Distributed Processes

type bounded_buffer = process;
  const size = 5;
  var buf: array [1..size] of integer;
      head, tail, count: integer;

  when count > 0:
  procedure get(var x: integer);
  begin
    x := buf[head];
    head := (head mod size) + 1;
    count := count - 1
  end;

  when count < size:
  procedure put(x: integer);
  begin
    buf[tail] := x;
    tail := (tail mod size) + 1;
    count := count + 1
  end;

  begin
    head := 1; tail := 1; count := 0
  end
end;

var b: bounded_buffer;
    v: integer;

begin
  b.put(10);
  b.put(20);
  b.put(30);
  b.get(v);
  writeln(v);  { prints 10 }
  b.get(v);
  writeln(v)   { prints 20 }
end.