CS411/511. Operating Systems

Homework 1 - Solutions


1.1. What are the three main purposes of an operating system?

Note that "convenience," "efficiency," etc. are not acceptable answers, since they don't explain "convenient/efficient for whom to do what."

1.4. In a multiprogramming and time-sharing environment, several users share the system simultaneously. This siguation can result in various security problems.
(a) What are two such problems?
(b) Can we ensure the same degree of secutiry in a time-shared machine as we have in a dedicated machine? Explain your answer.

1.6. What are the main differences between operating systems for mainframe computers and personal computers?

1.7. Define the essential properties of the following types of operating systems:
Batch
Interactive
Time-sharing
Real-time
Distributed

1.10. Describe the differences between symmetric and asymmetric multiprocessing. What are three advantages and one disadvantage of multiprocessor systems?


2.3. What are the differences between a trap and an interrupt? What is the use of each function?

2.5. Which of the following instructions should be privileged?

Set value of timer
Read the clock
Clear memory
Turn off interrupts
Switch from user to monitor mode


Answer the following questions about policies and mechanisms:
(a) What is an advantage of separating policy from mechanism in designing any piece of software (including OSs)?

(b) Give three examples of software policies versus mechanisms.