CS439: Principles of Computer Systems

Discussion Section 8 Problem Set

Due in Section on Friday, October 31, 2025

The problem set must be completed before section and brought to section. To ensure that your problem set is turned in correctly and that you receive credit for discussion section, you must follow these guidelines exactly.

Include the following header at the top of your file:

Discussion Section Problem Set #:
Student Name:
EID:

You may either type your answers or write them by hand, but you must have a copy with you in discussion section.

In discussion section, your TA will check that you made a good effort on the problem set, you are participating in the discussions in section, and you are ready and able to answer when called upon. If all of those are true, you will receive credit for discussion section that day. Note that a "good effort" on the problem set includes that all answers are in words unique to you and not copied from anywhere else, including the slide deck.

The operating system gives memory to the heap memory manager k page(s) at a time. Why?
Disk requests come into the disk driver for tracks 10, 22, 20, 2, 40, 6, and 38, in that order. A seek takes 6 msec per track moved. How much seek time is needed for the following scheduling algorithms?
a) FIFO
b) SSTF
c) LOOK (SCAN, but doesn't move to the end)
In all cases, the arm is initially at track 20, and you may assume that the head is traveling towards higher numbers.

Adapted from Tannenbaum Chapter 5 Number 24.
Determine the most appropriate form of stable storage for the following scenarios. Explain your reasoning.
1. The University needs to store files for legal purposes. These files are quite large and numerous, but are unlikely to be read.
2. Your parents want to store the data from their security cameras locally.
3. Your friend is building a new computer for general purpose use.
Is it fundamentally necessary to store on disk the information about the unallocated disk sectors? Explain why.
Susan would like to read the file
/usr/susan/cs439/study_guide.txt. Assuming she has the correct permissions and is using FFS, describe the steps the operating system would need to take to read the file.
Some file allocation schemes limit the size of the file whether or not there is enough space for a larger file. Which ones and why?
1. Linked
2. Direct
3. Contiguous
4. Multi-Level index
5. Extents