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 Introduction

     A semaphore controls certain states: for example, the states between two
     applications that run on different workstations.  To enable all stations
     to access existing semaphores, each Netware file server has a table
     available to manage these semaphores.

     Semaphores can be interpreted as variables kept on the file server.
     Each semaphore is assigned a name when it is created.  A semaphore name
     can be up to 127 characters long and is not case sensitive.  An
     application can access a semaphore by opening the semaphore with its
     name (NNETSEMOPN()).

     A semaphore can be opened by any number of workstations.  For each
     workstation, the semaphore has the same value.  The semaphore value
     cannot be modified; however, by using specific functions it can be
     incremented (NNETSEMSNG()) or decrements (NNETSEMWAI())
     by 1.

     Each semaphore is assigned information in addition to the semaphore
     value.  For each semaphore, the file server counts the number of
     stations currently accessing the semaphore.  This information can be
     determined with the function NNETSEMOPC().  For example, a semaphore
     named after an application can be used to limit a resource to this
     application.

     Semaphores are often used to implement logical lockings for any kind of
     resource.  A semaphore is assigned to each resource.  Before the
     resource is accessed, the application tries to decrement the semaphore's
     value by one (NNETSEMWAI()).  If the resulting value is negative, the
     resource is locked by another station.  When an application is finished
     using a semaphore's resource, the function NNETSEMSNG() must be called
     to increment the semaphore's value.