| 释义 |
memory
Physics
(in computing) The part of a computer in which data is stored while it is being worked on. A typical microcomputer, for example, has a comparatively small amount of read-only memory and a large amount of random-access memory. Only data in ROM is preserved when the machine is switched off; any data in RAM must be saved to disk if it is wanted again.
Computer
A device or medium that can retain information for subsequent retrieval. The term is synonymous with storage and store, although it is most frequently used for referring to the internal storage of a computer that can be directly addressed by operating instructions. See also cache, main memory, memory hierarchy, memory management, semiconductor memory.
Electronics and Electrical Engineering
Any device or physical medium associated with a computer and used to store information for subsequent retrieval. The information may, for example, be computer programs or the data on which programs operate. The information is stored in digital form as sequences of bits. The location of each item of information (usually in the form of a word or byte) can be identified by a unique address, which allows a particular item to be stored (or written) and retrieved (or read). The time taken to retrieve an item of information from memory is known as the access time. The memory capacity is the total amount of information, usually in terms of the number of bits or bytes, that can be stored in any given memory, or in a computer system as a whole. A computer system contains several types of memory that differ markedly in access time and capacity, and also in the amount of information that can be read or written on a given occasion and the cost of storing a given amount of information. For efficient and economical use of computer memory, the various types are organized into a hierarchy according to performance and cost. The highest performance and in general most expensive type is at the top level of the hierarchy, and is the internal register storage under the direct control of the central processing unit (CPU) used to assist in the execution of machine instructions. The main working data and code of a running program, and intermediate or partial results too large to fit into registers are stored in RAM (random-access memory), composed of solid-state electronic circuitry with access times of tens of nanoseconds; the stored information can be readily altered. To speed up program execution, relatively small-capacity solid-state cache memory with extremely short access time is often inserted between the CPU and the main memory. In modern multicore processors there are routinely three levels of cache between the processor registers and RAM. Backing store is below solid-state memory in the hierarchy. It is nonvolatile memory on which information is held for reference but not for direct execution. Permanently connected (online) backing store is usually in the form of magnetic disk memory, and the information is transferred to and from the main memory by means of a disk drive. The capacity of disk memory is very much larger than solid-state memory and it is much less expensive, but the access time is reckoned in milliseconds. Information is also held offline on, for example, floppy disks, CD-ROM, or magnetic tape, and these storage devices are at the lowest levels of the hierarchy. More recent developments have backing store implemented using solid-state flash memory configured to mimic the behaviour of magnetic disk drives. http://computer.howstuffworks.com/computer-memory1.htm Computer memory basics, on the howstuffworks website
Biology
The means by which information is stored in the brain. The exact mechanism of processing and storing information is not known but is thought to involve the construction of circuits of neurons in the cerebral cortex, which are strengthened by repeated use (see synaptic plasticity). Various models of memory have been proposed, with different types of information and levels of processing. One model proposes three principal forms of memory based on duration. Sensory memory is the fleeting retention of stimuli perceived by the senses. These memories are almost immediately lost unless attention is paid to them, when they enter short-term memory (or ‘working memory’). This lasts for up to a minute or so. With effort, for example repetition of a phone number, the information may then enter long-term memory, where it can remain for hours, days, or even years. The subsequent conscious recollection of things or facts involves explicit (declarative) memory, whereas implicit memory concerns motor skills, such as the ability to ride a bike, and conditioned reflexes. The transfer of short-term memory to long-term memory involves the limbic system, in particular the hippocampus. It is thought that connections in the hippocampus are necessary for consolidating and accessing short-term memory but not for recalling long-term memories. The amygdala is instrumental in producing fear and fear memories. Memory is essential to the processes of learning and recognition of individuals and objects. https://plato.stanford.edu/entries/memory/ Comprehensive account of concepts and models of memory, from the Stanford Encyclopedia of Philosophy
Geography
The recollection of the past. We construct meaning about our lives and worlds through the places we create, inhabit, or visit. Till (1999, Ecumene 6) describes places as ‘fluid mosaics of memory, metaphor, matter and experience, [which] create and mediate social spaces and temporalities’. Hoelscher and Alderman (2004, Soc. & Cult. Geog. 5, 3, special issue), observe that ‘memory and place conjoin to produce much of the context for modern identities’. Look for O. Jones and J. Garde-Hansen (2012). Tolia-Kelly (2004, TIBG 29, 3) writes on re-memory: ‘a conceptualization of encounters with memories, stimulated through scents, sounds and textures in the everyday…souvenirs…[and] signifiers of “other” narrations of the past, not directly experienced’.
Philosophy
The power of the mind to think of a past that no longer exists poses both empirical, psychological problems, and more abstract philosophical ones. The scientist wants to know how the brain stores its memories, and whether the mechanism is similar for different types of memory, such as short-term and long-term memories. The philosopher is particularly puzzled by the representative power of memory. That is, if I summon up a memory of some event, how do I know to interpret it as representing the past, rather than being a pure exercise of imagination? Is there a specific ‘feeling of pastness’? But if so, might I not then have the feeling, but not know to interpret that as a feeling of pastness? Indeed, is there always a present representation, or might memory be a form of direct acquaintance with the past? This might at least give us a justification of the confidence we place in memory. But is not the sceptical hypothesis proposed by Russell, that the earth might have sprung into existence five minutes ago, with a population that ‘remembers’ a wholly unreal past, at least logically possible? But if it is logically possible, the question of how we know that this is not what has happened is set to look intractable.
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