本次实验的目的在于掌握使用nachos中的线程序解决较为复杂的并发问题。实验内容分三部分：实现事件栅栏原语并进行正确性测试；实现闹钟原语并进行正确性测试；利用事件栅栏和闹钟原语来解决电梯问题（详细内容请看nachos-labs.pdf）。-this experiment designed to use the line of nachos procedures to address more complex issues of concurrency. Experimental content is divided into three parts : to achieve the original language fence incident and accuracy testing; Achieve clock original language and accuracy testing; Using Event fence and alarm clock to solve the original language Elevator (See details nachos - labs.pdf ).