Page 40 - Electrical Engineering Dictionary

length or size of the address fields in the in- addressing range numbers that define
struction. the number of memory locations addressable
by the CPU. For a processor with one address
address space an area of memory seen or space, the range is determined by the number
used by a program and generally managed as of signal lines on the address bus of the CPU.
a continuous range of addresses. Many com-
puters use separate address spaces for code adequate service in terms of the block-
and data; some have other address spaces ing probability, term associated with a fixed
for system. An address space is usually sub- blocking. A typically quoted value may be
ject to protection, with references to a space 2. See also blocking.
checked for valid addresses and access (such
as read only). adiabatic a system that has no heat trans-
fer with the environment.
The physical address space of a computer
(2 32 bytes, and up to 2 64 bytes) is often larger
adiabatic cooling a process where the
than the installed memory. Some parts of the
temperature of a system is reduced without
address range (often at extreme addresses)
any heat being exchanged between the sys-
may be reserved for input–output device ad-
tem and its surroundings. In particle beam
dresses. See also byte, memory, memory acceleration this term is used to describe the
mapped I/O.
process in the particle source storage ring
where beam emittances are reduced without
addresstranslation Seeaddressmapping. affecting beam energy.
adiabatic following an approximation
addressing (1) in processors: a mecha- made when some states in a quantum me-
nismtorefertoadeviceorstoragelocationby chanical system respond to perturbations
an identifying number, character, or group of more quickly than the other states. In this
characters. That may contain a piece of data approximation the rapidly responding states
or a program step. are assumed to depend only on the instanta-
neous values of the other states and are said
(2) in networks, the process of identify-
to “follow” those states.
ing a network component, for instance, the
unique address of a node on a local area net-
adiabaticpassage a technique for the cre-
work.
ation of a long-lived coherence in a quantum
mechanical system by manipulating electro-
addressing fault an error that halts the magnetic field intensities so that the system
mapper when it cannot locate a referenced always remains in an eigenstate. In practice,
object in main memory. this involves changing field strengths on a
time scale slower than the inverse of the en-
addressing mode a form of specifying ergy spacing between relevant eigenstates of
the address (location) of an operand in an the system. For example, consider a lambda
instruction. Some of the addressing modes system in which only one field is present ini-
found in most processors are direct or register tially and all population starts out in the un-
direct, wheretheoperandisinaCPUregister; coupled ground state. If a field is gradually
register indirect (or simply indirect), where turned on to couple this initial state to the ex-
a CPU register contains the address of the cited state, the system can remain transparent
operand in memory; immediate, where the by evolving in such a way that it is always
operand is a part of the instruction. See also mathematically equivalent to the dark state
central processing unit. that would be produced by coherent popu-

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2000 by CRC Press LLC