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DRAM
Dynamic random-access memory
Dynamic random-access memory
(DRAM) is a type of random access semiconductor memory that stores each bit of data in a separate tiny capacitor within an integrated circuit. The capacitor can either be charged or discharged; these two states are taken to represent the two values of a bit, conventionally called 0 and 1. The electric charge on the capacitors slowly leaks off, so without intervention the data on the chip would soon be lost. To prevent this, DRAM requires an external memory refresh circuit which periodically rewrites the data in the capacitors, restoring them to their original charge. Because of this refresh requirement, it is a dynamic memory as opposed to static random-access memory (SRAM) which does not require data to be refreshed. Unlike flash memory, DRAM is volatile memory (vs. non-volatile memory), since it loses its data quickly when power is removed
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Hard Disk Drive
A hard disk drive (HDD), hard disk, hard drive or fixed disk[b] is a data storage device that uses magnetic storage to store and retrieve digital information using one or more rigid rapidly rotating disks (platters) coated with magnetic material. The platters are paired with magnetic heads, usually arranged on a moving actuator arm, which read and write data to the platter surfaces.[2] Data is accessed in a random-access manner, meaning that individual blocks of data can be stored or retrieved in any order and not only sequentially. HDDs are a type of non-volatile storage, retaining stored data even when powered off.[3][4][5] Introduced by IBM
IBM
in 1956,[6] HDDs became the dominant secondary storage device for general-purpose computers by the early 1960s. Continuously improved, HDDs have maintained this position into the modern era of servers and personal computers
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Dekatron
In electronics, a Dekatron
Dekatron
(or Decatron, or generically three-phase gas counting tube or glow-transfer counting tube or cold cathode tube) is a gas-filled decade counting tube. Dekatrons were used in computers, calculators and other counting-related products during the 1950s and 1960s. "Dekatron," now a generic trademark, was the brand name used by Ericsson Telephones Limited (ETL), of Beeston, Nottingham (not to be confused with the Swedish TelefonAB Ericsson
Ericsson
of Stockholm).A dekatron in operation.The dekatron was useful for computing, calculating and frequency-dividing purposes because one complete revolution of the neon dot in a dekatron means 10 pulses on the guide electrode(s), and a signal can be derived from one of the ten cathodes in a dekatron to send a pulse, possibly for another counting stage
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Core Rope Memory
Core rope memory
Core rope memory
is a form of read-only memory (ROM) for computers, first used in the 1960s by early NASA Mars space probes and then in the Apollo Guidance Computer
Computer
(AGC) designed and programmed by the Massachusetts Institute of Technology
Massachusetts Institute of Technology
(MIT) Instrumentation Lab and built by Raytheon. Contrary to ordinary coincident-current magnetic-core memory, which was used for random access memory (RAM) at the time, the ferrite cores in a core rope are just used as transformers. The signal from a word line wire passing through a given core is coupled to the bit line wire and interpreted as a binary "one", while a word line wire that bypasses the core is not coupled to the bit line wire and is read as a "zero"
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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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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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Magnetic Tape
Magnetic tape
Magnetic tape
is a medium for magnetic recording, made of a thin, magnetizable coating on a long, narrow strip of plastic film. It was developed in Germany
Germany
in 1928, based on magnetic wire recording. Devices that record and play back audio and video using magnetic tape are tape recorders and video tape recorders. A device that stores computer data on magnetic tape is known as a tape drive. Magnetic tape
Magnetic tape
revolutionized broadcast and recording. It allowed radio, which had always been broadcast live, to be recorded for later or repeated airing. It allowed gramophone records to be recorded in multiple parts, which were then mixed and edited with tolerable loss in quality
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Die (integrated Circuit)
A die (pronunciation: /dʌɪ/) in the context of integrated circuits is a small block of semiconducting material, on which a given functional circuit is fabricated. Typically, integrated circuits are produced in large batches on a single wafer of electronic-grade silicon (EGS) or other semiconductor (such as GaAs) through processes such as photolithography. The wafer is cut (“diced”) into many pieces, each containing one copy of the circuit
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Integrated Circuit
An integrated circuit or monolithic integrated circuit (also referred to as an IC, a chip, or a microchip) is a set of electronic circuits on one small flat piece (or "chip") of semiconductor material, normally silicon. The integration of large numbers of tiny transistors into a small chip results in circuits that are orders of magnitude smaller, cheaper, and faster than those constructed of discrete electronic components. The IC's mass production capability, reliability and building-block approach to circuit design has ensured the rapid adoption of standardized ICs in place of designs using discrete transistors. ICs are now used in virtually all electronic equipment and have revolutionized the world of electronics
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Paper Data Storage
Paper
Paper
data storage refers to the use of paper as a data storage device. This includes writing, illustrating, and the use of data that can be interpreted by a machine or is the result of the functioning of a machine. A defining feature of paper data storage is the ability of humans to produce it with only simple tools and interpret it visually. Though this is now mostly obsolete, paper was once also an important form of computer data storage.Contents1 History 2 Limits 3 See also 4 References 5 External linksHistory[edit] Before paper was used for storing data, it had been used in several applications for storing instructions to specify a machine's operation. The earliest use of paper to store instructions for a machine was the work of Basile Bouchon
Basile Bouchon
who, in 1725, used punched paper rolls to control textile looms. This technology was later developed into the wildly successful Jacquard loom
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Mellon Optical Memory
Mellon optical memory was an early form of computer memory invented at the Mellon Institute
Mellon Institute
(today part of Carnegie Mellon University) in 1951.[1][2] The device used a combination of photoemissive and phosphorescent materials to produce a "light loop" between two surfaces. The presence or lack of light, detected by a photocell, represented a one or zero. Although promising, the system was rendered obsolete with the introduction of core memory in the early 1950s. It appears that the system was never used in production.Contents1 Description1.1 Writing 1.2 Reading2 ReferencesDescription[edit] The main memory element of the Mellon device consisted of a very large (television sized) square vacuum tube consisting of two slightly separated flat glass plates. The inner side of one of the plates was coated with a photoemissive material that released electrons when struck by light
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Electric Charge
Electric charge
Electric charge
is the physical property of matter that causes it to experience a force when placed in an electromagnetic field. There are two types of electric charges; positive and negative (commonly carried by protons and electrons respectively). Like charges repel and unlike attract. An object with an absence of net charge is referred to as neutral. The SI derived unit of electric charge is the coulomb (C). In electrical engineering, it is also common to use the ampere-hour (Ah), and, in chemistry, it is common to use the elementary charge (e as a unit). The symbol Q often denotes charge
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Bit
The bit (a portmanteau of binary digit)[1] is a basic unit of information used in computing and digital communications. A binary digit can have only one of two values, and may be physically represented with a two-state device. These state values are most commonly represented as either a 0or1. The two values of a binary digit can also be interpreted as logical values (true/false, yes/no), algebraic signs (+/−), activation states (on/off), or any other two-valued attribute. The correspondence between these values and the physical states of the underlying storage or device is a matter of convention, and different assignments may be used even within the same device or program
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EPROM
An EPROM
EPROM
(rarely EROM), or erasable programmable read-only memory, is a type of memory chip that retains its data when its power supply is switched off. Computer memory
Computer memory
that can retrieve stored data after a power supply has been turned off and back on is called non-volatile. It is an array of floating-gate transistors individually programmed by an electronic device that supplies higher voltages than those normally used in digital circuits. Once programmed, an EPROM
EPROM
can be erased by exposing it to strong ultraviolet light source (such as from a mercury-vapor light)
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Twistor Memory
Twistor is a form of computer memory formed by wrapping magnetic tape around a current-carrying wire. Operationally, twistor was very similar to core memory. Twistor could also be used to make ROM memories, including a re-programmable form known as piggyback twistor. Both forms were able to be manufactured using automated processes, which was expected to lead to much lower production costs than core-based systems. Introduced by Bell Labs
Bell Labs
in 1957, the first commercial use was in their 1ESS switch
1ESS switch
which went into operation in 1965. Twistor was used only briefly in the late 1960s and early 1970s, when semiconductor memory devices replaced almost all earlier memory systems
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Plated Wire Memory
Plated wire memory is a variation of core memory developed by Bell Laboratories in 1957. Its primary advantage was that it could be machine-assembled, which potentially led to lower prices than the hand-assembled core. Instead of threading individual ferrite cores on wires, plated wire memory used a grid of wires coated with a thin layer of iron-nickel alloy (called permalloy). The magnetic field normally stored in the ferrite core was instead stored on the wire itself. Operation was generally similar to core, but could also be built with a non-destructive read that did not require refreshing. Plated wire memory has been used in a number of applications, typically in aerospace
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