说明：  仿真MS_DOS用户访问界面编程 目的：加深对操作系统作为人机接口的认识，初步熟悉编写操作系统接口的步骤和方法
(MS_DOS simulation programming user access interface Objective: To deepen their understanding of the operating system as an awareness of man-machine interface, the initial preparation of the operating system interface familiar with the steps and methods)