操作系统精髓与设计原理第五版 课后题答案
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.
CHAPTER 3
PROCESS DESCRIPTION AND
CONTROL
Review Questions
3.5 Swapping involves moving part or all of a process from main memory
to disk. When none of the processes in main memory is in the Ready state, the operating system swaps one of the blocked processes out onto disk into a suspend queue, so that another process may be brought into main memory to execute.
3.10 The user mode has restrictions on the instructions that can be executed
and the memory areas that can be accessed. This is to protect the operating system from damage or alteration. In kernel mode, the operating system does not have these restrictions, so that it can perform its tasks. Problems
3.1 ?Creation and deletion of both user and system processes. The
processes in the system can execute concurrently for information sharing, computation speedup, modularity, and convenience.
Concurrent execution requires a mechanism for process creation and deletion. The required resources are given to the process when it is created, or allocated to it while it is running. When the process terminates, the OS needs to reclaim any reusable resources. ?Suspension and resumption of processes. In process scheduling, the
OS needs to change the process's state to waiting or ready state when it is waiting for some resources. When the required resources are available, OS needs to change its state to running state to resume its execution. ?Provision of mechanism for process synchronization. Cooperating
processes may share data. Concurrent access to shared data may result in data inconsistency. OS has to provide mechanisms for processes synchronization to ensure the orderly execution of cooperating processes, so that data consistency is maintained. ?Provision of mechanism for process communication. The processes
executing under the OS may be either independent processes or cooperating processes. Cooperating processes must have the means to communicate with each other. ?Provision of mechanisms for deadlock handling. In a
multiprogramming environment, several processes may compete for a finite number of resources. If a deadlock occurs, all waiting
操作系统精髓与设计原理第五版 课后题答案
