Security of Computer Systems (CSCT4104)
Computer Science - COS
Semester: Resit
Level: 400
Year: 2016
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SCHOOL: H.T.T.T.C DEPARTEMENT: CS LECTURER(S): Dr. Suh Charles Forbacha
COURSE CODE: CSC316 COURSE TITLE: Security of Computer Systems OPTION: FCS 300
DATE: HALL: …….. TIME: 2 hrs NATURE: EXAM
INSTRUCTION: Please note that the mark that you achieve from this examination will count toward
70% of your final mark for this module.
The following questions are multiple choice. So please select the correct answer from options a-d. NB:
Please note that only one of the answers (a-d) is correct.
RESIT EXAM ; 2014 / 2015 academic year
Duration: 2 hrs
Exercise 1(4 + 8 + 4= 16 marks)
1- Draw the diagram figuring out the place of the operating system within the computer
2- The historical development of operating systems can be subdivided into four generations, each one ultimately tied
to the advances in technology at that moment.
a) Describe, for each generation, from the 2
nd
generation till the 4
th
generation, the main features of operating
systems developed.
b) Provide at least two examples of operating systems developed in each generation.
3- As far as the operating system zoo is concerned, answer the following questions:
a- Differentiate between multiprocessor operating systems and uniprocessor operating systems
b- Differentiate between handheld computer operating systems and embedded operating systems.
Exercise 2: (20 marks)
1. What are the disadvantages of using the following approaches to structure an operating system:
a. Monolithic approach;
b. Layered approach.
2. In the Microkernel approach to system design,
a. Which of the operating system components are susceptible to be put in user space?
b. Why is it preferable to have bugs in user space instead of having it in kernel space?
3. Describe, with the aid of a diagram, the way a client /server model of operating system design can be derived from
the microkernel approach.
4. As far as the virtual machine approach to operating system design is concerned, answer the following questions:
a. What is the difference between Type 1 and Type 2 hypervisors? Name 2 examples of each type.
b. Describe, with the aid of a diagram, how a physical machine is transformed into many virtual machines using
a type 2 hypervisor.
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c. Why is it necessary to have a program handling the sharing of resources among all the virtual machines
created? (Hint: consider a situation where such a program doesn’t exist)
Exercise 3 (18 marks)
1. What is a process?
2. Name the parts of a process’s address space
3. The following are some data structures used by the operating system to handle processes: process control block,
ready queue, waiting queue, processes’ table. What is use of each of these data structures?
4. Draw the diagram representing the process execution states. You should indicate the conditions that make a process
to move from one state to another.
5. What is the difference between a preemptive scheduling algorithm and a non preemptive scheduling algorithm?
Name one example for each type.
6. Considering the following processes found on the ready queue with their execution times given in milliseconds,
draw the diagram representing the order in which they will take turns on the CPU, using the Round Robin
scheduling algorithm with a time quantum of 50 milliseconds (ms).
Exercise 4: ( 2 + 4 + 4 + 6 = 16 marks)
1) What is the importance of a user interface program within a computer system?
2) List some advantages and disadvantages of the following types of user interfaces: Command-line interface, menu
driven interface.
3) Why do some modern operating systems provide a combination of many types of user interface programs at once?
List 2 of those operating systems.
4) Under MS-DOS, what is the use of the following commands: chkdsk, cd, format, help, ren, erase.
Process
P1
P2
P3
P4
P5
Execution time
140 ms
75 ms
320 ms
280 ms
125 ms
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