University
Faculty McGill of Engineering
FINAL EXAMINATION
FALL 2006 (DECEMBER 2005)
VERSION A
COMPUTER ENGINEERING
ECSE-322A
6 December 2005, 0900 - 1200
Examiner: Professor D.A.Lowther
Co-Examiner: Professor T.Arbel
Signature:
Signature:
STUDENT NAME AND SIGNATURE
MCGILL I.D. NUMBER
INSTRUCTIONS:
This is a CLOSED BOOK examination. Only one (1) hand-written (not photo-copied) double sided CRIB SHEET
on letter size (8.5 by 11 inch) paper permitted.
This is a MULTIPLE CHOICE examination. It will be subject to the Harp Hogan Program. This is a program that
will be run by the Computing Centre to check for the possibility of cheating.
MARK YOUR ANSWERS TO THE MULTIPLE CHOICE QUESTIONS ON THE ENCLOSED
COMPUTER SHEET USING PENCIL ONLY. Each question is worth 1 mark, a wrong answer will receive 0.
Space is provided on the exam in which to answer the short answer questions (46 to 49). DO NOT USE ANY
OTHER EXAM BOOKS FOR ANSWERS TO BE MARKED.
You are permitted REGULAR AND TRANSLATION dictionaries.
FACULTY STANDARD CALCULATOR permitted ONLY.
Student answers in the multiple choice section will be subject to analysis by the McGill Exam Security Computer
Monitoring Program in order to identify unusually similar answer patterns.
This examination consists of two parts; part 1 consists of 45 multiple choice questions, part 2 consists of a set of 4
short answer questions OF WHICH YOU SHOULD ATTEMPT ONLY 3. The examination consists of a total of __
pages including this cover page. Please ensure that you have a complete examination paper BEFORE starting.
Please sign this paper at the top of this page, write your name legibly, and read the instructions above. Initial
each page of the exam paper in case the sheets should get separated.
THIS EXAMINATION PAPER MUST BE RETURNED.
LIST QUESTIONS ATTEMPTED IN PART 2 HERE:
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TEST QUESTIONS
PART 1 - This part consists of 45 multiple choice questions. Indicate the correct answer
to each question on the computer readable sheets provided.
1. In a particular sorting process the first iteration places 1 data item in the correct
position; the second places a further 2; by the fourth pass 15 items are correctly placed.
The time complexity of this process is
(a) O (constant)
(b) O (log2N)
(c) O(N)
(d) O (Nlog2 N)
(e) O(N2)
2. In a tree data structure a leaf of the tree is identified by
(a) it is the only node containing data
(b) it does not have two children
(c) all the children are nulls
(d) some of the children are nulls
(e) none of the above
3. An inorder traversal of a binary tree structure visits the nodes in the sequence
(a) root, left, right
(b) root, right, left
(c) right root, left
(d) left, root, right
(e) left. right, root
4. In a hashed data structure of size M and a data set of size N (N<m) the maximum
number of collisions that could occur is
(a) O(M)
(b) O(M2)
(c) O(MN)
(d) O(N)
(e) O(N2).
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5. Vectoring is often used in multi-dimensional arrays because
(a) It provides a way to save memory
(b) It reduces the time needed to access an array element
(c) It removes the need to perform an address calculation
(d) It simplifies the calculation of a vector-vector product
(e) It is never used.
6. A queue is often referred to as a
(a) Last in first out structure
(b) First in last out structure
(c) First in first out structure
(d) Last in mort important out structure
(e) Single in multiple out structure.
7. The effect of limiting the number of bits used to represent the exponent of a floating
point number is to
(a) limit the resolution with which numbers can be represented
(b) limit the dynamic range over which numbers can be represented
(c) remove the ability to represent negative exponents
(d) remove the ability to represent negative number
(e) allow the use of hidden bit normalization.
8. The effect of limiting the number of bits used to represent the mantissa of a floating
point number is to
(a) limit the resolution with which numbers can be represented
(b) limit the dynamic range over which numbers can be represented
(c) remove the ability to represent negative exponents
(d) remove the ability to represent negative number
(e) allow the use of hidden bit normalization.
9. Which of the following does NOT need to be represented by a dynamic data structure?
(a) a library
(b) a book
(c) a bus line up
(d) a pile of dishes
(e) a list of the students in ECE at McGill.
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10. The Read Only Memory in the printer discussed in class is used to
(a)
(b)
(c)
(d)
(e)
Store characters to be printed as they are received
Convert characters to ASCII codes
Convert ASCII Codes to control signals for the printer
Remove the need for hardwired logic in the printer
Handle the serial line communications protocol.
11. The Address Decoder on an interface is used to
(a)
(b)
(c)
(d)
(e)
convert the address on the bus to a location in memory
store the address in memory for a DMA transfer
provide a clock signal for incrementing the byte count in a DMA transfer
provide a load signal for the Device Data Register
provide control information to the device.
12. An Interrupt Service Routine is BEST described as
(a)
(b)
(c)
(d)
An additional control line on the bus to allow an interface to signal to the CPU
A piece of software stored at a specific location in the memory of a processor
A subroutine accessed at the end of a fetch and execute cycle in the CPU
A subroutine which controls the movement of data to and from an interface and is
initiated by a signal on the bus.
(e) A routine in the operating system designed to move data to and from an interface.
13. The XON/XOFF protocol was developed to
(a)
(b)
(c)
(d)
(e)
Provide synchronization between two ends of a serial line communication system
Prevent buffer overflow happening in a peripheral device
Maximize the speed at which a graphics device can operate
Reduce the overhead in serial line data transmission
Minimize the number of connections needed for an RS-232 communication
system.
14. The serial line character display discussed in class is faster than a bit mapped raster
display because
(a) It only displays characters
(b) It does not need to use a raster display system
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(c) It uses hardwired digital logic
(d) It is not directly connected to the computer bus
(e) It uses a dedicated CPU.
15. Which of the following devices provides an absolute position?
(a)
(b)
(c)
(d)
(e)
Glide pad
Track ball
Joystick
Pen
They all do
16. The main reason for implementing DMA in a computer system is
(a)
(b)
(c)
(d)
(e)
To free off the CPU to do other work
To simplify the writing of interrupt service routines
To remove the need for a buffer on the device interface
To reduce the number of logic circuits needed in the interface.
To speed up the transfer of data between an interface and the main memory.
17. Which of the following signals is NOT embedded in a Composite Video Signal?
(a)
(b)
(c)
(d)
(e)
Clock
Horizontal synchronization
Vertical synchonization
Vertical blanking period
Image (video) data.
18. In Cycle Stealing DMA
(a)
(b)
(c)
(d)
(e)
The device takes the bus only when it has data to transfer
The device takes and holds the bus during the entire DMA process
The CPU only grants the bus to the device when it does not need it
The BUS GRANT line is never set
The CPU has to enable BUS REQUEST before each DMA transfer.
19. Which of the following is NOT a characteristic of a magnetic tape?
(a) It is removable
(b) It is non-volatile
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(c) It provides direct access to data
(d) The cost/byte is extremely low
(e) It can provide a large amount of secondary storage.
20. A floppy disk rotates slower than a hard disk because
(a) It is likely to stretch due to the centrifugal forces at high speed and thus the data
would not be readable
(b) If it is rotated faster, the data rate would be too high for the interface
(c) DMA cannot be implemented for its interface
(d) The friction between the head and the disk would destroy both
(e) Too much power would be needed to rotate it faster.
21. Which of the following pieces of information is NOT needed for find data on a floppy
disk?
(a)
(b)
(c)
(d)
(e)
Platter
Surface
Track
Sector
All are needed.
22. The maximum throughput of a bus is
(a)
(b)
(c)
(d)
(e)
dependent on the number of interfaces connected to it
dependent on the address space of the computer
decreases as more devices are added to it
related to the bus protocol implemented
related to the data transfer rate of the fastest device on the bus.
23. In a semi-synchronous protocol
(a)
(b)
(c)
(d)
(e)
there is no clock signal
devices can respond on any clock edge
a device may take several clock cycles to respond
a device must respond within one clock cycle
a devices responds to changes in control signals
24. Which of the following control signals is NOT needed to implement an asynchronous
protocol?
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(a)
(b)
(c)
(d)
(e)
clock
address strobe
data strobe
read
write
25. A Non-interlocked protocol is one in which
(a)
(b)
(c)
(d)
Signals can be read on any edge of the clock signal
Devices on the bus check all changes in state of the control lines
Devices only check and respond to activation of control lines
Devices do not wait for a strobe (synchronization) signal before reading the data
or address lines
(e) Devices do not have to wait for the Bus Grant signal before placing data on the
bus.
26. The MAIN role of an Arbiter in allocating the bus is to
(a)
(b)
(c)
(d)
(e)
Allow only one device to access the bus at a time
Allow only one device to control the bus at a time
Ensure that the highest priority device always gets the bus
Provide a prioritized but fair access to the bus
Ensure that a device in control of the bus cannot be interrupted.
27. Which of the following control signals is NOT used in the bus arbitration process?
(a)
(b)
(c)
(d)
(e)
Bus Request
Bus Grant
Bus Busy
Bus Release
Bus Acknowledge
28. In the event that the bus is being used and a higher priority device has requested it,
which one of the following signals would be activated?
(a)
(b)
(c)
(d)
(e)
Bus Request
Bus Grant
Bus Busy
Bus Release
Bus Acknowledge
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29. In an Asynchronous Protocol performing a read operation, when would the Slave
Synchronization signal be set?
(a)
(b)
(c)
(d)
(e)
As soon as the data is stable
As soon as the address is stable
As soon as the master synchronization signal is set
As soon as the read signal is set
It would not be set since it is not needed in this operation.
30. Which of the following best describes a process?
(a)
(b)
(c)
(d)
(e)
A user program
A routine in the operating system
A device driver
A piece of software that performs an action and can be controlled
A piece of software that accesses a resource.
31. In the context of an operating system, which of the following is the best description of
concurrency?
(a)
(b)
(c)
(d)
(e)
Allowing several hardware devices to operate simultaneously
Allowing several processes to be active simultaneously
Allowing several processors to access memory simultaneously
Allowing one device to request a resource while another is using it
Allowing several users to access the processor simultaneously.
32. When a process has requested a resource and the resource is not available, the
process is said to be
(a)
(b)
(c)
(d)
(e)
running
ready
sleeping
blocked
completed
33. A privileged instruction is one which
(a) Accesses an non-shareable resource
(b) Can only be executed in kernel mode
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(c) Can only be executed by processes having a high enough priority
(d) Can be executed when the system is deadlocked
(e) Is used during process swapping.
34. A semaphore is
(a)
(b)
(c)
(d)
(e)
A signal used by a resource to indicate that it is busy
A software interrupt used to request service
A non-negative integer used for control
A variable whose value is incremented by a wait operation
A small piece if software used to synchronize processes.
35. Which of the following is NOT a condition for deadlock?
(a)
(b)
(c)
(d)
(e)
All the resources are non-shareable
All processes need one more resource
All processes hold onto resources while waiting for new ones
Resources cannot be relinquished when they are being used
Each process holds resources currently being requested by the next process in the
chain.
36. The volatile environment of a process is
(a)
(b)
(c)
(d)
The main memory used by the process when executing
The devices, other than disks and tapes, that it uses when executing
The set of instructions being executed by a process
A subset of modifiable shared resources used by the process, e.g. registers and
program counter
(e) The set of non-shareable resources used by the process and protected by the
operating system.
37. The directory on a device is
(a)
(b)
(c)
(d)
(e)
The area where files are stored on the device
The area containing the addresses of files on the device
The area on the device containing information about the device formatting
The area on the device used for decoding file addresses
The area on the device containing boot information for the operating system.
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38. The head to disk spacing in a CD-ROM is of the range of
(a)
(b)
(c)
(d)
(e)
1 to 9 micro-inches
10 to 99 micro-inches
100 to 999 micro-inches
1000 to 9999 micro-inches
10,000 to 99,999 micro-inches
39. The physical law that states that a current flowing in a conductor will create a
magnetic field is known as
(a)
(b)
(c)
(d)
(e)
Amperes Law
Faradays Law
Ohms Law
The Kerr Effect
Moores Law
40. Burst feeding is a system by which
(a) Graphics data is loaded into a frame buffer in the vertical blanking period
(b) Many bytes of data are transmitted to the buffer on a device through a single
interrupt
(c) A device interface moves data directly to or from memory
(d) The need for a buffer on a device is removed
(e) Several bytes of data can be sent to several devices simultaneously.
41. The most common (and important) disadvantage of a linked list structure for storing
files on disk is
(a)
(b)
(c)
(d)
(e)
That a file can be spread out over the entire disk leading to long access times
That a large number of unusable spaces are created on the disk as files are edited
That the directory MUST be stored in random access memory
That a file can be completely lost if a single link is destroyed
That files must be interleaved on the disk.
42. Tri-state buffers are used to place address and data signals on the bus because
(a)
(b)
(c)
(d)
They a have smaller logic delay than normal buffers
They allow all devices to read data from the bus simultaneously
They allow write access to the bus to be controlled by the bus arbiter
They simplify the design of cycle stealing direct memory access
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(e) They can be used to auto-increment the address and word count.
43. When a computer is first turned on, it executes a bootstrap to begin loading the
operating system. The first part of the bootstrap is found
(a)
(b)
(c)
(d)
(e)
In the random access memory
In the first sector of the first track of a floppy disk
In the first sector of the first track of a hard disk
In a read only memory
It is built into the processor.
44. Sector Interleaving is a technique by which
(a)
(b)
(c)
(d)
(e)
The number of heads needed on a disk drive is minimized
More information can be stored on a given disk
The fracturing of a disk is minimized
The interface/disk drive interaction is optimized
DMA transfers are simplified.
45. The address space of a computer is determined by
(a)
(b)
(c)
(d)
(e)
The amount of RAM installed
The word width of the processor
The number of address lines
The number of data lines on the bus
The operating system
PART 2 of this exam starts on the next page. Please turn over the page and begin Part 2
NOW!
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PART 2 - This part consists of 4 short answer questions. YOU SHOULD ANSWER ONLY
3 (THREE) OF THE QUESTIONS - IF YOU ANSWER 4, ONLY 3 WILL BE MARKED.
Each question is worth 12 marks (Each question consists of 4 sections). Write your
answers to the question in the space provided on this exam paper. Do not use extra paper
- any answers written outside of the allowed space will not be marked.
46. (a) Give brief descriptions of the following terms (each is worth 1 mark):
(i)
Polled interrupt system:
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(ii)
Device Data Register:
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(iii)
Cursor:
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(b) A computer is to be connected to a printer via a serial line consisting of three
wires one of which is a common signal ground.
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(ii)
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Describe (either by words or a diagram) how reliable transmission of ASCII
characters over this link could be achieved assuming that both ends of the
system have the same clock speed. (2 marks)
If the printer is equipped with a memory buffer, describe a process which
might be used to avoid buffer overflow. Give this process as a set of steps. (1
mark)
(c) A printer buffer is designed for a printer which can print c characters per second.
A page of text consists, on average, of d characters and the connection between the
interface and the printer can run at a maximum speed of t bytes per second.
Characters are transmitted on a serial link using ASCII coding and come in bursts, i.e.
a page is transmitted at the maximum rate of the link and then the transmission will
pause until the next page is ready..
(i)
What is the maximum number of pages per hour that the printer can expect to
receive from the computer? (1 mark)
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(ii)
What is the minimum buffer size that will be needed (if t is greater than c) and
what is the limit on the number of pages to be printed per hour , p, if this
buffer is not to overflow? (1 mark)
(iii)
Sketch a graph showing the buffer size as a function of the number of pages
per hour assuming that the only limit to the number of pages to be printed per
hour is set by the transmission speed. Assume that the printer will work for a
maximum period of one hour. (1 mark)
(d) The following sequence of operations describes an interrupt process. Draw the timing
diagram for the process and design the logic circuit that will implement it.
Device has data ready to send
Interrupts are enabled
An interrupt is generated
An interrupt acknowledge signal is sent back
The Interrupt Service Routine address is placed on the bus
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(ii)
Timing Diagram: (1.5 marks)
(iii)
Circuit: (1.5 marks)
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47. (a) Explain the following terms (maximum one sentence for each) (1 mark each)
(i)
Logic Delay:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(ii)
Capacitative Delay:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(iii)
Transitive Delay:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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(b) (i) Draw the timing diagram for a write operation in the semi-synchronous bus
protocol. (2 marks)
(ii)
Give one advantage of a semi-synchronous protocol when compared to a
synchronous protocol (0.5 marks)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(iii)
Give one disadvantage of the semi-synchronous protocol when compared to
an asynchronous protocol (0.5 marks)
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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(c) An interlocked asynchronous bus using only Master and Slave Synchronization
signals has a set up time for both the address and data by the Master of t nanoseconds, the
master (or slave) takes two gate delays (g nanoseconds per delay) to respond to a signal;
the propagation speed of signals along the bus is v meters/nanosecond and the bus is L
meters long. If the data path is 4 bytes wide, derive an expression for the maximum data
transfer rate, R, (in bytes per second) that can be achieved for a WRITE operation. (3
marks)
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(d) The diagram below relates to a sequence of operations on an arbitration bus.
Signal 1
Signal 2
Signal 3
Signal 4
Signal 5
Signal 6
(i)
Describe the operations that are taking place (1 mark)
_____________________________________________________________________
_____________________________________________________________________
(ii)
Name the signals in the diagram (2 marks)
Signal 1: ____________________________________________________________
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Signal 2: ____________________________________________________________
Signal 3: ____________________________________________________________
Signal 4: ____________________________________________________________
Signal 5: ____________________________________________________________
Signal 6: ____________________________________________________________
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48. (a) Explain what is meant by each of the following terms. (1 mark each)
(i)
Sector:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(ii)
Cylinder:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(iii)
Seek Time:
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
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(b) (i) Explain why Sector Interleaving is often implemented on a hard disk. (1 mark)
______________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
(ii)
It is desired to find an optimum sector interleave factor for a particular
disk/interface pair. Describe, using pseudo-code or a flow chart, an algorithm
which would allow this to be determined (2 marks).
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(c) A hard disk drive is designed to have p platters and to have t tracks per inch. The
outer radius of the disk is R inches. Data is fed to the disk at B bytes per second. The
maximum areal recording density is D bits per square inch.
(i)
What should be the radius of the innermost track if the amount of data to be
stored on the disk is to be maximized? (1 mark)
(ii)
If the inner radius is set to provide the maximum storage capability, what
should the rotational speed of the disk be to be able to accept data at the rate
the interface is sending it? (Assume the seek time is zero). (0.5 marks)
(iii)
What would happen to the total data stored on the disk and the disk
performance if the rotational speed was increased above the speed from part
(ii)? (0.5 marks)
_____________________________________________________________________
_____________________________________________________________________
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If the disk speed was reduced by 20% from that in part (ii) but all the other
parameters stayed constant? What is the total amount of data that can be
stored on the disk if one surface is used for timing?(1 mark)
As the disk slows down but the data rate stays the same, the physical size of the bits
on the disk (at the innermost recorded track) reduces. This cannot happen in the
model considered in part (ii) since the inner track bits are already at the minimum size
for this disk. Assuming all the parameters stay the same, the inner recording radius
will have to increase:
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(d) Describe, either in the form of a flowchart or as a sequence of operations, the steps
taken during a data transfer using a cycle stealing Direct Memory Access system. Start
from the point at which it is determined that input is needed from a device and end when
all the data has been transferred. In particular, indicate the changes in state of the control
lines.
The diagram should be in the from of two columns one for the CPU, the other for the
interface and the communication between the two should be indicated.(3 marks)
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49. (a) (i) Give four functions of the Nucleus (Kernel) of an Operating System. (0.5
marks each)
(1) __________________________________________________________________
(2) __________________________________________________________________
(3) __________________________________________________________________
(4) __________________________________________________________________
(ii) Name the two parts an Operating System is often divided into. (0.5 marks each)
(1) _________________________________________________________________
(2) _________________________________________________________________
(b) There are three main problems which can occur as a result of Concurrency. Name
each of these and give a brief explanation of the problem (maximum 20 words) (1 mark
each)
Problem 1: ______________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
Problem 2: ______________________________________________________________
_______________________________________________________________________
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_______________________________________________________________________
Problem 3: ______________________________________________________________
_______________________________________________________________________
_______________________________________________________________________
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(c) (i) The diagram below shows the state transitions of a process. Fill in all the blank
states indicated in the figure. ( 2 marks)
Blocked
(ii) Explain how a process may become blocked and how it can move out of this state.
A Process becomes blocked when____________________________________________
_______________________________________________________________________
___________________________________________________________(0.5 marks)
A Process can move out of a blocked state when________________________________
_______________________________________________________________________
___________________________________________________________(0.5 marks)
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(d) (i) Three (3) processes share four (4) resources which can be reserved and released
only one at a time. Each process needs a maximum of two (2) resources to be able to
complete (it does not matter which ones). Explain why deadlock occurs and show that it
cannot occur in this system. (2 marks)
(ii) In any operating system one process always exists. Name the process and explain
why it can never be in a blocked state.
Process: __________________________________________________(0.5 marks)
Explanation: _______________________________________________________
________________________________________________________(0.5 marks)
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