Docsity
Docsity
Prepare for your exams
Prepare for your exams

Study with the several resources on Docsity

Earn points to download
Earn points to download

Earn points by helping other students or get them with a premium plan

Guidelines and tips
Guidelines and tips
Sell on Docsity
Sell on Docsity
Docsity AI
Docsity AI
Log inSign up

Prepare for your exams

Study with the several resources on Docsity

Find documents

Prepare for your exams with the study notes shared by other students like you on Docsity

Search for your university

Find the specific documents for your university's exams

Docsity AINEW

Summarize your documents, ask them questions, convert them into quizzes and concept maps

Explore questions

Clear up your doubts by reading the answers to questions asked by your fellow students

Earn points to download

Earn points by helping other students or get them with a premium plan

Share documents
download point icon20 Points

For each uploaded document

Answer questions
download point icon5 Points

For each given answer (max 1 per day)

All the ways to get free points
Get points immediately

Choose a premium plan with all the points you need

Study Opportunities

Choose your next study program

Get in touch with the best universities in the world. Search through thousands of universities and official partners

Community

Ask the community

Ask the community for help and clear up your study doubts

Free resources

Our save-the-student-ebooks!

Download our free guides on studying techniques, anxiety management strategies, and thesis advice from Docsity tutors

Lecture Notes on Operating Systems - Midterm - Fall 2004 | CS 3204, Exams of Operating Systems

Virginia Polytechnic Institute and State University (Virginia Tech)Operating Systems
Prof. William D. Mcquain

Material Type: Exam; Professor: McQuain; Class: Operating Systems; Subject: Computer Science; University: Virginia Polytechnic Institute And State University; Term: Unknown 1989;

Typology: Exams

Pre 2010

Uploaded on 02/13/2009

koofers-user-myc-2
koofers-user-myc-2 🇺🇸

9 documents

1 / 6

Toggle sidebar

This page cannot be seen from the preview

Don't miss anything!

bg1
CS 3204 Operating Systems Midterm Spring 2004
1
V
I
R
G
I
N
I
A
P
O
L
Y
T
E
C
H
N
I
C
I
N
S
T
I
T
U
T
E
A
N
D
S
T
A
T
E
U
N
I
V
E
R
S
I
T
Y
U
T
P
R
O
S
I
M
Instructions:
• Print your name in the space provided below.
• This examination is closed book and closed notes. No calculators or other computing devices may be used.
• Answer each question in the space provided. If you need to continue an answer onto the back of a page, clearly
indicate that and label the continuation with the question number.
• If you want partial credit, justify your answers, even when justification is not explicitly required.
• There are xx questions, priced as marked. The maximum score is 100.
• When you have completed the test, sign the pledge at the bottom of this page and turn in the test.
• Note that either failing to return this test, or discussing its content with a student who has not taken it is a
violation of the Honor Code.
Do not start the test until instructed to do so!
Name
printed
Pledge: On my honor, I have neither given nor received unauthorized aid on this examination.
signed
pf3
pf4
pf5

Partial preview of the text

Download Lecture Notes on Operating Systems - Midterm - Fall 2004 | CS 3204 and more Exams Operating Systems in PDF only on Docsity!

V

IR

G

IN

IA

PO

LYTECHNIC IN ST IT U TE

A N D ST A (^) TE (^) UNIVE

RS

IT

Y U (^) TPROSIM

Instructions:

  • Print your name in the space provided below.
  • This examination is closed book and closed notes. No calculators or other computing devices may be used.
  • Answer each question in the space provided. If you need to continue an answer onto the back of a page, clearly indicate that and label the continuation with the question number.
  • If you want partial credit, justify your answers, even when justification is not explicitly required.
  • There are xx questions, priced as marked. The maximum score is 100.
  • When you have completed the test, sign the pledge at the bottom of this page and turn in the test.
  • Note that either failing to return this test, or discussing its content with a student who has not taken it is a violation of the Honor Code.

Do not start the test until instructed to do so!

Name printed

Pledge: On my honor, I have neither given nor received unauthorized aid on this examination.

signed

  1. [10 points] Consider two processes, P1 and P2, on a multi-tasking operating system with a single CPU. In each of the following situations would it be preferable for the OS to force a context switch and schedule another process? Explain why you reached your conclusion

(a) P1 executes an input operation that requires reading data from a file on disk

(b) P2 executes an arithmetic operation that involves a variable whose value is stored in primary RAM

  1. [10 points] Many modern multi-tasking operating systems use a quantum timer as part of the algorithm for scheduling processes. What is a quantum timer and how is it used?
  2. [10 points] The scheduling algorithm in Windows 3.1 essentially waited for the running process to offer to be moved into the ready state. Describe at least two different (possibly related) problems with this approach?
  1. [10 points] Aside from the technical distinction that fork() spawns a new process and pthread_create() spawns a thread, what is the most significant difference between them from a UNIX programmer's perspective? Assume that the pthread library will, in fact, be available on any UNIX platform.
  2. [10 points] The simple program shown below creates a collection of threads that are intended to cooperate in the initialization of the elements of an array. Will the program always produce correct results, sometimes produce correct results, or never produce correct results? If not, explain how to fix it. If yes, explain why. Assume appropriate includes and declarations necessary for the code to compile and link; that is not the point.

struct Package { int* L; int sIdx; };

... int main() {

pthread_t hThread[MAX_THREADS]; int* List = new int[OFFSET * MAX_THREADS]; Package P[MAX_THREADS];

for (int p = 0; p < MAX_THREADS; p++) { P[p].L = List; P[p].sIdx = p; pthread_create(&hThread[p], NULL, F, (void*) &P[p]); } Print(cout, List); // print contents of array pthread_exit(0); }

void* F(void* D) {

Package* Data = (Package*) D; for (int Idx = Data->sIdx; Idx < OFFSET * MAX_THREADS; Idx += MAX_THREADS) { Data->L[Idx] = Data->sIdx; } pthread_exit(0); }

  1. [10 points] Consider the simple run/ready/block state transition scheme for process scheduling. Draw the state diagram, showing all the possible transitions. Label each transition with a brief, precise description of an event that might cause a process to make that transition.
  2. [10 points] The Linux task state-transition diagram includes a zombie state and a dead state. Evidently, some tasks might be placed in the zombie state before making a final transition to the dead state. Why is this a necessary feature (or at least a useful one)?