-操作系统精髓与设计原理(第五版)+课后题答案1
CHAPTER 2 OPERATING SYSTEM
OVERVIEW
Review Questions
2.1 Convenience: An operating system makes a computer more convenient
to use. Efficiency: An operating system allows the computer system resources to be used in an efficient manner. Ability to evolve: An
operating system should be constructed in such a way as to permit the effective development, testing, and introduction of new system functions without interfering with service.
2.5 The execution context, or process state, is the internal data by which the
operating system is able to supervise and control the process. This
internal information is separated from the process, because the operating system has information not permitted to the process. The context includes all of the information that the operating system needs to manage the
process and that the processor needs to execute the process properly. The context includes the contents of the various processor registers, such as the program counter and data registers. It also includes information of use to the operating system, such as the priority of the process and whether the process is waiting for the completion of a particular I/O event.
Problems
2.1 The answers are the same for (a) and (b). Assume that although processor
operations cannot overlap, I/O operations can. 1 Job: TAT = NT Processor utilization = 50% 2 Jobs: TAT = NT Processor utilization = 100% 4 Jobs: TAT = (2N – 1)NT Processor utilization = 100% 2.4 A system call is used by an application program to invoke a function
provided by the operating system. Typically, the system call results in transfer to a system program that runs in kernel mode.