CMSC 421 Fall 2015

Midterm Study Guide

General:

Make sure you are able to convert between hexadecimal and decimal values.

Operating System Design:

Name two types of resources that an operating system allocates.
What is the difference between user mode versus kernel mode?
What is the difference between a hardware interrupt and a software trap?
What are the steps involved when making a system call?
Why would a computer ever run a monolithic kernel? Why would it use a microkernel?

Processes:

What are the five different states within the process lifecycle?
Name three different things stored in a process control block.
Name three different situations that can cause a context switch.
What is the difference between an orphan and a zombie?
What do file descriptors do?
Give an example of a Unix signal.
What is the difference between direct and indirect IPC? Give an example of a direct and of an indirect IPC.

Threads:

What is the advantage of a many-to-one threading model versus many-to-many threading?
What is the difference between a race condition versus a deadlock?
For the producer/consumer code on slide 10 of lecture 8, describe the race condition.
For the producer/consumer code on slide 10 of lecture 8, what are some mechanisms that could prevent that race condition?
What can cause a priority inversion?

Scheduling

Be able to differentiate between the different schedulers given a Gantt chart and list of processes.
What is the problem with a purely priority-based scheduler?
For the round-robin scheduler on slide 15 of lecture 11, what is the average waiting time?
Why would a process require hard affinity instead of letting the operating system migrate it to another processor?
Give an example of a system with hard real-time scheduling requirements.

Memory Allocation

How can the operating system provide a contiguous virtual address space to a process, even though physical RAM may be fragmented?
What is the purpose of mmap()?
What does the valid bit do, on a page table entry?
What is the purpose of vfork()?