Computer Science course notes
AQA GCSE Computer Science (8525) - Aaryen Labana
Contents
1 - Fundamentals of algorithms...................................................................................................................4
Linear Search...........................................................................................................................................5
Binary Search...........................................................................................................................................5
Bubble Sort..............................................................................................................................................6
Merge Sort...............................................................................................................................................6
2 – Programming.........................................................................................................................................7
Data Types...............................................................................................................................................7
String Handling Operations......................................................................................................................7
Arithmetic Operations.............................................................................................................................8
Selection..................................................................................................................................................9
Iteration...................................................................................................................................................9
Nested Loop.............................................................................................................................................9
Infinite loops............................................................................................................................................9
Structure of indefinite and definite iteration.........................................................................................10
Records..................................................................................................................................................10
Dictionaries............................................................................................................................................10
Difference between Functions and Procedures.....................................................................................11
Subroutines............................................................................................................................................11
Flowcharts.............................................................................................................................................11
Pseudocode...........................................................................................................................................12
Trace Tables...........................................................................................................................................13
3 – Fundamentals of data representation.................................................................................................13
Units, binary and hexadecimal numbers................................................................................................13
Binary.................................................................................................................................................13
Hexadecimal Numbers.......................................................................................................................14
Binary Arithmetic...............................................................................................................................15
Overflow errors..................................................................................................................................16
Binary Shift.........................................................................................................................................16
Representing Text using binary..............................................................................................................17
1 of 74
, Ascii....................................................................................................................................................17
Character Encoding............................................................................................................................18
Unicode..............................................................................................................................................18
Representing images.............................................................................................................................19
Converting Binary data into a Bitmap and back.................................................................................20
Representing Sound..............................................................................................................................20
Compression..........................................................................................................................................22
Compression in images using RLE......................................................................................................23
Compressing text with Huffman trees...............................................................................................24
4 – Computer systems...............................................................................................................................27
Types of computer systems...................................................................................................................27
Boolean Logic.........................................................................................................................................29
Computer Memory................................................................................................................................30
Secondary Storage.................................................................................................................................32
Cloud storage.........................................................................................................................................37
CPU........................................................................................................................................................38
Software................................................................................................................................................42
Language Translators.............................................................................................................................45
5 – Fundamentals of computer networks..................................................................................................48
What Are Computer Networks?............................................................................................................48
Types of Network...................................................................................................................................48
Wired and Wireless Networks...............................................................................................................49
Network Cables......................................................................................................................................50
Wired Networks.....................................................................................................................................51
Wireless Networks.................................................................................................................................51
Wired Network Topologies....................................................................................................................53
Communicating across networks...........................................................................................................54
Network Protocols.................................................................................................................................56
Network Security...................................................................................................................................58
6 – Cyber security......................................................................................................................................62
Penetration Testing...............................................................................................................................62
Social Engineering..................................................................................................................................63
Protection Against Pharming.................................................................................................................64
2 of 74
, Protecting Against Social Engineering....................................................................................................64
Malware.................................................................................................................................................64
Protecting against Malware...................................................................................................................65
Detection and Prevention of Cyber Security Threats.............................................................................66
7 – Relational databases and Structured Query Language (SQL)...............................................................67
Relational Databases.............................................................................................................................67
Data Redundancy and Inconsistency.....................................................................................................70
Structured Query Language (SQL)..........................................................................................................71
8 – Ethical, legal and environmental impacts of technology on wider society, including issues of privacy
................................................................................................................................................................... 73
Data Protection Act:..............................................................................................................................73
Technologies..........................................................................................................................................73
3 of 74
, 1 - Fundamentals of algorithms
Algorithms – series of instructions used to solve a problem
4 of 74
AQA GCSE Computer Science (8525) - Aaryen Labana
Contents
1 - Fundamentals of algorithms...................................................................................................................4
Linear Search...........................................................................................................................................5
Binary Search...........................................................................................................................................5
Bubble Sort..............................................................................................................................................6
Merge Sort...............................................................................................................................................6
2 – Programming.........................................................................................................................................7
Data Types...............................................................................................................................................7
String Handling Operations......................................................................................................................7
Arithmetic Operations.............................................................................................................................8
Selection..................................................................................................................................................9
Iteration...................................................................................................................................................9
Nested Loop.............................................................................................................................................9
Infinite loops............................................................................................................................................9
Structure of indefinite and definite iteration.........................................................................................10
Records..................................................................................................................................................10
Dictionaries............................................................................................................................................10
Difference between Functions and Procedures.....................................................................................11
Subroutines............................................................................................................................................11
Flowcharts.............................................................................................................................................11
Pseudocode...........................................................................................................................................12
Trace Tables...........................................................................................................................................13
3 – Fundamentals of data representation.................................................................................................13
Units, binary and hexadecimal numbers................................................................................................13
Binary.................................................................................................................................................13
Hexadecimal Numbers.......................................................................................................................14
Binary Arithmetic...............................................................................................................................15
Overflow errors..................................................................................................................................16
Binary Shift.........................................................................................................................................16
Representing Text using binary..............................................................................................................17
1 of 74
, Ascii....................................................................................................................................................17
Character Encoding............................................................................................................................18
Unicode..............................................................................................................................................18
Representing images.............................................................................................................................19
Converting Binary data into a Bitmap and back.................................................................................20
Representing Sound..............................................................................................................................20
Compression..........................................................................................................................................22
Compression in images using RLE......................................................................................................23
Compressing text with Huffman trees...............................................................................................24
4 – Computer systems...............................................................................................................................27
Types of computer systems...................................................................................................................27
Boolean Logic.........................................................................................................................................29
Computer Memory................................................................................................................................30
Secondary Storage.................................................................................................................................32
Cloud storage.........................................................................................................................................37
CPU........................................................................................................................................................38
Software................................................................................................................................................42
Language Translators.............................................................................................................................45
5 – Fundamentals of computer networks..................................................................................................48
What Are Computer Networks?............................................................................................................48
Types of Network...................................................................................................................................48
Wired and Wireless Networks...............................................................................................................49
Network Cables......................................................................................................................................50
Wired Networks.....................................................................................................................................51
Wireless Networks.................................................................................................................................51
Wired Network Topologies....................................................................................................................53
Communicating across networks...........................................................................................................54
Network Protocols.................................................................................................................................56
Network Security...................................................................................................................................58
6 – Cyber security......................................................................................................................................62
Penetration Testing...............................................................................................................................62
Social Engineering..................................................................................................................................63
Protection Against Pharming.................................................................................................................64
2 of 74
, Protecting Against Social Engineering....................................................................................................64
Malware.................................................................................................................................................64
Protecting against Malware...................................................................................................................65
Detection and Prevention of Cyber Security Threats.............................................................................66
7 – Relational databases and Structured Query Language (SQL)...............................................................67
Relational Databases.............................................................................................................................67
Data Redundancy and Inconsistency.....................................................................................................70
Structured Query Language (SQL)..........................................................................................................71
8 – Ethical, legal and environmental impacts of technology on wider society, including issues of privacy
................................................................................................................................................................... 73
Data Protection Act:..............................................................................................................................73
Technologies..........................................................................................................................................73
3 of 74
, 1 - Fundamentals of algorithms
Algorithms – series of instructions used to solve a problem
4 of 74
