound and stereo mixes on the SACD layer, some reissues however, retained the mixes of earlier multi-channel formats
22.
Photo CD
–
Photo CD is a system designed by Kodak for digitizing and saving photos in a CD. Launched in 1992, the discs were designed to hold nearly 100 high quality images, scanned prints, Photo CDs are defined in the Beige Book and conform to the CD-ROM XA and CD-i Bridge specifications as well. They were intended to play on CD-i players, Photo CD players, furthermore, Photo CD relied on CRT-based TV sets for home use. However, these were designed for moving pictures and their typical flicker became an issue when watching still photographs. The Photo CD system gained a level of acceptance among professional photographers due to the low cost of the high quality film scans. Prior to Photo CD, professionals who wished to digitize their film images were forced to pay higher fees to obtain drum scans of their film negatives and transparencies. The Kodak Pro Photo CD Master Disc contains 25 images with resolution of 6144 x 4096 pixels. This type is appropriate for 120 film, 4x5, but also for small picture film, separate from the Photo CD format is Kodaks proprietary Portfolio CD format, which combines Red Book CD audio and Beige Book PCD with interactive menus and hotspots on PCD images. Some standalone Philips Photo/Audio CD players could play Portfolio CDs, the Kodak Portfolio CD is not defined in any particular Rainbow Book. The Photo CD system was announced by Kodak in 1990, Photo CD targeted a full range of photographic needs, ranging from consumer level point-and-shoot cameras to high-end professionals using large format 4x5 sheet film. The first Photo CD products, including scanners for processing labs and Photo CD players for consumers, the project was expected to be a $600 million business by 1997 with $100 million in operational earnings. Kodak entered into a number of partnerships grow the usage of Photo CD and this included, for example, an arrangement with L. L. These measures, together with the relatively low cost of $3 per image and convenience. For example, a 16Base Photo CD image of 5.5 Mb can be encoded as a JPEG image of 2.1 Mb at 80% quality, when the Photo CD format was designed in the early 1990s, a design goal was to allow low cost playback-to-TV devices. While the pixel resolution of Photo CD was still comparable or better than the alternatives, firstly, the Photo CD color space, designed for TV display, is smaller than what can be achieved by even a low cost desktop scanner. Secondly, the rendition of Photo CD images changed over time. Thirdly, the range of scans was lower than for desktop scanners. Tests at the time indicated that the rating of Photo CD was 2. 8-3.0, while commonly available desktop scanners were reaching 4.2
23.
CD Video
–
CD Video is a format of optical media disc that was introduced in 1987 that combines the technologies of standard compact disc and LaserDisc. CD-V discs are the size as a standard 12-cm audio CD. It also contains up to 5 minutes of video information plus digital CD-quality sound. One of the first LaserDisc players that can play CD-V discs is the Pioneer CLD-1010 from 1987, though it is a CD-based format, CD Video was never given a rainbow book designation. CD Video discs have a gold color, to differentiate them from regular silver-colored audio CDs. This is a characteristic that would later be replicated in HVD, a similar version of CD Video called Video Single Disc was also released. It is basically the same as CD Video, but it only has the video track. CD Video was targeted toward teenagers who watched music videos on MTV, however, few of them were familiar with LaserDiscs, and far fewer owned CDV-compatible players at the time. Buying a costly new player was not an option just for the use of playing a single music video that can be recorded with a VCR. IEC61104 - Compact disc video system -12 cm CD-V A webpage on CD Video discs, featuring a list of NTSC CD-V releases The LaserDisc Database, including CD Video
24.
Video CD
–
Video CD is a home video format and the first format for distributing films on standard 120 mm optical discs. The format was adopted in Southeast Asia instead of VHS. The format is a digital format for storing video on a compact disc. VCDs are playable in dedicated VCD players, most DVD and Blu-ray Disc players, personal computers, the Video CD standard was created in 1993 by Sony, Philips, Matsushita, and JVC and is referred to as the White Book standard. Although they have been superseded by other media, VCDs continue to be retailed as a low-cost video format, in 1979, Philips introduced the optical LaserDisc, which was about 30 cm in diameter. This disc could hold an hour of analog video along with audio on each side. The Laserdisc provided picture quality nearly double that of VHS tape, Philips later teamed up with Sony to develop a new type of disc, the compact disc or CD. Introduced in 1982 in Japan, the CD is about 120 mm in diameter, the format was initially designed to store digitized sound and proved to be a success in the music industry. A few years later, Philips decided to give CDs the ability to produce video and this led to the creation of CD Video in 1987. However, the small size significantly impeded the ability to store analog video. Therefore, CD-V distribution was limited to featuring music videos, by the early 1990s engineers were able to digitize and compress video signals, greatly improving storage efficiency. Because this new format could hold 83 minutes of audio and video, extra capacity was obtained by sacrificing the error correction. This format was named Video CD or VCD, VCD enjoyed a brief period of success, with a few major feature films being released in the format. However, VCDs are still being released in countries in Asia. The development of sophisticated, higher capacity optical disc formats yielded the DVD format. DVD players use lasers that are of shorter wavelength than those used on CDs, allowing the recorded pits to be smaller, the DVD was so successful that it eventually pushed VHS out of the video market once suitable recorders became widely available. Nevertheless, VCDs made considerable inroads into developing nations, where they are still in use today, Video CDs comply with the CD-i Bridge format, and are authored using tracks in CD-ROM XA mode. The first track of a VCD is in CD-ROM XA Mode 2 Form 1 and this track may also contain other non-essential files, and is shown by operating systems when loading the disc
25.
Super Video CD
–
Super Video CD is a digital format for storing video on standard compact discs. SVCD was intended as a successor to Video CD and an alternative to DVD-Video, although SVCDs proved more sophisticated than VCDs, the format remains in the latters shadow. Similar to VCDs, SVCDs comply with the CD-i Bridge format, the first track is in CD-ROM XA Mode 2, Form 1, and contains metadata about the disc. The other tracks are in Mode 2, Form 2, and contain audio and this allows roughly 800 megabytes of data to be stored on one 80 minute CD. One CD can hold up to 35 minutes of full quality SVCD-format video, on the downside, this increase in picture resolution sacrifices video length capacity by over 50%. Because of this, titles released on SVCD has to come in twice the number of discs of their VCD equivalents. Unlike other CD-based formats, such as China Video Disc and Video CD, however, many DVD and Blu-ray players will play back SVCD resolution video from a DVD or Blu-ray disc anyway. Interlaced video is supported for SVCD video, though not required,23.976 frames per second video is supported by use of interlacing and 3,2 pulldown. The combined audio and video bit rates should not exceed 2.7 Mbps and this data rate was chosen, in part, to ensure compatibility with slower and less expensive 2 × speed CD drives. Codec, MPEG-1 Audio Layer II Frequency,44,100 hertz Output, Monaural, dual channel, stereo, SVCDs may have two separate stereo, or four mono audio tracks. Audio may have up to 6 channels using the MPEG Multichannel surround sound format, although space constraints and inconsistent hardware support make it impractical, variable bit rate encoding, while not supported by the MPEG-1 Audio Layer II standard, is part of the SVCD specification. However, variable bit rate audio is not consistently supported by standalone players, play back of SVCD titles is impaired when played on most DVD players, causing dropped frames, choppy video playback or skipping of sound. This is due to the unfortunately chosen two-thirds video ratio in the SVCD format specifications, most DVD players support the video formats VCD, SVCD and DVD but the best resolution usually dictates the design of all the electronics components, most notably the low pass filter. With only one analog low pass filter optimised for one video format, the SVCD format is especially prone to foldover because the 480p format doesnt fit well over a 720p output. Although the aliasing artifacts that result from this bad fit are usually buried in noise from other sources, such as camera, quantization, China Video Disc is a CD-based video format which was created during the development of the SVCD standard and is almost identical to SVCD. The primary technical difference is a video resolution of 352×480 or 352×576. Because 352×480/576 is a recognized DVD resolution, CVD video is fully compatible with the DVD-Video standard, the lower resolution also allows the bitrate to be reduced while keeping compression artifacts to a minimum. CVD also supports all of the features which are supported by SVCD
26.
CD+G
–
CD+G is an extension of the compact disc standard that can present low-resolution graphics alongside the audio data on the disc when played on a compatible device. CD+G discs are used for karaoke machines, which use this functionality to present on-screen lyrics for the song contained on the disc. The CD+G specifications were published by Philips and Sony in a revision of the Red Book specifications. The first CD to be released with CD+G graphics was Eat or Be Eaten by Firesign Theatre in 1985, the CD+EG is a similar format that allows for better graphics, but has been used very rarely. Some CD-ROM drives can read this data. Pioneers LaserActive player can also play CD+G discs, as long as either the PAC-S1/S-10 or PAC-N1/N10 game modules are installed, since 2003, some standalone DVD players have supported the CD+G format. The CD+G format takes advantage of the subcode channels R through W and these six bits store graphics information. In the CD+G system, 16-color graphics are displayed on a field which is 300×216 pixels in size. Compact disc Karaoke MP3+G The CD+G Museum and Discography, details on released titles and how to identify them CD+G faq
27.
CD-Text
–
CD-Text is an extension of the Red Book Compact Disc specifications standard for audio CDs. It allows for storage of information on a standards-compliant audio CD. The specification for CD-Text was included in the Multi-Media Commands Set 3 R01 standard, released in September 1996 and it was also added to new revisions of the Red Book. The actual text is stored in a compatible with Interactive Text Transmission System. The ITTS standard is applied in the MiniDisc format, as well as in Digital Audio Broadcasting technology. The CD-Text information is stored in the subchannels R to W on the disc and this information is usually stored in the subchannels in the lead-in area of the disc, where there is roughly five kilobytes of space available. It can also be stored on the program area of the disc. Since the R to W channels are not used in the Red Book specification of audio CDs, they are not read by all CD players, of these, three are reserved and therefore they dont have keywords. The character encoding is not specified, and there is no provision for indicating in the CD-Text data which encoding is in use, the original Sony authoring tools and specifications supported ASCII and two of its supersets, ISO-8859-1 and MS-JIS. Annex J of the MMC-2 specification mentions only ASCII, but provides for double byte character codes to be indicated, cdrdao, Linux command line tool that supports writing CD-Text. CDRWIN can burn CD-Text Exact Audio Copy has support for reading CD-Text to fill in artist/title information when ripping CDs, foobar2000 Since version 1.0 has support for reading CD-Text to fill in artist/title information when playing and ripping CDs. Fre, ac has support for reading CD-Text to fill in artist/title information when ripping CDs, icedax, Linux command line tool that supports reading CD-Text. This information can be added/modified during the creation of a. CUE file, isoBuster copies CD-Text when a CD is ripped in raw format and saves it to a. cdt file. ITunes 7 or higher supports burning CD Text and it is by default an unchecked option in the burning preferences. K3b has support for reading and writing CD-Text on Linux, Media Player Classic reads from CD-Text and will automatically display track title and author. MusicBee audio player/organizer can read CD-Text when playing or ripping CDs, nero Burning ROM can burn CD-Text since version 5.5.10, its track saving utility can read CD-Text when ripping. RealPlayer 10 supports reading and writing of CD-Text Sound Juicer can read from CD-Text Toast on Mac OS X has support for CD-Text, VLC media player can read CD-Text on all platforms Winamp has had support for reading CD-Text since version 5.31, but does not write CD-Text. Windows Media Player 10 and higher with the WMPCDText plug-in supports reading CD-Text, x-CD-Roast for Linux has had reading/writing support since version 0. 98alpha10
28.
Green Book (CD standard)
–
The standard was originally not freely available and had to be licensed from Philips. However, the 1994 version of the standard was made available for free by Philips. CD-i discs conform to the Red Book specification of audio CDs, tracks on a CD-is program area can be CD-DA tracks or CD-i tracks, but the first track must always be a CD-i track, and all CD-i tracks must be grouped together at the beginning of the area. CD-i tracks are structured according to the CD-ROM XA specification, and have different classes depending on their contents, message sectors contain audio data to warn users of CD players that the track they are trying to listen to is a CD-i track and not a CD-DA track. The CD-i specification also specifies a system similar to ISO9660 to be used on CD-i tracks. The CD-i Ready format is a type of format, also designed by Philips. This format puts CD-i software and data into the pregap of Track 1, the CD-i Bridge format, defined in Philips White Book, is a transitional format allowing bridge discs to be played both on CD-ROM drives and on CD-i players
29.
DVD recordable
–
DVD recordable and DVD rewritable refer to part of optical disc recording technologies. DVD recordable is a term that refers to both write-once and rewritable formats, whereas DVD rewritable refers only to rewritable formats. Like CD-Rs, DVD recordables use dyes, depending on the intensity of the laser, the reflective property of the dye on a particular spot will determine whether it is a peak or a valley representation from pressed DVD. Dyes give the side of a disc a distinct color. Dyes are also the playback is not guaranteed. Their reflective properties are not as good as with stamped DVDs that commonly have aluminum as the reflective layer, the larger storage capacity of a DVD-R compared to a CD-R is achieved through smaller pit size and smaller track pitch of the groove spiral which guides the laser beam. Consequently, more pits can be written on the same physical sized disc, in order to write smaller pits onto the recording dye layer, a red laser beam with a wavelength of 640 nm is used in conjunction with a higher numerical aperture lens. Because of this wavelength, DVDs use different dyes from CDs to properly absorb this wavelength. The R format DVDs can be once and read arbitrarily many times. Thus, R format discs are suited to such as non-volatile data storage, audio. This can cause confusion because the DVD+RW Alliance logo is a stylized RW, thus, a DVD+R disc may have the RW logo, but it is not rewritable. According to Pioneer, DVD-RW discs may be written to about 1,000 times before needing replacement, RW discs are commonly used to store data in a volatile format, such as when creating backups or collections of files. They are also used for home DVD video recorders, one benefit to using a rewritable disc is, if there are writing errors when recording data, the disc is not ruined and can still store data by erasing the faulty data. The DVD-R format was developed by Pioneer in 1997 and it is supported by most normal DVD players and is approved by the DVD Forum. Has broader playback compatibility than the + especially with older players. The dash format uses a land pre-pit method to provide sector address information, DVD minus R is not correct, according to DVD-R consortium recommendations, it is, in fact, a dash. DVD-R and DVD+R technologies are not directly compatible, which created a war in the DVD technology industry. To reconcile the two competing formats, manufacturers created hybrid drives that could read both — most hybrid drives that handle both formats are labeled DVD±R and Super Multi and are very popular, developed by Philips and Sony with their DVD+RW Alliance
30.
DVD+R DL
–
DVD+R DL also called DVD+R9, is a derivative of the DVD+R format created by the DVD+RW Alliance. Its use was first demonstrated in October 2003, DVD+R DL discs employ two recordable dye layers, each capable of storing nearly the 4.7 GB capacity of a single-layer disc, almost doubling the total disc capacity to 8.5 GB. Discs can be read in many DVD devices and can only be created using DVD+R DL, DL drives started appearing on the market during mid-2004, at prices comparable to those of existing single-layer drives. As of March 2011 DL media is up to twice as expensive as single-layer media, the latest DL drives write double layer discs at a slower rate than current single-layer discs. Dual-layer recording allows DVD-R and DVD+R discs to store more data, up to 8.5 gigabytes per disc. DVD-R DL was developed for the DVD Forum by Pioneer Corporation, while DVD+R DL was developed for the DVD+RW Alliance by Philips, a dual-layer disc differs from its usual DVD counterpart by employing a second physical layer within the disc itself. The drive with dual-layer capability accesses the second layer by shining the laser through the first semi-transparent layer, the layer change can exhibit a noticeable pause in some DVD players, up to several seconds. DVD recordable discs supporting this technology are compatible with some existing DVD players. Many current DVD recorders support dual-layer technology, and the price is now comparable to that of single-layer drives, the recording speeds reached by dual-layer media are still well below those of single-layer media. There are two modes for dual-layer orientation, parallel track path and opposite track path, in PTP mode, used for DVD-ROM, both layers start recording at the inside diameter with the lead-in and end at the outside diameter with the lead-out. Sectors are sequenced from the beginning of the first layer to the end of the first layer, in OTP mode, the second layer is read from the outside of the disk. For DVD-Video a variation of the technique is employed and this means that the start of the second layer may not have any recorded material present. This is in order to minimise the time that the player takes to locate and focus on the second layer. A common misconception is that the disc spins first in one direction, and then another, either for PTP or OTP recording, when in fact DVD-Writers always spin a disc in the clockwise direction. A simpler way to understand whats written above is to think of the hole in the centre of the DVD as the inside. This results in the skipping or freezing up for some time as the laser head repositions itself. For comparison, the table below shows storage capacities of the four most common DVD recordable media, stands for standard single-layer discs, while DL denotes the dual-layer variants. See articles on the formats in question for information on compatibility issues, DVD-R DL DVD DVD+R DVD+RW DVD+RW DL Book type MultiLevel Recording Bennett, Hugh
