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Audio Help [sem-uh-fawr, -fohr] Pronunciation Key noun, verb, -phored, -phor·ing. | 1. | an apparatus for conveying information by means of visual signals, as a light whose position may be changed. |
| 2. | any of various devices for signaling by changing the position of a light, flag, etc. |
| 3. | a system of signaling, esp. a system by which a special flag is held in each hand and various positions of the arms indicate specific letters, numbers, etc. |
| 4. | to signal by semaphore or by some system of flags. |
—Related forms
| Dictionary.com Unabridged (v 1.1) Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006. |
semaphore
To learn more about semaphore visit Britannica.com
| © 2008 Encyclopædia Britannica, Inc. |
| sem·a·phore
Audio Help (sěm'ə-fôr', -fōr') Pronunciation Key
n.
tr. & intr.v. sem·a·phored, sem·a·phor·ing, sem·a·phores To send (a message) or to signal by semaphore. [Greek sēma, sign + -phore.] sem'a·phor'ic adj., sem'a·phor'i·cal·ly adv. |
| The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2006 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved. |
semaphore
| Online Etymology Dictionary, © 2001 Douglas Harper |
| semaphore | |
noun | |
| 1. | an apparatus for visual signaling with lights or mechanically moving arms |
verb | |
| 1. | send signals by or as if by semaphore |
| 2. | convey by semaphore, of information |
| WordNet® 3.0, © 2006 by Princeton University. |
semaphore [ˈseməfoː] noun
Example: He signalled the message to them in semaphore.
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| Kernerman English Multilingual Dictionary, © 2000-2006 K Dictionaries Ltd. |
semaphore programming, operating system
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)
| The Free On-line Dictionary of Computing, © 1993-2007 Denis Howe |
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.| Webster's Revised Unabridged Dictionary, © 1996, 1998 MICRA, Inc. |
semaphore
semaphore: in CancerWEB's On-line Medical Dictionary
| On-line Medical Dictionary, © 1997-98 Academic Medical Publishing & CancerWEB |
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