1.生產者消費者問題
      一個消費者一個生產者時
      semaphore full , empty;
      empty = n , full = 0;
      int in = 0 , out = 0; 
      cobegin 
      process producer () {                       process consumer () { 
               while(true){                                       while(true){
                     produce();                                          P(full);
                     P(empty);                                           out = (out+1)%n;
                     in = (in+1)%n;                                    V(empty);
                     V(full);                                                comsumer();
               }                                                           }
      }                                                       }
      coend      

      而一組消費者，一組生產者時，不僅生產者與消費者之間要同步，而且各個生產者之間、各個消費者之間還必須互斥地訪問緩沖區。
      所以要多一個互斥的信號mutex
      semaphore full , empty , mutex;
      empty = n , full = 0 , mutex = 1;
       int in = 0 , out = 0; 
      cobegin 
      process producer () {                       process consumer () { 
               while(true){                                       while(true){
                     produce();                                          P(full);
                     P(empty);                                           P(mutex) ;  
                     P(mutex) ;                                          out = (out+1)%n;
                     in = (in+1)%n;                                    V(mutex) ; 
                     V(mutex) ;                                          V(empty);
                     V(full);                                                comsumer();
               }                                                           }
      }                                                       }
      coend