Random-access memory

random-access memory
    n 1: the most common computer memory which can be used by
         programs to perform necessary tasks while the computer is
         on; an integrated circuit memory chip allows information to
         be stored or accessed in any order and all storage
         locations are equally accessible [syn: {random-access
         memory}, {random access memory}, {random memory}, {RAM},
         {read/write memory}]
    

random-access memory

   <storage> (RAM) (Previously "direct-access memory").  A data
   storage device for which the order of access to different
   locations does not affect the speed of access.  This is in
   contrast to, say, a {magnetic disk}, {magnetic tape} or a
   {mercury delay line} where it is very much quicker to access
   data sequentially because accessing a non-sequential location
   requires physical movement of the storage medium rather than
   just electronic switching.

   In the 1970s {magnetic core} memory was used and some
   old-timers still call RAM "core".  The most common form of RAM
   in use today is {semiconductor} {integrated circuits}, which
   can be either {static random-access memory} (SRAM) or {dynamic
   random-access memory} (DRAM).

   The term "RAM" has gained the additional meaning of
   read-write.  Most kinds of semiconductor {read-only memory}
   (ROM) are actually "random access" in the above sense but are
   never referred to as RAM.  Furthermore, memory referred to as
   RAM can usually be read and written equally quickly
   (approximately), in contrast to the various kinds of
   {programmable read-only memory}.  Finally, RAM is usually
   volatile though {non-volatile random-access memory} is also
   used.

   Interestingly, some {DRAM} devices are not truly random access
   because various kinds of "{page mode}" or "column mode" mean
   that sequential access is faster than random access.

   The humorous expansion "Rarely Adequate Memory" refers to the
   fact that programs and data always seem to expand to fill the
   memory available.

   (2007-10-12)