Test Prep CS 490 Test 1

Semaphore Primitives

Figure 5.10 A Correct Solution to the Infinite-Buffer Producer/Consumer Problem Using Binary Semaphores

How to Prepare – all topics  Make an outline for each subject/topic  For each major idea, write a short paragraph summarizing the main points  Be sure to know definitions of terms, so you can understand the questions.

Other Tips  Review your homework and read my comments. If I said your answers were vague, focus on being more specific. If I said your answers were vague, focus on being more specific. If I said “correct, but not necessary”, focus on answering the question that was asked, do not feel like you must give lots of background. If I said “correct, but not necessary”, focus on answering the question that was asked, do not feel like you must give lots of background.  Read the question carefully and do what it says!!

Exam Format  Multiple choice, matching or other objective question  Short answer Comparisons Comparisons “What’s the significance of this concept” “What’s the significance of this concept” State the main concept/purpose/reason State the main concept/purpose/reason  Problems, similar to those on homework  Program 1

What Is a Good Answer?  The facts are right.  It is not just something you have memorized and regurgitated  It answers the question I asked, not the question you thought I would ask.  It addresses the main points and does not focus on side issues.  It is not vacuous  It is organized and coherent: not just a collection of key words strung together

For Example  Question: “Compare an apple and an orange.”  Bad Answer: “An apple is red and crunchy ; an orange is juicy, and a member of the citrus genus.”  Better: “Apples and oranges are both fruits and have a round shape. Apples are from the genus malus and oranges from the citrus genus. Apples are usually red, oranges are orange.”  In other words, compare by looking at the same attributes in both and deciding how they are the same or different.

Compare Example  If you just describe and evaluate each separately, you will not get full credit.  Use phrases like “A does it this way; on the other hand, B does it that way”, or “A and B both do this”.

For Example  Question: Give a significant difference betw. the FCFS scheduling algorithm and RR scheduling.  Good Answer: “FCFS allows processes to run until they block or terminate. RR allows processes to run until they exceed a pre- determined time-slice.” or “FCFS allows the process to decide how long it runs but RR has an upper limit to how long a process can run before another process is allowed to execute.”  Bad : “RR uses time-slices, FCFS doesn’t”  Notice: none of them define RR or FCFS

Significant Difference Example  Significant differences usually should be a difference in method or approach, not an effect of that method. So rather than say “A is more efficient than B” give the difference in method or structure that causes A to be more efficient.

Vacuous answers - for example  Question: “What is virtual memory?”  Vacuous Answer: “Virtual memory is a very important memory management technique. Today, almost all computers employ some form of virtual memory. Virtual memory is implemented by the memory management portion of the operating system. It requires special computer hardware and software. Computers without virtual memory are not as efficient or user-friendly as computers with virtual memory…blah, blah, blah.”