操作系统，操作系统课后答案设计现代OS的主要目标是什么? 方便性，有效性，可扩充性和开放性. 2. OS的作用可表现为哪几个方面? a. OS作为用户与计算机硬件系统之间的接口； b. OS作为计算机系统资源的管理者； c. OS实现了对计算机资源的抽象. 7. 实现分时系统的关键问题是什么?应如何解决?-Operating system, after-school answer to the design of modern operating system OS, the main objective? Convenience, efficiency, scalability and openness. 2. OS role in several aspects which can be expressed as? A. OS as a user and computer the interface between the hardware system　b. OS as the computer system resources managers　c. OS implements the abstraction of computer resources. 7. to achieve time-sharing system, the key question is what? should be done?