Principles of Operating Systems

CMSC 421-01 - Fall 2018

Homework 3

50 points total

Due by 11:59PM EST on Tuesday, December 11th

Please provide written responses to the following question. Be sure to fully answer all questions as they are asked, providing a response of an appropriate length to fully answer the question.

  1. (5 points) Assuming a 1KiB page size, what are the page numbers and offsets for the following address references (all numbers are provided in base-10):
    1. 3040
    2. 4265
    3. 215395
    4. 650341
    5. 2000004
  2. (10 points) Consider the following segment table:
    Segment Base Length
    0 220 650
    1230020
    295105
    31325583
    4195495
    What are the physical addresses for the following logical addresses?
    1. 0, 425
    2. 1, 10
    3. 2, 49
    4. 4, 27
    5. 3, 405
  3. (10 points) On a system with paging, a process cannot access memory that it does not own. Why? How could an operating system allow access to other memory owned by another process? Is this useful? If so, why? If not, why not?
  4. (25 points) Given six partitions of 300KiB, 600KiB, 350KiB, 200KiB, 750KiB, and 125KiB (in that order) with a contiguous memory allocation scheme, how would the first-fit, best-fit, and worst-fit algorithms place processes of size 115KiB, 500KiB, 358KiB, 200KiB, and 375KiB (in that order). Rank the algorithms in terms of how efficiently they use the available memory (how well they resist both internal and external fragmentation) and explain your answer. Assume that the first-fit algorithm begins its search at the beginning of the list of memory holes for each search.

You must submit a PDF file of the answers to these questions on the Homework 3 assignment on Blackboard. You may prepare your responses in any word processing application of your choosing, but you must submit a PDF file. Do not submit Microsoft Word/Apple Pages/LibreOffice documents with your responses. You must convert to a PDF file before submitting or you will lose points.

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