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Disk Pack
Disk packs and disk cartridges were early forms of removable media for computer data storage, introduced in the 1960s.Contents1 Disk pack 2 Disk cartridge 3 Alignment 4 References 5 See alsoDisk pack[edit] Disk pack
Disk pack
manufactured by Nashua, USA, without its protective cover. A 3.5" modern hard drive is shown for comparison.A Disk pack
Disk pack
is a layered grouping of hard disk platters (circular, rigid discs coated with a magnetic data storage surface). A disk pack is the core component of a hard disk drive. In modern hard disks, the disk pack is permanently sealed inside the drive. In many early hard disks, the disk pack was a removable unit, and would be supplied with a protective canister featuring a lifting handle. The protective cover consisted of two parts, a clear plastic shell, with a handle in the center, that enclosed the top and sides of the disks and a separate bottom that completed the sealed package
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Computer Storage Density
Areal density is a measure of the quantity of information bits that can be stored on a given length of track, area of surface, or in a given volume of a computer storage medium. Generally, higher density is more desirable, for it allows greater volumes of data to be stored in the same physical space. Density therefore has a direct relationship to storage capacity of a given medium. Density also generally has a fairly direct effect on the performance within a particular medium, as well as price.Contents1 Storage device classes1.1 Magnetic disk media 1.2 Optical disc media 1.3 Magnetic tape media2 Research 3 Effects on performance 4 Effects on price 5 See also 6 ReferencesStorage device classes[edit] Magnetic disk media[edit] Hard disk
Hard disk
drives store data in the magnetic polarization of small patches of the surface coating on a disk
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Compact Disc
Compact disc
Compact disc
(CD) is a digital optical disc data storage format that was co-developed by Philips
Philips
and Sony
Sony
and released in 1982. The format was originally developed to store and play only sound recordings but was later adapted for storage of data (CD-ROM). Several other formats were further derived from these, including write-once audio and data storage (CD-R), rewritable media (CD-RW), Video Compact Disc (VCD), Super Video Compact Disc (SVCD), Photo CD, PictureCD, CD-i, and Enhanced Music CD. The first commercially available Audio CD player, the Sony
Sony
CDP-101, was released October 1982 in Japan. Standard CDs have a diameter of 120 millimetres (4.7 in) and can hold up to about 80 minutes of uncompressed audio or about 700  MiB of data
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Computer Data Storage
Computer
Computer
data storage, often called storage or memory, is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.[1]:15–16 The central processing unit (CPU) of a computer is what manipulates data by performing computations. In practice, almost all computers use a storage hierarchy,[1]:468–473 which puts fast but expensive and small storage options close to the CPU
CPU
and slower but larger and cheaper options farther away. Generally the fast volatile technologies (which lose data when off power) are referred to as "memory", while slower persistent technologies are referred to as "storage". In the Von Neumann architecture, the CPU
CPU
consists of two main parts: The control unit and the arithmetic logic unit (ALU)
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Hard Disk Platter
A hard disk drive platter (or disk) is the circular disk on which magnetic data is stored in a hard disk drive. The rigid nature of the platters in a hard drive is what gives them their name (as opposed to the flexible materials which are used to make floppy disks). Hard drives typically have several platters which are mounted on the same spindle. A platter can store information on both sides, requiring two heads per platter.Contents1 Design 2 Manufacture 3 See also 4 ReferencesDesign[edit] The magnetic surface of each platter is divided into small sub-micrometer-sized magnetic regions, each of which is used to represent a single binary unit of information
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Magnetic
Magnetism
Magnetism
is a class of physical phenomena that are mediated by magnetic fields. Electric currents and the magnetic moments of elementary particles give rise to a magnetic field, which acts on other currents and magnetic moments. The most familiar effects occur in ferromagnetic materials, which are strongly attracted by magnetic fields and can be magnetized to become permanent magnets, producing magnetic fields themselves. Only a few substances are ferromagnetic; the most common ones are iron, nickel and cobalt and their alloys. The prefix ferro- refers to iron, because permanent magnetism was first observed in lodestone, a form of natural iron ore called magnetite, Fe3O4. Although ferromagnetism is responsible for most of the effects of magnetism encountered in everyday life, all other materials are influenced to some extent by a magnetic field, by several other types of magnetism
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Data Storage Device
Data
Data
storage is the recording (storing) of information (data) in a storage medium. Recording is accomplished by virtually any form of energy. DNA
DNA
and RNA, handwriting, phonographic recording, magnetic tape, and optical discs are all examples of storage media. Electronic data storage requires electrical power to store and retrieve data. Data
Data
storage in a digital, machine-readable medium is sometimes called digital data. Computer data storage
Computer data storage
is one of the core functions of a general purpose computer
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History Of Hard Disk Drives
In 1953, IBM
IBM
recognized the immediate application for what it termed a "Random Access File" having high capacity and rapid random access at a relatively low cost.[1] After considering technologies such as wire matrices, rod arrays, drums, drum arrays, etc.,[1] the engineers at IBM's San Jose California laboratory invented the hard disk drive.[2] The disk drive created a new level in the computer data hierarchy, then termed Random Access Storage but today known as secondary storage, less expensive and slower than main memory (then typically drums) but faster and more expensive than tape drives.[3] The commercial usage of hard di
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De Facto Standard
A de facto standard is a custom or convention that has achieved a dominant position by public acceptance or market forces (for example, by early entrance to the market). De facto is a Latin phrase that means in fact (literally by or from fact) in the sense of "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established", as opposed to de jure. The term de facto standard is used in contrast with obligatory standards (also known as "de jure standards"); or to express the dominant voluntary standard, when there is more than one standard available for the same use. In social sciences, a voluntary standard that is also a de facto standard is a typical solution to a coordination problem.[1] The choice of a de facto standard tends to be stable in situations in which all parties can realize mutual gains, but only by making mutually consistent decisions
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Optical Disc
In computing and optical disc recording technologies, an optical disc (OD) is a flat, usually circular disc which encodes binary data (bits) in the form of pits (binary value of 0 or off, due to lack of reflection when read) and lands (binary value of 1 or on, due to a reflection when read) on a special material (often aluminium[1] ) on one of its flat surfaces. The encoding material sits atop a thicker substrate (usually polycarbonate) which makes up the bulk of the disc and forms a dust defocusing layer. The encoding pattern follows a continuous, spiral path covering the entire disc surface and extending from the innermost track to the outermost track
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IBM 1130
The IBM
IBM
1130 Computing System, introduced in 1965,[1] was IBM's least expensive computer at that time
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Digital Equipment Corporation
Digital Equipment Corporation, also known as DEC and using the trademark Digital, was a major American company in the computer industry from the 1950s to the 1990s. DEC was a leading vendor of computer systems, including computers, software, and peripherals. Their PDP and successor VAX
VAX
products were the most successful of all minicomputers in terms of sales. DEC was acquired in June 1998 by Compaq, in what was at that time the largest merger in the history of the computer industry. At the time, Compaq
Compaq
was focused on the enterprise market and had recently purchased several other large vendors. DEC was a major player overseas where Compaq
Compaq
had less presence. However, Compaq
Compaq
had little idea what to do with its acquisitions, and soon found itself in financial difficulty of its own
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Blu-Ray
Blu-ray
Blu-ray
or Blu-ray
Blu-ray
Disc (BD) is a digital optical disc data storage format. It was designed to supersede the DVD
DVD
format, and is capable of storing several hours of video in high-definition (HDTV 720p and 1080p) and ultra high-definition resolution (2160p). The main application of Blu-ray
Blu-ray
is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4
PlayStation 4
and Xbox One
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Peripheral Device
A peripheral device is "an ancillary device used to put information into and get information out of the computer."[1] Three categories of peripheral devices exist based on their relationship with the computer:an input device sends data or instructions to the computer, such as a mouse, keyboard, graphics tablet, image scanner, barcode reader, game controller, light pen, light gun, microphone, digital camera, webcam, dance pad, and read-only memory); an output device provides output from the computer, such as a computer monitor, projector, printer, and computer speaker); and an input/output device performs both input and output functions, such as a computer data storage device (including a disk drive, USB flash drive, memory card, and tape drive) and a touchscreen).Many modern electronic devices, such as digital watches, smartphones, and tablet computers, have interfaces that allow them to be used as computer peripheral devices. See also[edit]Look up peripheral in Wi
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Disk Read-and-write Head
Disk read/write heads are the small parts of a disk drive which move above the disk platter and transform the platter's magnetic field into electrical current (read the disk) or, vice versa, transform electrical current into magnetic field (write the disk).[1] The heads have gone through a number of changes over the years.Contents1 Description1.1 Traditional head 1.2 Metal
Metal
in Gap (MIG) 1.3 Magnetoresistance 1.4 Tunneling magnetoresistance (TMR) 1.5 Perpendicular magnetic recording
Perpendicular magnetic recording
(PMR)2 References 3 External linksDescription[edit] In a hard drive, the heads 'fly' above the disk surface with clearance of as little as 3 nanometres. The "flying height" is constantly decreasing to enable higher areal density. The flying height of the head is controlled by the design of an air-bearing etched onto the disk-facing surface of the slider
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DVD
DVD
DVD
(an abbreviation of "digital video disc"[5] or "digital versatile disc"[6][7]) is a digital optical disc storage format invented and developed by Philips
Philips
and Sony
Sony
in 1995. The medium can store any kind of digital data and is widely used for software and other computer files as well as video programs watched using DVD
DVD
players. DVDs offer higher storage capacity than compact discs while having the same dimensions. Prerecorded 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
DVD
discs ( DVD-R
DVD-R
and DVD+R) can be recorded once using a DVD recorder and then function as a DVD-ROM
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