Memory

memory, in computing

memory, in computing: see computer.

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memory, in psychology

memory, in psychology, the storing of learned information, and the ability to recall that which has been stored. It has been hypothesized that three processes occur in remembering: perception and registering of a stimulus; temporary maintenance of the perception, or short-term memory; and lasting storage of the perception, or long-term memory. Two major recognized types of long-term memory are procedural memory, involving the recall of learned skills, and declarative memory, the remembrance of specific stimuli. For long-term memory to occur, there must be a period of information consolidation.

The process of forgetting was first studied scientifically by Hermann Ebbinghaus, a German experimental psychologist, who performed memory tests with groups of nonsense syllables (disconnected syllables without associative connection). Ebbinghaus showed that the rate of forgetting is greatest at first, gradually diminishing until a relatively constant level of retained information is reached. Theories to explain forgetting include the concept of disuse, which proposes that forgetting occurs because stored information is not used, and that of interference, which suggests that old information interferes with information learned later and new information interferes with previously learned information.

In some instances, memory loss is an organic, physiological process. Retrograde amnesia, i.e., the failure to remember events preceding a head injury, is evidence of interrupted consolidation of memory. In anterograde amnesia, events occurring after brain damage—e.g., in head injury or alcoholism—may be forgotten. Memory loss may also result from brain cell deterioration following a series of strokes, cardiovascular disease, or Alzheimer's disease (see dementia).

Physiologically, learning involves modification of neural pathways. PET scans and related studies have shown certain parts of the brain, such as the frontal lobe of the cerebral cortex and a structure called the hippocampus, to be particularly active in recall. Computer models of brain memory are called neural networks. In a study using genetic manipulation, a mouse with enhanced memory capabilities has been produced.

Bibliography

See M. H. Ashcroft, Human Memory and Cognition (1989, repr. 1994); N. Cowan, Attention and Memory (1995, repr. 1998); J. McConkey, ed. The Anatomy of Memory (1996); D. L. Schacter, Searching for Memory (1996) and The Seven Sins of Memory (2001); J. A. Groegerd, Memory and Remembering (1997); A. Baddeley, Human Memory (rev. ed. 1998); R. Rupp, Committed to Memory (1998).

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memory

In digital computers, a physical device used to store such information as data or programs on a temporary or permanent basis. Most digital computer systems have two types of memory, the main memory and one or more auxiliary storage units. In most cases, the main memory is a high-speed RAM. Auxiliary storage units include hard disks, floppy disks, and magnetic tape drives. Besides main and auxiliary memories, other forms of memory include ROM and optical storage media such as videodiscs and compact discs (see CD-ROM).

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memory

Power or process of recalling or reproducing what has been learned or experienced. Research indicates that the ability to retain information is fairly uniform among normal individuals; what differs is the degree to which persons learn or take account of something to begin with and the kind and amount of detail that is retained. Attention, motivation, and especially association facilitate this process. Visual images are generally better remembered than are other forms of sense-data. Memory prodigies, or people with “photographic” or “eidetic” memories, often draw heavily on visual associations, including mnemonics. Many psychologists distinguish between short- and long-term memory. The former (variously said to last 10 seconds to 3 minutes) is less subject to interference and distortion than the latter. Long-term memory is sometimes divided into episodic (i.e., event-centred) and semantic (i.e., knowledge-centred) memory. Various models of memory have been proposed, from the Enlightenment notion of impressions made on brain tissues (restyled as “memory molecules” or coded “engrams” in the 20th century) to B.F. Skinner's “black box” to more recent ideas concerning information processing or the formation of neuronal groups. Disorders of or involving memory include Alzheimer disease, amnesia, Korsakoff syndrome, post-traumatic stress disorder, and senile dementia. See also hypnosis.

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The computer's workspace, which is physically a collection of dynamic RAM (DRAM) chips. It is a major resource in the computer because it determines the size and number of programs that can be run at the same time, as well as the amount of data that can be processed instantly.

It All Takes Place in Memory
All program execution and data processing takes place in memory, often called "main memory" to differentiate it from memory chips on other circuit boards in the machine. The program's instructions are copied into memory from disk, tape or from the network and then extracted from memory into the control unit circuit for analysis and execution. The instructions direct the computer to input data into memory from a keyboard, disk, tape, modem or network.

Calculate, Compare and Copy
As data are entered into memory, the previous contents of that space are lost. Once the data are in memory, they can be processed (calculated, compared and copied). The results are sent to a screen, printer, disk, tape, modem or network.

An Electronic Checkerboard
Memory is like an electronic checkerboard, with each square holding one byte of data or instruction. Each square has a separate address like a post office box and can be manipulated independently. As a result, the computer can break apart programs into instructions for execution and data records into fields for processing. See early memories and RAM.

A Checkerboard of Bytes

Each checkerboard square of memory holds one byte. The contents of any single byte or group of bytes can be calculated, compared and copied independently. That is how fields are put together to form records and broken apart when read back in. On a disk, data are stored in sectors, typically 512 bytes long, that are the smallest unit that can be read or written by the drive.

Memory Does Not Remember
Oddly enough, the computer's memory does not "remember" anything when the power is turned off. So why do they call it memory? Because the first memory did "remember," but today's RAM chips do not, which is why files have to be saved before the application is ended. Although there are memory chips that do hold their content permanently (ROMs, PROMs, EPROMs, Flash, etc.), they are used for internal control purposes and not for the user's data. Just to bewilder you more, it is quite possible that in the future, memory will again "remember" (see future RAM chips).

"Remembering" memory in a computer system is its disks and tapes, and although they are sometimes called "memory devices," many prefer to call them "storage devices" (as we do) in order to differentiate them from internal memory.

Memory Can Get Clobbered!
Memory is an important resource that cannot be wasted. It must be allocated by the operating system as well as by applications and then released when not needed. Errant programs can grab memory and not let go of it, which results in less and less memory available as you load and use more programs. Restarting the computer gives memory a clean slate, which is why rebooting the computer clears up so many problems with applications.

In addition, if the operating system has bugs, a malfunctioning application can write into the same memory used by another program, causing all kinds of unspecified behavior. You discover it when the system freezes or something weird happens all of a sudden. If you were to be able to look into memory and watch how fast data and instructions are written into and out of it in the course of even 10 minutes, you would know it is truly a miracle that it works at all.

Other terms for the computer's main memory are RAM, primary storage and read/write memory. Earlier terms were core and core storage. See dynamic RAM, static RAM and memory module.

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Memory

Mercy (See FORGIVENESS.)

Aethalides

herald of the Argonauts; had perfect memory. [Gk. Myth.: Kravitz, 11]

Balderstone, Thomas

knew all of Shakespeare by heart. [Br. Lit.: Sketches by Boz]

Eunoe

river whose water sparks remembrance of kindnesses. [Ital. Lit.: Purgatory, 33]

Fahrenheit 451

in a future America where books are prohibited, a group of people memorize texts in order to preserve their content. [Am. Lit.: Bradbury Fahrenheit 451 in Weiss, 289]

madeleine

cookie that awakened the stream of Marcel’s recollections. [Fr. Lit.: Proust Remembrance of Things Past]

Memory, Mr.

during his stage performance his feats of memory enable him to signal clues to a man trying to thwart England’s enemies. [Eng. Cinema: The 39 Steps]

Mneme

Boeotian wellspring which whetted the memory. [Gk. Myth.; Wheeler, 713]

Mnemosyne

goddess of memory; mother of Muses. [Gk. Myth.: Espy, 20]

Munin

one of Odin’s ravens; regarded as embodying memory. [Norse Myth.: Leach, 761]

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(storage)

memory - These days, usually used synonymously with Random Access Memory or Read-Only Memory, but in the general sense it can be any device that can hold data in machine-readable format.