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Semaphore (lit. ' apparatus for signalling ' ; from Ancient Greek σῆμα ( sêma ) 'mark, sign, token' and Greek -φόρος ( -phóros ) 'bearer, carrier') [ 1 ] is the use of an apparatus to create a visual signal transmitted over distance.
Operation V increments the semaphore S, and operation P decrements it. The value of the semaphore S is the number of units of the resource that are currently available. The P operation wastes time or sleeps until a resource protected by the semaphore becomes available, at which time the resource is immediately claimed. The V operation is the ...
Flag semaphore (from the Ancient Greek σῆμα (sêma) 'sign' and - φέρω (-phero) '-bearer' [1]) is a semaphore system conveying information at a distance by means of visual signals with hand-held flags, rods, disks, paddles, or occasionally bare or gloved hands. Information is encoded by the position of the flags; it is read when the ...
With a sinister hoist, the semaphore flag. P Papa [ˈpa.pə] The Blue Peter. In harbour: All persons should report on board as the vessel is about to proceed to sea. At sea: It may be used by fishing vessels to mean: "My nets have come fast upon an obstruction." Q Quebec [kəˈbɛk] "My vessel is 'healthy' and I request free pratique." R Romeo ...
Semaphores are signalling mechanisms which can allow one or more threads/processors to access a section. A Semaphore has a flag which has a certain fixed value associated with it and each time a thread wishes to access the section, it decrements the flag. Similarly, when the thread leaves the section, the flag is incremented.
Naval flag signalling undoubtedly developed in antiquity in order to coordinate naval action of multiple vessels. In the Peloponnesian War (431 – 401 BCE) squadrons of Athenian galleys were described by Thucydides as engaging in coordinated maneuvers which would have required some kind of communication; [1] there is no record of how such communication was done but flags would have been the ...
President-elect Donald Trump has floated the idea of changing the name of the Gulf of Mexico to the Gulf of America. Here's why that could cause some confusion.
Semaphore is the use of an apparatus with telegraphy to create a visual signal transmitted over long-distances. It may refer more specifically to: Flag semaphore; Semaphore telegraph, a system of long-distance communication based on towers with moving arms; Railway semaphore signal for railway traffic control