Problem 28
What are the various functions of the memory manager in an operating system?
Problem 29
Identify a situation in a multiprogramming system in which a process does not consume the entire time slice allocated to it.
Problem 30
What is meant by an interrupt handler in multiprogramming systems and what is its significance?
Problem 31
Answer each of the following in terms of an operating system that you use: a. How do you ask the operating system to copy a file from one location to another? b. How do you ask the operating system to show you the directory on a disk? c. How do you ask the operating system to execute a program?
Problem 32
Answer each of the following in terms of an operating system that you use: a. How does the operating system restrict access to only those who are approved users? b. How do you ask the operating system to show you what processes are currently in the process table? c. How do you tell the operating system that you do not want other users of the machine to have access to your files?
Problem 33
Explain an important use for the testand-set instruction found in many machine languages. Why is it important for the entire test-and-set process to be implemented as a single instruction?
Problem 35
Students who want to enroll in Model Railroading II at the local university are required to obtain permission from the instructor and pay a laboratory fee. The two requirements are fulfilled independently in either order and at different locations on campus. Enrollment is limited to twenty students; this limit is maintained by both the instructor, who will grant permission to only twenty students, and the financial office, which will allow only twenty students to pay the laboratory fee. Suppose that this registration system has resulted in nineteen students having successfully registered for the course, but with the final space being claimed by two students-one who has only obtained permission from the instructor and another who has only paid the fee. Which requirement for deadlock is removed by each of the following solutions to the problem? a. Both students are allowed in the course. b. The class size is reduced to nineteen, so neither of the two students is allowed to register for the course. c. The competing students are both denied entry to the class and a third student is given the twentieth space. d. It is decided that the only requirement for entry into the course is the payment of the fee. Thus the student who has paid the fee gets into the course, and entry is denied to the other student.
Problem 36
Since each area on a computer's display can be used by only one process at a time (otherwise the image on the screen would be unreadable), these areas are nonshareable resources that are allocated by the window manager. Which of the three conditions necessary for deadlock does the window manager remove in order to avoid deadlock?
Problem 37
Suppose each nonshareable resource in a computer system is classified as a level 1 , level 2 , or level 3 resource. Moreover, suppose each process in the system is required to request the resources it needs according to this classification. That is, it must request all the required level 1 resources at once before requesting any level 2 resources. Once it receives the level 1 resources, it can request all the required level 2 resources, and so on. Can deadlock occur in such a system? Why or why not?
Problem 38
Each of two robot arms is programmed to lift assemblies from a conveyor belt, test them for tolerances, and place them in one of two bins depending on the results of the test. The assemblies arrive one at a time, with a sufficient interval between them. To keep both arms from trying to grab the same assembly, the computers controlling the arms share a common memory cell. If an arm is available as an assembly approaches, its controlling computer reads the value of the common cell. If the value is nonzero, the arm lets the assembly pass. Otherwise, the controlling computer places a nonzero value in the memory cell, directs the arm to pick up the assembly, and places the value 0 back into the memory cell after the action is complete. What sequence of events could lead to a tug-of-war between the two arms?
