Page 32 - Electrical Engineering Dictionary

access control a means of allowing ac- time until the desired data rotates under the
cess to an object based on the type of ac- head. (LW)
cess sought, the accessor’s privileges, and the
owner’s policy.
accidental rate the rate of false coinci-
dences in the electronic counter experiment
access control list a list of items associ-
producedbyproductsofthereactionsofmore
ated with a file or other object; the list con-
than one beam particle within the time reso-
tains the identities of users that are permitted
lution of the apparatus.
access to the associated file. There is infor-
mation (usually in the form of a set of bits)
about the types of access (such as read, write, accumulation (1) an increase in the ma-
or delete) permitted to the user. jority carrier concentration of a region of
semiconductor due to an externally applied
access control matrix a tabular repre- electric field.
sentation of the modes of access permitted
from active entities (programs or processes) accumulator (1) a register in the CPU
to passive entities (objects, files, or devices). (processor) that stores one of the operands
A typical format associates a row with an ac- prior to the execution of an operation, and
tive entity or subject and a column with an into which the result of the operation is
object; the modes of access permitted from stored. An accumulator serves as an implicit
that active entity to the associated passive en- source and destination of many of the pro-
tity are listed in the table entry. cessor instructions. For example, register A
of the Intel 8085 is an accumulator. See also
access line a communication line that CPU .
connects a user’s terminal equipment to a
switching node. (2) the storage ring in which successive
pulses of particles are collected to create a
access mechanism a circuit board or an particle beam of reasonable intensity for col-
integrated chip that allows a given part of a liding beams.
computer system to access another part. This
is typically performed by using a specific ac- achievable rate region for a multiple
cess protocol. terminal communications system, a set of
rate-vectors for which there exist codes such
access protocol a set of rules that estab- that the probability of making a decoding er-
lishes communication among different parts. ror can be made arbitrarily small. See also
These can involve both hardware and soft- capacity region, multiple access channel.
ware specifications.

achromatic the quality of a transport line
access right permission to perform an
or optical system where particle momentum
operation on an object, usually specified as
has no effect on its trajectory through the sys-
the type of operation that is permitted, such
tem. In an achromatic device or system, the
as read, write, or delete. Access rights can
output beam displacement or divergence (or
be included in access control lists, capability
both) is independent of the input beam’s mo-
lists, or in an overall access control matrix.
mentum. If a system of lenses is achromatic,
all particles of the same momentum will have
access time the total time needed to re-
equal path lengths through the system.
trieve data from memory. For a disk drive
this is the sum of the time to position the
read/write head over the desired track and the ACI See adjacent channel interference.
c
2000 by CRC Press LLC