Exam Study Guide

Chapter 5: Input/Output Must have a familiarity with the issues associated with I/O. –For example, why is so much attention paid to the I/O sub- system by system designers? –What are the two basic categories of I/O devices? –How does the OS interface with the I/O devices? –And so forth. Make sure you understand Memory-Mapped I/O very well. Make sure you understand DMA very well.

Make sure you understand the more precise discussion on interrupts. You need to understand very well Section 5.5 that discusses hardware and software related to clocks. Make sure you understand the basics of the device drivers.

Sections From Chapter 5 for Which You are Responsible All pages up to (but not including) Section 5.2. Section 5.3 up to (but not including) Section All of Section 5.5.

File Systems This is considered a very important issue and you need to understand it very well. The only part of this chapter that will not be covered on the exam is the Section on Backups. You need to be familiar with the discussion on file systems from a user perspective. This includes: –File naming –File Structure –File types –File Access –File Operations –How to use I/O calls in a program.

You need to have a firm grasp on: –Memory-Mapped Files –Directory structure –Path Names

File System Implementation You must be very knowledgeable with the implementation issues. This includes (but is not limited to): –File system layout. –The three methods of keeping track of which blocks belong to which files. You should understand clearly the advantages and disadvantages of each approach (if such disadvantages exists). If a File Allocation Table or set of i-nodes are given, you need to be able to find all of the blocks belonging to that file. You must know how directories are implemented and any issues associated with such an implementation.

You need to understand links: –What are the two methods of creating a link? –What are the issues associated with each method? –Why are links useful? You need to understand the trade-offs in the various approaches to disk space management. This includes: –Block size –Keeping track of free disk blocks –Disk quotas.

Skip the section on backups and resume at File System Consistency. You need to understand the checks for consistency provided in the text. You need to know the techniques for increasing file system importance. Skip the section on Log-Structured files.

You must! Understand the example file systems discussed at the end of the chapter and how each approaches the various implementation issues. You MUST be able to work through problems such as Figure You might want to look at and work through problems 11,12,17,22, 27,28, and inclusive. The exam will also re-visit virtual memory (in light of all you have learned doing part 3 of the B-project.