Cisy 300:Computer Operating System Question Paper
Cisy 300:Computer Operating System
Course:Computer Science
Institution: Kenya Methodist University question papers
Exam Year:2012
KENYA METHODIST UNIVERSITY
END OF 2ND TRIMESTER 2012 (EVENING) EXAMINATIONS
FACULTY : COMPUTING & INFORMATICS
DEPARTMENT : COMPUTER SCIENCE & BUSINESS INFORMATION
UNIT CODE : BBIT 213/CISY 300
UNIT TITLE : OPERATING SYSTEMS
TIME : 2 HOURS
Instructions: Answer Question ONE and any other TWO Questions.
Question One: (30 Marks)
Explain the TWO main goals of an operating system.
(4 Marks)
Describe the difference between multiprogramming and time sharing. What is the main advantage of multiprogramming.
(4 Marks)
Outline the FIVE major activities of an operating system in regard to process management.
(5 Marks)
Describe the actions taken by an operating system to execute a system from when a program makes the system call till the request is executed.
(6 Marks)
What is the purpose of a command interpreter? Why is it usually separate from the kernel?
(5 Marks)
What resources are used when a thread is created? How do they differ from those used when a process is created?
(6 Marks)
Question Two: (20 Marks)
A request for a service is carried out by the Kernel which executes in Kernel mode. Explain the reasons for the mode switch that takes place in response to user requests.
(3 Marks)
Differentiate between different states a process may be in.
(5 Marks)
When an interrupt occurs, certain actions occur, certain actions occur. Describe the actions that occur and in order in which they occur and for each action explain whether it is carried out by the hardware or software.
(7 Marks)
Explain what services a process can request through each of the following system calls, giving details about the parameters required.
(5 Marks)
KILL (…..)
SIGNAL (……)
Question Three: (20 Marks)
Which of page table designs support the fastest virtual to physical address mapping. Explain. What disadvantage does that technique have:
Simple design
Direct Mapping
Combined Associative/direct mapping
(4 Marks)
Consider a page table stored in main memory and an instruction (two memory operands) which is fetched from memory by the CPU and executed. How many memory references are required in the execution of this instruction. Explain.
(4 Marks)
Consider the following page reference string 1, 2, 3, 4, 2, 1, 5, 6, 2, 1, 2, 3, 7, 6, 3, 2, 1, 2, 3,6. How many page faults would occur for the following page replacement algorithms, assuming four page frames? Remember that all frames are initially empty, so your first unique pages will all cause one fault each.
(6 Marks)
Least recently used algorithm.
Second Chance
Consider a computer that implements a pure paging system. The virtue address space consists of 512 pages of 512 words each, mapped onto physical memory of 512 page frames. Consider the following content of memory.
MM Physical Address Virtual page number
1536 8
3072 0
3584 5
4608 2
To which physical memory addresses mapped:
2624
4352
Derive your answer from first principles. (6 Marks)
Question Four: (20 Marks)
In operating systems environment, there are a number of interfaces provided by which operating system services may be accessed. Distinguish between the following interfaces.
(9 Marks)
(i) System call interface
(ii) Library interface
(iii) User interface
With the help of a suitable example, show how requests for services are made at each interface.
(3 Marks)
The following represents developments in the operating system field.
Batch monitor to multiprogramming operating systems.
Multiprogramming with fixed partitions to multiprogramming with variable partitions.
In each case explain the problems that necessitated the search for a better system. Also explain how the problem was solved by the new technique.
(8 Marks)
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