<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.
The most common form of RAM in use today is built from
semiconductor integrated circuits, which can be either
static (SRAM) or dynamic (DRAM). In the 1970s magnetic
core memory was used. RAM is still referred to as core by
some old-timers.
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.
(1995-12-05)
Nearby terms:
RAMIS II « RAMTRON « random « random-access memory » Random Access Memory Digital-to-Analog Converter » randomness » random numbers
