说明：  这是关于操作系统中生产者消费者问题的一段代码，其中生产者和消费者问题是用信号量实现的，临界资源是用数组实现的。
(This is a piece of code about the producer-consumer problem in the operating system, where producer and consumer problems are implemented with semaphores, and the critical resource is implemented as an array.)