random access memory (RAM)
direct-
access read/write storage in which each ad-
dressable unit has a unique hardwired ad-
dressing mechanism. The time to access a
randomly selected location is constant and
not dependent on its position or on any previ-
ous accesses. The RAM has a set of k address
lines (
m = 2
k
), n bidirectional data lines, and
a set of additional lines to control the direc-
tion of the access (read or write), operation
and timing of the device.
RAM is commonly used for the main
memory of a computer and is said to be static
if power has to be constantly maintained in
order to store data and dynamic if periodic
absences of power do not cause a loss of
data. RAM is usually volatile. See also
static
random access memory
,
dynamic random
access memory
,
nonvolatile random-access
memory
.
random behavior
response without a
spectral or amplitude pattern or relationship
to the excitation. The excitation may be in-
ternal, and may be thermal in nature.
random coding
coding technique in
which codewords are chosen at random ac-
cording to some distribution on the codeword
symbols. Commonly a tool used in the devel-
opment of information theoretic expressions.
random logic
a digital system con-
structed with logic gates and flip-flops
and other basic logic components intercon-
nected in an non-specific manner. See also
microprogramming
.
random process
a mathematical pro-
cedure for generating random numbers to
a specific rule called a process,
x which
is defined on continuous
x(t), t ∈ R
n
,
or discrete
x(k), k ∈ Z
n
space / time.
The value of the process at each point in
space or time is a random vector. See also
random variable
,
random vector
.
See
also
correlation
,
covariance
,
autocorrelation
,
autocovariance
.
random replacement algorithm
in a
cache or a paging system, an algorithm that
chooses the line or page in a random man-
ner. A pseudo-random number generators
may be used to make the selection, or other
approximate method. The algorithm is not
very commonly used, though it was used in
the translation buffers of the VAX11/780 and
the Intel i860 RISC processor.
random signal
a signal
X(t) that is either
noise
N(t), an interfering signal s(t), or a
sum of these:
X(t) = s
1
(t)+· · ·+s
m
(t)+N
1
(t)+· · ·+N
n
(t)
random testing
the process of testing us-
ing a set of pseudo-randomly generated pat-
terns.
random variable
a continuous or discrete
valued variable that maps the set of all out-
comes of an experiment into the real line (or
complex plane). Because the outcomes of
an experiment are inherently random, the fi-
nal value of the variable cannot be predeter-
mined.
random vector
a vector (typically a col-
umn vector) of random variables. See also
random variable
,
random process
.
randomized decision rule
a hypothesis
decision/classification rule that is not deter-
ministic (that is, the measurement or obser-
vation does not uniquely determine the de-
cision). Although typically not useful given
continuous observations, a randomized rule
can be necessary given discrete observations.
See also
receiver
operating characteristics
curve
.
range filter
an edge detection filter that
finds edges by taking the difference between
the maximum and minimum values in a lo-
cal region of the image. The range filter also
accepts a weight mask the size of the local
image region that controls pixel values be-
fore they enter the minimum and maximum
c
2000 by CRC Press LLC