O Level & IGCSE Computer Science

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O Level & IGCSE

Computer Science

IQ Data Representation R Workbook

AHBA9Z20T4A594 Compiled by SH0300Shahbaz Tariq

Contents

Syllabus content & assessment at a glance ............................................................................................3 1.1 Data representation..................................................................................................................................5

Denary (Decimal) Number System:- .....................................................................................................5 1.1.1 Binary Number System:- ...............................................................................................................6 1.1.2 Hexadecimal Number System:- ...................................................................................................9

Examination Questions .................................................................................................................... 16

IQ 1.1.3 Data storage................................................................................................................................. 23 Examination Questions: ................................................................................................................... 26 R Error Detection and Correction ....................................................................................................... 28 Examination Questions: ................................................................................................................... 29

SH0A3H0B0 A9Z20T4A594 Marking Schemes................................................................................................................................. 51

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Syllabus content & assessment at a glance

Sections

Topics

Section 1

Theory of Computer Science

1.1 Data representation

1.1.1 Binary systems

BAZ 0T4A5R9I4Q Section 2

1.1.2 Hexadecimal 1.1.3 Data storage 1.2 Communication and Internet technologies 1.2.1 Data transmission 1.2.2 Security aspects 1.2.3 Internet principles of operation 1.3 Hardware and software 1.3.1 Logic gates 1.3.2Computer architecture and the fetch-execute cycle 1.3.3 Input devices 1.3.4 Output devices 1.3.5 Memory, storage devices and media 1.3.6 Operating systems 1.3.7High- and low-level languages and their translators 1.4 Security 1.5 Ethics Practical Problem-solving and Programming 2.1 Algorithm design and problem-solving 2.1.1 Problemsolving and design 2.1.2 Pseudocode and flowcharts 2.2 Programming 2.2.1 Programming concepts 2.2.2 Data structures; arrays 2.3 Databases

AH 92 Paper 1 Theory

1 hour 45 minutes

This written paper contains short-answer and structured questions. All

questions are compulsory.

H 0 No calculators are permitted in this paper.

75 marks

Externally assessed.

Paper 2 Problem-solving and Programming 1 hour 45 minutes

S 0 This written paper contains short-answer and structured questions. All

questions are compulsory. 20 of the marks for this paper are from questions

3 set on the pre-release material. 1

No calculators are permitted in this paper.

50 marks

0Externally assessed.

Weighting 60%

40%

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Paper 1 SH0A3H0B0A9Z20T4A5R9I4Q Theory of Computer Science

Page 4

1.1 Data representation

Candidates should be able to: 1.1.1 Binary systems ? recognise the use of binary numbers in computer systems ? convert denary numbers into binary and binary numbers into denary ? show understanding of the concept of a byte and how the byte is used to measure memory size ? use binary in computer registers for a given application (such as in robotics, digital

Q instruments and counting systems)

1.1.2 Hexadecimal

I ? represent integers as hexadecimal numbers

? show understanding of the reasons for choosing hexadecimal to represent numbers ? convert positive hexadecimal integers to and from denary

R ? convert positive hexadecimal integers to and from binary

? represent numbers stored in registers and main memory as hexadecimal ? identify current uses of hexadecimal numbers in computing, such as defining

A colours in Hypertext Markup Language (HTML), Media Access Control (MAC)

addresses, assembly languages and machine code, debugging 1.1.3 Data storage

T 4 ? show understanding that sound (music), pictures, video, text and numbers are

stored in different formats

9 ? identify and describe methods of error detection and correction, such as parity

checks, check digits, checksums and Automatic Repeat reQuests (ARQ)

Z ? show understanding of the concept of Musical Instrument Digital Interface (MIDI) 5 files, jpeg files, MP3 and MP4 files

? show understanding of the principles of data compression (lossless and lossy

A compression algorithms) applied to music/video, photos and text files B 04 "The system of counting and calculating is called number system."

Number system is based on some characters called digits. The number of digits is

H 2 known as base or radix of the number system. For example binary number system uses

two characters 0 and 1 and its base is 2.

A 9 Computer uses following four numbers:

i) Denary (Decimal) number system ii) Binary number system

H 0 iii) Hexadecimal number system

Denary (Decimal) Number System:-

S 0 "The number system which is based on 10 characters from 0 to 9 is called denary (decimal) system." 3It is the most common number system. The digits of decimal system are 0, 1, 2, 3, 4, 5, 6, 7, 8, and 9. The value of each digit in a figure depends upon its weight. The 0weights are based on power of 10.

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