.    ,     ,
, , ,   ,   . 
,         ()
.

      ,     -
  ,    .   
 -       
  ,  ,   
 ,      .   -
   (usage count)    (count). 
  ,    ,  -
   ,  ,    -.
          -
  (binary semaphore) (      
     )   
(mutex, ) (      mutual ex-
clusion).  ,       ,
 .        (counting
semaphore, -),     ,  -
  ,      .
-      -
,         -
   .        
 .     .    ,
,  ,     (  -
,  ).

     4 (Edsger Wybe
Dijkstra)  1968     .  
    ()  V (),     
 Proben ()  Verhogen ( ).    -
  down ()  up () .

   Linux     .  down ()
  ,        
.        ,   -
        .  -
   ,        -
    -  .   
       (down)  ,  
.  up ()   ,     -
   .    
(upping) .

  (1930-2002 .)        (,   -
)       .  
          , 
   .     , ,   
     15 .   ,       
  GOTO   Linux.

192                                                                    9