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Magnetic Tape Data Storage
Magnetic-tape data storage is a system for storing digital information on magnetic tape using digital recording. Tape was an important medium for primary data storage in early computers, typically using large open reels of 7-track, later 9-track tape. Modern magnetic tape is most commonly packaged in cartridges and cassettes, such as the widely supported Linear Tape-Open (LTO) and IBM 3592 series. The device that performs the writing or reading of data is called a tape drive. Autoloaders and tape libraries are often used to automate cartridge handling and exchange. Compatibility was important to enable transferring data. Tape data storage is now used more for system backup, data archive and data exchange. The low cost of tape has kept it viable for long-term storage and archive. Open reels Initially, magnetic tape for data storage was wound on reels. This standard for large computer systems persisted through the late 1980s, with steadily increasing capacity d ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Information
Digital data, in information theory and information systems, is information represented as a string of Discrete mathematics, discrete symbols, each of which can take on one of only a finite number of values from some alphabet (formal languages), alphabet, such as letters or digits. An example is a text document, which consists of a string of alphanumeric characters. The most common form of digital data in modern information systems is ''binary data'', which is represented by a string of binary digits (bits) each of which can have one of two values, either 0 or 1. Digital data can be contrasted with ''analog data'', which is represented by a value from a continuous variable, continuous range of real numbers. Analog data is transmitted by an analog signal, which not only takes on continuous values but can vary continuously with time, a continuous real-valued function of time. An example is the air pressure variation in a sound wave. The word ''digital'' comes from the same sour ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phosphor Bronze
A phosphor is a substance that exhibits the optical phenomenon, phenomenon of luminescence; it emits light when exposed to some type of radiant energy. The term is used both for fluorescence, fluorescent or phosphorescence, phosphorescent substances which glow on exposure to ultraviolet or visible light, and cathodoluminescence, cathodoluminescent substances which glow when struck by an electron beam (cathode rays) in a cathode-ray tube. When a phosphor is exposed to radiation, the orbital electrons in its molecules are excited to a higher energy level; when they return to their former level they emit the energy as light of a certain color. Phosphors can be classified into two categories: fluorescent substances which emit the energy immediately and stop glowing when the exciting radiation is turned off, and Phosphorescence, phosphorescent substances which emit the energy after a delay, so they keep glowing after the radiation is turned off, decaying in brightness over a peri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vacuum Column (tape Drive)
9-track tape is a format for magnetic-tape data storage, introduced with the IBM System/360 in 1964. The wide magnetic tape media and reels have the same size as the earlier IBM 7-track format it replaced, but the new format has eight data tracks and one parity track for a total of nine parallel tracks. Data is stored as 8-bit characters, spanning the full width of the tape (including the parity bit). Various recording methods have been employed during its lifetime as tape speed and data density increased, including PE ( phase encoding), GCR ( group-coded recording), and NRZI (non-return-to-zero, inverted, sometimes pronounced "nur-zee"). Tapes come in various sizes up to in length. The standard size of a byte was effectively set at eight bits with the S/360 and nine-track tape. For over 30 years the format dominated offline storage and data transfer, but by the end of the 20th century it was obsolete, and the last manufacturer of tapes ceased production in early 2002, with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 729
The IBM 729 Magnetic Tape Unit was IBM's tape mass storage system from the late 1950s through the mid-1960s. Part of the IBM 7-track family of tape units, it was used on late 700, most 7000 and many 1400 series computers. Like its predecessor, the IBM 727 and many successors, the 729 used magnetic tape up to long wound on reels up to diameter. To allow rapid tape acceleration (and thus reduced seek/access times), long vacuum columns were placed between the tape reels and the read/write heads to absorb sudden increases in tape tension which would otherwise break the tape. Write protection was provided by a removable plastic ring in the back of the tape reel. Data format The tape had seven parallel tracks, six for data and one to maintain parity. Tapes with character data (BCD) were recorded in even parity. Binary tapes used odd parity (709 manual, p. 20). Aluminum strips were glued several feet from the ends of the tape to serve as physical beginning and end of tap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 727
The IBM 727 Magnetic Tape Unit was announced for the IBM 701 and IBM 702 on September 25, 1953. It became IBM's standard tape drive for their early vacuum-tube era computer systems. Later vacuum-tube machines and first-generation transistor computers used the IBM 729-series tape drive. The 727 was withdrawn on May 12, 1971. Overview The tape had seven parallel tracks – six for data and one to maintain parity. Tapes with character data ( BCD) were recorded in even parity. Binary tapes used odd parity. Reflective strips were glued several feet from the ends of the tape to serve as physical beginning and end of tape markers. Write protection is provided by a removable plastic ring in the back of the tape reel. Installing the ring enables writing, thus strictly speaking, it is a write enable ring, and removing it protects the tape from being written to. Gallery Image:IBM_704_mainframe.gif, An IBM 704 mainframe with IBM 727 tape drives on the left. (image courtesy of LLNL ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
CDC 6000 Series
The CDC 6000 series is a discontinued family of mainframe computers manufactured by Control Data Corporation in the 1960s. It consisted of the CDC 6200, CDC 6300, #Versions, CDC 6400, #Versions, CDC 6500, CDC 6600 and #Versions, CDC 6700 computers, which were all extremely rapid and efficient for their time. Each is a large, Solid-state electronics, solid-state, general-purpose, digital computer that performs scientific and business data processing as well as multiprogramming, multiprocessing, Remote Job Entry, time-sharing, and data management tasks under the control of the operating system called CDC SCOPE, SCOPE (Supervisory Control Of Program Execution). By 1970 there also was a time-sharing oriented operating system named KRONOS. They were part of the first generation of supercomputers. The 6600 was the flagship of Control Data's 6000 series. Overview The CDC 6000 series computers are composed of four main functional devices: * the central memory * one or two high-speed cen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Control Data Corporation
Control Data Corporation (CDC) was a mainframe and supercomputer company that in the 1960s was one of the nine major U.S. computer companies, which group included IBM, the Burroughs Corporation, and the Digital Equipment Corporation (DEC), the NCR Corporation (NCR), General Electric, Honeywell, RCA, and UNIVAC. For most of the 1960s, the strength of CDC was the work of the electrical engineer Seymour Cray who developed a series of fast computers, then considered the fastest computing machines in the world; in the 1970s, Cray left the Control Data Corporation and founded Cray Research (CRI) to design and make supercomputers. In 1988, after much financial loss, the Control Data Corporation began withdrawing from making computers and sold the affiliated companies of CDC; in 1992, CDC established Control Data Systems, Inc. The remaining affiliate companies of CDC currently do business as the software company Dayforce. Background: World War II – 1957 During World War II the Un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PET Film (biaxially Oriented)
BoPET (biaxially oriented polyethylene terephthalate) is a polyester film made from stretched polyethylene terephthalate (PET) and is used for its high tensile strength, chemical stability, dimensional stability (fabric), dimensional stability, Transparency (optics), transparency reflectivity, and electrical insulation. When Metallised film, metallized, it has gas and moisture barrier properties. The film is "biaxially oriented", which means that the polymer chains are oriented parallel to the plane of the film, and therefore oriented over two axes. A variety of companies manufacture boPET and other polyester films under different brand names. In the UK and US, the best-known trade names are Mylar, Melinex, Lumirror and Hostaphan. It was the first biaxially oriented polymer to be manufactured on a mass commercial scale. History BoPET film was developed in the mid-1950s,Izard, Emmette Farr"Production of polyethylene terephthalate" U.S. patent no. 2,534,028 (filed: 1948 May 13; i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thousandth Of An Inch
A thousandth of an inch is a derived unit of length in a system of units using inches. Equal to of an inch, a thousandth is commonly called a thou (used for both singular and plural) or, particularly in North America, a mil (plural mils). The words are shortened forms of the English and Latin words for "thousand" ( in Latin). In international engineering contexts, confusion can arise because ''mil'' is a formal unit name in North America but ''mil'' or ''mill'' is also a common colloquial clipped form of millimetre. The units are considerably different: a millimetre is approximately 39 mils. Contexts of use The thou, or mil, is most commonly used in engineering and manufacturing in non-metric countries. For example, in specifying: * The thickness of items such as paper, film, foil, wires, paint coatings, latex gloves, plastic sheeting, and fibers ** For example, most plastic ID cards are about in thickness. ** Card stock thickness in the United States, where mils are also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
De Facto Standard
A ''de facto'' standard is a custom or convention that is commonly used even though its use is not required. is a Latin phrase (literally " of fact"), here meaning "in practice but not necessarily ordained by law" or "in practice or actuality, but not officially established". A ''de facto'' standard contrasts an international standard which is defined by an organization such as International Standards Organization, or a standard required by law (also known as ''de jure'' standards). Joint technical committee on information technology (ISO/IEC JTC1) developed a procedure in order for de facto standards to be processed through the formal standardization system to be transformed into international standards from ISO and IEC. In social sciences a voluntary standard that is also a ''de facto'' standard is a typical solution to a coordination problem. The choice of a ''de facto'' standard tends to be stable in situations in which all parties can realize mutual gains, but only by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron(III) Oxide
Iron(III) oxide or ferric oxide is the inorganic compound with the formula . It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when used in pigments. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (), which also occurs naturally as the mineral magnetite. Iron(III) oxide is often called rust, since rust shares several properties and has a similar composition; however, in chemistry, rust is considered an ill-defined material, described as hydrous ferric oxide. Ferric oxide is readily attacked by even weak acids. It is a weak oxidising agent, most famously when reduced by aluminium in the thermite reaction. Structure can be obtained in various polymorphs. In the primary polymorph, α, iron adopts octahedral coordination geometry. That is, each Fe center is bound to six oxygen ligands. In t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
IBM 700/7000 Series
The IBM 700/7000 series is a series of large-scale (Mainframe computer, mainframe) computer systems that were made by IBM through the 1950s and early 1960s. The series includes several different, incompatible processor architectures. The 700s use vacuum-tube logic and were made obsolete by the introduction of the transistor computer, transistorized 7000s. The 7000s, in turn, were eventually replaced with IBM System/360, System/360, which was announced in 1964. However the 360/65, the first 360 powerful enough to replace 7000s, did not become available until November 1965. Early problems with OS/360 and the high cost of converting software kept many 7000s in service for years afterward. Architectures The IBM 700/7000 series has six completely different ways of storing data and instructions: *First scientific (36/18-bit words): IBM 701, 701 (Defense Calculator) *Later scientific (36-bit words, hardware Floating-point arithmetic, floating-point): IBM 704, 704, IBM 709, 709, IBM 70 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
