Computer Science - StudentsResource

IGCSE 0478 & O LEVEL 2210

Computer Science

TOPICAL WORKBOOK

Paper 1 | Paper 2

WITH DETAILED SOLUTIONS JUNE 2015 ? NOVEMBER 2019

Arranged and Solved by:

ALI AKRAM

A Quality Product By:

Content

Preface ........................................................................................................................................ i About the Author ...................................................................................................................... ii Acknowledgment ..................................................................................................................... iii

Section 1

Theory of Computer Science

Paper 1

Topic 1 Topic 2 Topic 3 Topic 4 Topic 5 Topic 6 Topic 7 Topic 8 Topic 9 Topic 10 Topic 11 Topic 12 Topic 13 Topic 14

Syllabus.......................................................................................................................... 1 Binary systems............................................................................................................12 Hexadecimal............................................................................................................... 23 Data storage................................................................................................................29 Data transmission...................................................................................................... 44 Internet principles of operation............................................................................... 52 Logic gates...................................................................................................................61 Computer architecture and the fetch-execute cycle..............................................77 Input Devices.............................................................................................................. 84 Output devices......................................................................................................... 103 Memory, storage devices and media.................................................................... 106 Operating systems................................................................................................... 116 High- and low-level languages and their translators.......................................... 117 Security..................................................................................................................... 122 Ethics.......................................................................................................................... 132

SOLUTION PAPER 1....................................................................................... 136

Section 2

Practical Problem-solving and Programming

Paper 2

Topic 1 Topic 2 Topic 3 Topic 4 Topic 5

Problem - solving and design..................................................................................171 Pseudocode & Flowchart........................................................................................ 188 Programming Concepts............................................................................................212 Data Structures; Arrays........................................................................................... 223 Databases.................................................................................................................. 224

SOLUTION PAPER 2....................................................................................... 240

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ALI AKRAM

Paper 1 Workbook

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ALI AKRAM

Chapter 1 Binary systems

[ M/J 2015 / P11 / Q8 a,b,c ]

1 An alarm clock is controlled by a microprocessor. It uses the 24 hour clock. The hour is represented by an 8-bit register, A, and the number of minutes is represented by another 8-bit register, B.

(a) Identify what time is represented by the following two 8-bit registers.

128 64

00

A

32 16 8

010

421

010

128 64

: 00

B

32 16 8

110

421

101

Hours . . . . . . . . . . . . .................................................................................

Writer's comment :

Refer to the time being stored in the registers in your answer to part (c).

Minutes . . . . . .......................................................................... [2]

(b) An alarm has been set for 07:30. Two 8-bit registers, C and D, are used to represent the hours and minutes of the alarm time.

In part (c) microprocessor sends signal not "information".

Show how 07:30 would be represented by these two registers:

C

D

:

Hours

Minutes [2]

(c) Describe how the microprocessor can determine when to sound the clock alarm.

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. . . . . . . . . . . . .......................................................................................................................[3]

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[ M/J 2015 / P12 / Q10 a ]

2 Letters from the alphabet are represented in a computer by the following denary (base 10) values:

A = 97

G = 103

I = 105

L = 108

N = 110

The word "A L I G N" is stored as: 97 108 105 103 110 (a) Convert each of the five values to binary. The first one has been done for you.

Letter

Denary value

A (97): 0 1 1 0 0 0 0 1

L (108):

I (105):

G (103):

N (110):

[2]

ALI AKRAM

[ M/J 2016 / P11 / Q7]

3 Each seat on a flight is uniquely identified on an LCD above the seat. For example, seat 035C is shown as:

The first three characters are digits that represent the row. The fourth character is the seat position in that row. This is a single letter, A to F, that is stored as a hexadecimal value.

Each of the four display characters can be stored in a 4-bit register. For example, 0 and C would be represented as:

8421

0: 0 0 0 0 C: 1 1 0 0

(a) Show how the 4-bit registers would store the remaining two characters, 3 and 5.

3

5

(b) Identify which seat is stored in the following 4-bit registers.

0001 1001 0100 1110

Writer's comment :

[2] Profess the skill of conversion to and from hexadecimal digits espacially, A (10),B (11), C (12), D (13), E (14), F (15).

[2]

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[ M/J 2016 / P12 / Q3]

4 (a) Convert the following hexadecimal number into 12-bit binary:

4 A F

ALI AKRAM

[3]

(b) The 2016 Olympic Games will be held in Rio de Janeiro. A timer that counts down to the opening of the Games is shown on a microprocessor-controlled display.

The number of hours, minutes and seconds until the Games open are held in three 8-bit

registers.

Writer's comment :

The present register values are:

01101001 00100000

105 hours 32 minutes

In part (b) (i) count down the the number of seconds and then see if effects minutes. Same goes with minutes to hour.

00010100

20 seconds

The timer will count down in seconds. (i) Show the values in each 8-bit register 30 seconds after the time shown above:

hours

minutes

seconds [3]

(ii) Write the hexadecimal value of the minutes register from part (b)(i). . . . . . . . . . . . . . . . .........................................................................................................[1]

[ O/N 2016 / P12 / Q5]

5 A computer uses an 8-bit register. The 8-bit register contains binary integers. (a) Write the denary (base 10) value represented by:

128

64

32

16

8

4

2

1

01110000

..............................................................................................................................................[1]

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Chapter 2 Hexadecimal

[ O/N 2015 / P12 / Q4 ]

1 (a) (i) Convert the following two hexadecimal numbers into binary: F A 7 D 3 E

F A 7

ALI AKRAM

D 3 E [4]

(ii) Now perform the AND (logic) operation on each corresponding pair of binary bits in the two numbers from part (i).

[2]

(iii) Convert your answer in part (ii) into hexadecimal.

..........................................................................................................................................

.......................................................................................................................................... [2]

(b) (i) The following code shows HTML `tag' pairs on either side of the text stating the colour that each creates.

RED

GREEN

BLUE

YELLOW

MAGENTA

CYAN

Yellow is a combination of red and green, magenta a combination of red and blue and cyan a combination of green and blue.

State what 6-digit hexadecimal values should replace X, Y and Z in the above code.

X . . . . . . ............................................................................................................................

Y . . . . . . ............................................................................................................................

Z . . . . . . ............................................................................................................................ [3]

(ii) Describe how other colours, such as a darker shade of blue, are created.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... [2]

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(c) 1A ? 16 ? C5 ? 22 ? FF ? FF is an example of a MAC address.

(i) Identify what the first six and last six hexadecimal digits represent.

First six digits . ..................................................................................................................

..........................................................................................................................................

..........................................................................................................................................

Last six digits . ...................................................................................................................

. . . . ....................................................................................................................................

. . . . . . . . . . . . . . ............................................................................................................... [2]

(ii) State why MAC addresses are used.

..........................................................................................................................................

. . . . . . . . . . . . . . . ............................................................................................................. [1]

ALI AKRAM

[ M/J 2016 / P11 / Q2 ]

Writer's comment :

2 Hexadecimal codes are used in MAC addresses.

Keep into account that

(a) State what is meant by the term MAC.

the two halves of MAC address represent

. . . . . . . . ................................................................................................................................[1] dif-ferent aspects. The

first half represents

(b) Explain what the hexadecimal code in a MAC address represents.

manufacturer's

identification and that . . . . . . . ...................................................................................................................................... the second half rep-

. . . . . . . ...................................................................................................................................... resents

the serial

number of the device.

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. . . . . . . . ................................................................................................................................[3]

[ M/J 2017 / P11 / Q1 ]

3 The memory of a computer contains data and instructions in binary. The following instruction is stored in a location of the memory. 0010100111111100 (a) Convert the instruction into hexadecimal. . . . .............................................................................................................................................. . . . .............................................................................................................................................. . . . . . ......................................................................................................................................[2]

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