Semaphore

4 definitions found

From The Collaborative International Dictionary of English v.0.48 [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



From WordNet (r) 2.0 [wn]:

  semaphore
       n : 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

From Moby Thesaurus II by Grady Ward, 1.0 [moby-thes]:

  72 Moby Thesaurus words for "semaphore":
     Roman candle, aid to navigation, alarm, amber light, balefire,
     beacon, beacon fire, bell, bell buoy, blinker, blue peter, buoy,
     caution light, flare, fog bell, fog signal, fog whistle, foghorn,
     glance, go light, gong buoy, green light, heliograph, high sign,
     international alphabet flag, international numeral pennant, kick,
     leer, marker beacon, nod, nudge, parachute flare, pilot flag, poke,
     police whistle, quarantine flag, radio beacon, red flag, red light,
     rocket, sailing aid, semaphore flag, semaphore telegraph, sign,
     signal, signal beacon, signal bell, signal fire, signal flag,
     signal gong, signal gun, signal lamp, signal light, signal mast,
     signal post, signal rocket, signal shot, signal siren,
     signal tower, spar buoy, stop light, the nod, the wink, touch,
     traffic light, traffic signal, watch fire, white flag, wigwag,
     wigwag flag, wink, yellow flag
  
  

From The Free On-line Dictionary of Computing (27 SEP 03) [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-wait}s (or maybe {sleep}s) 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-wait}ing, 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)