resource server
   op Start_Read(i : int), End_Read(i : int)
   op Start_Write(i : int), End_Write(i : int)
body server()
   write("readers and writers server is alive")
   var Readers : int := 0
   var nobody_writing : bool := true

   process serving
      do true ->
         in Start_Read(i) st nobody_writing ->
            Readers++
            write("   age=",age(),"reader",i,"has begun reading, readers=",
               Readers)
         [] End_Read(i) ->
            Readers--
            write("   age=",age(),"reader",i,"finished reading, readers=",
               Readers)
         [] Start_Write(i) st nobody_writing and Readers = 0 ->
            nobody_writing := false
            write("   age=",age(),"WRITER",i,"has begun WRITING")
         [] End_Write(i) ->
            nobody_writing := true
            write("   age=",age(),"WRITER",i,"has finished WRITING")
         ni
      od
   end serving
end server