Operating System (CS - 308)
Exam I

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Email to : dtnguyen@neiu.edu

    Questions List
 
Question 1
Answer
Question 3
Answer
Question 5
Answer
Question 7
Answer
Question 2
Answer
Question 4
Answer
Question 6
Answer
Question 1

     Give a short definition of an operating system and list a few function that it provides

                Definition:     ____________________________________________________
                                       ____________________________________________________
                                       ____________________________________________________
                                       ____________________________________________________

                Functions:      ____________________________________________________
                                       ____________________________________________________
                                       ____________________________________________________
                                       ____________________________________________________

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Question 2

        List a few criteria that are used in evaluating the performance of the CPU
 

_________
_________
_________
_________

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Question 3

        What is a PCB (Process Control Block)?  Elaborate.

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Question 4

       Given the following processes, use deterministic analysis and Gantt chart to calculate
        which CPU scheduling algorithm will be optimal among
 

Question 5

       What is the completion time of each process for each of the scheduling methods in number
        4 (fill in the table)
 

 
P0
P1
P2
P3
FCFS
       
SRTF
       
PRIORITY
       
RR
       

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Question 6

       What do you know about starvation? How to remedy?

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Question 7

       What do you know about multilevel queue scheduling?

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Answer question 1

        Definition:
 

-*- A program that acts as an intermediary between a user and the computer hardware (and software)

-*- A program that provides an environment in which a user can execute program conveniently and efficiently

-*- A resource allocator and manager

-*- Similar to a government
 

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Answer question 2

        There are three criteria that used in evaluating the performance of the CPU
 

Turn around time
Waiting time
Response time
CPU utilization

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Answer question 3

            It contains many pieces of information associated with a specific process, including;
        process state, program counter, CPU register, CPU scheduling information, memory -
        management information, accounting information, I/O status information

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Answer question 4

            Click on hypertext links in the table below for answers.  For more details in solving
        technique, please see Assignment number one.  In this part, there are only results, not
        explaination.
 

FCFS
SRTF
Priority
RR

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1. FCFS method

FCFS Gantt Chart

 
wt
= 0 + (5 - 1) + (6 - 2) + ( 12 - 3)
= 4 + 4 + 9 = 17
awt
= 17 / 4 = 4.25
==>
 The average waiting time of given jobs is 4.25
   
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2. SRTF algorithm

SRTF Gantt Chart
 
 
wt
= (2 - 1) + 0 + (10 - 2) + (6 - 3)
= 12
awt
= 12 / 4 = 3
==>
The average waiting time of the given jobs is 3
   
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3. Priority method


Priority Gantt Chart

 
wt
= 0 + (5 - 1) + (6 - 3) + (10 - 2)
= 4 + 3 + 8 = 15
awt
= 15 / 4 = 3.75
==>
The average waiting time of the given jobs is 3.75
   
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4. Round robin
     
Process
Arrival time
Burst time
P0
0
5
P1
1
1
P2
2
6
P0
2
Remain 3
P3
3
4
P2
5
Remain 4
P0
7
Remain 1
P3
9
Remain 2
P2
11
Remain 2


Round Robin Gantt Chart

   
 
wt
= (11 - 7) + (5 - 2) + (2 - 1) + (14 - 11) + (9 - 5)  + (3 - 2) + (12 - 9) + ( 7 - 3)
= 4 + 3 + 1 + 3 + 4 + 1 + 3 + 4
= 23
awt
= 23 / 4 = 5.75
==>
The average waiting time of given jobs is 5.75
   
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Answer question 5
 

 
P0
P1
P2
P3
Check results in
FCFS
5
6
12
16
FCFS Gantt Chart
SRTF
6
2
16
10
SRTF Gantt Chart
Priority
5
6
16
10
Priority Gantt Chart
RR
12
3
16
14
RR Gantt Chart

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Answer question 6

            Stavation of low priority process:  Low priority jobs may waits indefinitely the CPU
        if there are always jobs of greater priority.

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Answer question 7

           Multilevel queue scheduling is used to schedule many queue of jobs in defferent levels.
        It helps CPU run faster and finish the jobs in useful ways

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Exam I Page - Copy right Spring 99
Created by Doan nguyen
Last Update March 23, 1999