451:(RAM) is a form of computer data storage. A random-access device allows stored data to be accessed directly in any random order. In contrast, other data storage media such as hard disks, CDs, DVDs and magnetic tape, as well as early primary memory types such as drum memory, read and write data only in a predetermined order, consecutively, because of mechanical design limitations. Therefore, the time to access a given data location varies significantly depending on its physical location. Today, random-access memory takes the form of integrated circuits. Strictly speaking, modern types of DRAM are not random access, as data is read in bursts, although the name DRAM / RAM has stuck. However, many types of SRAM, ROM, OTP, and NOR flash are still random access even in a strict sense. RAM is normally associated with volatile types of memory (such as DRAM memory modules), where its stored information is lost if the power is removed. Many other types of non-volatile memory are RAM as well, including most types of ROM and a type of flash memory called NOR-Flash. The first RAM modules to come into the market were created in 1951 and were sold until the late 1960s and early 1970s.
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flat, circular, usually polycarbonate discs. Data is stored in pits or bumps arranged sequentially on the continuous, spiral track extending from the innermost track to the outermost track, covering the entire disc surface. Data is read by a means of a laser; when the laser enters a pit, the focus of
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uses toroids (rings) of a hard magnetic material (usually a semi-hard ferrite) as transformer cores, where each wire threaded through the core serves as a transformer winding. Two or more wires pass through each core. Magnetic hysteresis allows each of the cores to store a state.
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The mechanical medium utilizes one of the oldest methods of computing and has largely become obsolete. The earliest known method of memory storage and subsequent computerized reading is the
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potential. By asserting or de-asserting the inputs to the CMOS circuit, individual transistors along the pull-up and pull-down networks become
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were a common storage medium for computers from 1900 to 1950. The information was read through a method of identifying the holes in the card.
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placed on it are trapped there and, under normal conditions, will not discharge for many years. When current flow through the MOSFET channel
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layer. The FG is interposed between the CG and the MOSFET channel, and because the FG is electrically isolated by its insulating layer, any
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The magnetic medium is found in magnetic tape, hard disk drives, floppy disks, and so on. This medium uses different patterns of
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to electric current, and results in the desired path connecting from the output node to one of the voltage rails.
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occurs when the physical part of the process fails for some reason, such as dust or dirt entering the drive.
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is an electrical circuit that transforms the physical magnetic flux changes into abstract bits. A
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Performance Silicon Imaging: Fundamentals and Applications of CMOS and CCD Sensors
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circuits. Memory is read through the use of a combination of p-type and n-type
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Flash memory stores information in an array of memory cells made from
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the laser is changed and interpenetrated by the reader's software.
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for erasing. NAND flash memory forms the core of the removable
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is the act of reading one unit of information (e.g. a byte). A
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in a magnetizable material to store data and is a form of
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Complementary metal–oxide–semiconductor (CMOS) is a
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471:Optical storage media writing and reading speed
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65:"Reading" computer
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