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Direct Memory Access (DMA) - Operating Systems - Old Exam, Exams of Operating Systems

Dr. Bhim Rao Ambedkar UniversityOperating Systems

These are the Old Exam of Operating Systems which includes Secrecy of Users, Passwords, Environmental Variable Path, Partitioning a Disk, Criteria for File Organisation etc. Key important points are: Direct Memory Access, Transition Diagram, Ready, Running, Ready-Suspend, Blocked-Suspend, Fetch-Execute, Machine Instructions Are Atomic, Aid Of Pseudocode, Semaphore Avoid, Busy

Typology: Exams

2012/2013

Uploaded on 03/25/2013

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Cork Institute of Technology
Page 1 of 4
Higher Certificate in Science in Computing – Award
(NFQ - Level 6)
Summer 2006
Operating Systems
(Time: 3 Hours)
Answer ANY FOUR questions.
All questions carry equal marks.
Examiners: Ms. Mairead Meagher
Ms. A. Brown
Mr. P. Rothwell.
1. (a) Given that the process states listed below exist, draw a state transition diagram
which shows all of the legal transitions between states. [3 marks]
Fully explain the meaning of each of the states. [3 marks]
Label and explain the transitions appropriately. [4 marks]
States: New, Exit, Ready, Running, Blocked, Ready-Suspend, Blocked-Suspend.
(b) Summarise the typical contents of a process control block (PCB). [4 marks]
(c) With the aid of a diagram, fully describe the ‘fetch-execute’ cycle indicating
when interrupts are handled. [4 marks]
Briefly outline the important steps in interrupt handling. [5 marks]
“Machine instructions are atomic.” Explain this statement with reference to your
diagrams. [2 mark]
[Total: 25 marks]
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Cork Institute of Technology

Higher Certificate in Science in Computing – Award

(NFQ - Level 6)

Summer 2006

Operating Systems

(Time: 3 Hours)

Answer ANY FOUR questions. All questions carry equal marks.

Examiners: Ms. Mairead Meagher Ms. A. Brown Mr. P. Rothwell.

  1. (a) Given that the process states listed below exist, draw^ a state transition diagram which shows all of the legal transitions between states. [3 marks] Fully explain the meaning of each of the states. [3 marks] Label and explain the transitions appropriately. [4 marks] States: New, Exit, Ready, Running, Blocked, Ready-Suspend, Blocked-Suspend.

(b) Summarise the typical contents of a process control block (PCB). [4 marks]

(c) With the aid of a diagram, fully describe the ‘fetch-execute’ cycle indicating when interrupts are handled. [4 marks] Briefly outline the important steps in interrupt handling. [5 marks] “Machine instructions are atomic.” Explain this statement with reference to your diagrams. [2 mark] [Total: 25 marks]

  1. (a) Several proposed software and hardware solutions to the mutual exclusion problem involve ‘busy waiting.’ Explain ‘busy waiting’ in this context. With the aid of pseudocode, fully explain how the use of a semaphore avoids the ‘busy waiting’ problem. [6 marks]

(b) Fully describe the producer/consumer problem. In the context of your description clearly explain the mutual exclusion and synchronisation problems. [9 marks]

(c) Write pseudocode to describe a solution to the bounded-buffer producer/consumer problem using semaphores. (Assume the necessary methods and classes for semaphores are defined.) [ marks] Fully explain how (^) the code you have given solves the problems of mutual exclusion and synchronisation. [5 marks] [Total: 25 marks]

  1. (a) Briefly define the notion of deadlock using an everyday example. [2 mark] List and explain the four necessary and sufficient conditions for deadlock. [4 marks]

(b) Write pseudocode to fully describe the Banker’s algorithm (and its associated ‘safety’ algorithm) for deadlock avoidance. [5 marks] Fully explain your code. [6 marks]

(c) Based on the following information, show and explain how the banker’s algorithm you described can be used to determine if the following resource request from process 1 is granted: request 1 = (0, 0, 1) [8 marks]

Process Allocation Max Available type => X Y Z X Y Z X Y Z 0 1 0 0 3 2 2 0 1 2 1 6 1 2 6 1 3 2 2 1 1 3 1 4 3 0 0 2 4 2 2

[Total: 25 marks]

  1. (a) Why is the performance of disk access seen as highly important? [2 mark] With the aid of a diagram, briefly describe the structure of a hard disk and fully explain the meaning of the terms seek time, latency, and transfer time. [4 marks]

(b) Input/Output buffering is introduced to increase the efficiency of i/o operations. With the aid of diagrams, fully explain the operation of buffering for input. [5 marks]

(c) Summarise the evolution of the input/output function in processor architecture from ‘direct processor control’ to ‘i/o processor’. [6 marks] Explain how this specialisation increases the efficiency of the CPU use. [4 marks] Briefly describe (^) the operation of the Direct Memory Access (DMA) function. [4 marks] [Total: 25 marks]