Introduction To Computers And Principles Of Operating Systems July 2007

Exam Year:2007

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1. (a) State four objectives of process scheduling in a computer system.(4marks)
(b) Discuss the following process scheduling algorithms
(i) Short job First (SJF).
(ii) Shortest job Remaining Next (SJRN)(6marks)
(c)Table 1 shows four process and their CPU burst times.
Process————– Arrival time———-CPU Burst
A——————– 0———————- 20
B——————– 1———————- 5
C——————– 2———————- 15
D——————– 3———————- 10
(i) Illustrate execution of the process using the round robin scheduling algorithm given that the time slice is 4 units.(4marks)
(ii) Illustrate the execution of the process using the First come first served scheduling algorithm.(2marks)
(iii) Evaluate the CPU performance based on the results obtained in (i) and (ii).(4marks)

2.(a) A large organization with a large warehouse would like to buy some computers for its staff members.As a computer expert,advicse on the most suitable type of computers to be purchased for the following personnel:(justify your answer in each case).
(i) Secretaries.
(ii) Market-research executives.
(iii)A stores manager in charge of physically verifying stocks in the warehouse.
(iv) The company director for scheduling all his appointments and what-to-do-lists.
(v) A database administrator for storing all the data of the organization.(5marks)
(b) An entrepreneur would like to start a cybercafé that will include a business unit where advertisements, brochures, letters and documents can be produced. The cybercafé will also support video conferencing for all its clients.
(i) Explain five hardware devices that would be required for the successful implementation of the cybercafé.(5marks)
(ii) Identify four types of software that would be required in the cybercafé giving a suitable example in each case.(4marks)
(iii) Explain a suitable security mechanism that could be used to prevent network intrusion to the cybercafé.(2marks)
(c)A large company is planning to network its computers with a provision for centralized access to its data resources. Justifying your answer, identify two computer personnel who would be required to achieve the company’s objectives.(4marks)

3.(a) Explain four negative impacts of internet technology in an organization.(4marks)
(b) A company would like to install a reliable LAN with minimal cabling. The medium access mechanism to be adopted will ensure that only one computer transmits data at any given time successfully. With the aid of a sketch diagram, describe a suitable topology that could be used.(6marks)
(c)A school would like to buy computers, Explain three types of operating systems that the school can choose from, giving an example in each case.(6marks)
(d) Write the MS-DOS commands to perform the following tasks :
(i) Create a lotus 1 directory.
(ii) Change to the lotus 1 directory.
(iv) Copy lotus 1 program stored on a hard disk to a diskette.
(v) Return to the root directory.(4marks)

4. (a) Differentiate between device drivers and device controllers.(4marks)
(b) Input and output devices cannot be able to keep pace with the processor so that peaks and troughs in 1/0 data rates needs to be smoothed to keep the processor working at an optimum speed.
(i) Identify two techniques that can be used to improve on performance. (2marks)
(ii) Describe the techniques identified in (b) (i). (4marks)
(c)A disk has the following cylinder requests: 2, 15, 30,9,16 and 10 in that order. Given that the disk arm is at position 14, describe the head movement using the following scheduling algorithms.
(i) FCFS.
(ii) Shortest Service Time First.
(iii) SCAN.(6marks)
(d) Describe four registers that are required during an interrupt. (4marks)

5. (a) With the aid of a diagram, describe the Five-state process model.(8marks).
(b) (i) Distinguish between semaphores and monitors as used in operating systems.(4marks)
(ii) Explain how deadlocks can be avoided using semaphores.(4marks)
(c)Describe the following terms as used in operating systems :
(i) Race condition.
(ii) Critical region.(4marks)

6.(a) A student wanted to install an application program that was stored in a compact disk which did not have the Auto Run feature.Describe the procedure he would follow to install the program.(4marks)
(b) As a copy typist was working on her computer,the mouse failed before she could complete her assignement.State the keyboard keys she would use to perform the following tasks:
(i) Move the cursor to the end of the line
(ii) Place data from a clipboard to a document.
(iv) Terminate an application that is not responding.(3marks)
(c)Explain two factors that should be considered when buying a new mouse to replace a faulty one.(2marks)
(d) A doctor recently acquired a new computer system.
(i) State five safety guidelines that he should follow in order to avoid computer related injuries.(5marks)
(ii) List six measures that the doctor should take to ensure that his computer is free from viruses.(6marks)

7.(a) Direct Memory Access is used to enhance the performance of a computer.Using a diagram,describe how this is achieved in an output/input operation.(5marks)
(b) Distinguish between paging and segmentation as applied in memory management.(4marks)
(c) A computer system has two types of clocks.
(i) State five roles of the clock software in a computer system.(5marks)
(ii) Describe the two modes of operation of a hardware clock.(6marks)

8.(a) Distinguish between a file and a root directory.(4marks)
(b) A teacher needs a file to store students information. The file will be updated every term. The teacher will have only access rights to write. Describe four operations that can be performed on the file.(4marks)
(c)Distinguish between absolute and relative paths names as applied in operating systems.(4marks)
(d) Describe four protection mechanisms that are used by operating systems to ensure security.(8marks)

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