| slovo | definícia |
semaphore
(encz) | semaphore,semafor n: Zdeněk Brož |
semaphore
(encz) | semaphore,signalizace n: Zdeněk Brož |
Semaphore
(gcide) | Semaphore \Sem"a*phore\, n. [Gr. sh^ma a sign + fe`rein to bear:
cf. F. s['e]maphore.]
A signal telegraph; an apparatus for giving signals by the
disposition of lanterns, flags, oscillating arms, etc.
[1913 Webster] Semaphoric |
semaphore
(wn) | semaphore
n 1: an apparatus for visual signaling with lights or
mechanically moving arms
v 1: send signals by or as if by semaphore
2: convey by semaphore, of information |
semaphore
(foldoc) | semaphore
The classic method for
restricting access to shared resources (e.g. storage) in a
multi-processing environment. They were invented by
Dijkstra and first used in T.H.E operating system.
A semaphore is a protected variable (or {abstract data
type}) which can only be accessed using the following
operations:
P(s)
Semaphore s;
{
while (s == 0) ; /* wait until s>0 */
s = s-1;
}
V(s)
Semaphore s;
{
s = s+1;
}
Init(s, v)
Semaphore s;
Int v;
{
s = v;
}
P and V stand for Dutch "Proberen", to test, and "Verhogen",
to increment. The value of a semaphore is the number of units
of the resource which are free (if there is only one resource
a "binary semaphore" with values 0 or 1 is used). The P
operation busy-waits (or maybe sleeps) until a resource is
available whereupon it immediately claims one. V is the
inverse, it simply makes a resource available again after the
process has finished using it. Init is only used to
initialise the semaphore before any requests are made. The P
and V operations must be indivisible, i.e. no other process
can access the semaphore during the their execution.
To avoid busy-waiting, a semaphore may have an associated
queue of processes (usually a FIFO). If a process does a
P on a semaphore which is zero the process is added to the
semaphore's queue. When another process increments the
semaphore by doing a V and there are tasks on the queue, one
is taken off and resumed.
(1995-02-01)
|
| | podobné slovo | definícia |
semaphore
(encz) | semaphore,semafor n: Zdeněk Brožsemaphore,signalizace n: Zdeněk Brož |
semaphore plant
(encz) | semaphore plant, n: |
semaphore
(wn) | semaphore
n 1: an apparatus for visual signaling with lights or
mechanically moving arms
v 1: send signals by or as if by semaphore
2: convey by semaphore, of information |
semaphore plant
(wn) | semaphore plant
n 1: erect tropical Asian shrub whose small lateral leaflets
rotate on their axes and jerk up and down under the
influence of sunshine [syn: telegraph plant, {semaphore
plant}, Codariocalyx motorius, Desmodium motorium,
Desmodium gyrans] |
semaphore
(foldoc) | semaphore
The classic method for
restricting access to shared resources (e.g. storage) in a
multi-processing environment. They were invented by
Dijkstra and first used in T.H.E operating system.
A semaphore is a protected variable (or {abstract data
type}) which can only be accessed using the following
operations:
P(s)
Semaphore s;
{
while (s == 0) ; /* wait until s>0 */
s = s-1;
}
V(s)
Semaphore s;
{
s = s+1;
}
Init(s, v)
Semaphore s;
Int v;
{
s = v;
}
P and V stand for Dutch "Proberen", to test, and "Verhogen",
to increment. The value of a semaphore is the number of units
of the resource which are free (if there is only one resource
a "binary semaphore" with values 0 or 1 is used). The P
operation busy-waits (or maybe sleeps) until a resource is
available whereupon it immediately claims one. V is the
inverse, it simply makes a resource available again after the
process has finished using it. Init is only used to
initialise the semaphore before any requests are made. The P
and V operations must be indivisible, i.e. no other process
can access the semaphore during the their execution.
To avoid busy-waiting, a semaphore may have an associated
queue of processes (usually a FIFO). If a process does a
P on a semaphore which is zero the process is added to the
semaphore's queue. When another process increments the
semaphore by doing a V and there are tasks on the queue, one
is taken off and resumed.
(1995-02-01)
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