Hexadecimal

Hexadecimal Numbers

Hexadecimal is faster for humans to process than binary. Hexadecimal allows us to find errors more easily. Hexadecimal is used in every computer system.

Hexadecimal

Hexadecimal or hex uses 16 different symbols for each place.
- This means hexadecimal is a base-16 numerical system.
Hexadecimal uses the digits 0-9, then A-F:
- A = 10 in denary, B = 11 , C = 12, D = 13 and so on.
Each digit's place value is multiplied by 16 as we move from right to left.

Advantages

An 8-bit binary number can be represented by two hexadecimal digits.
- This means you can reduce processing time with hexadecimal than with binary.
Hex is easier and faster to write two digits than the full binary sequence.
It is easier for a human to process hexadecimal than binary.

Using hexadecimal

Hexadecimal is used extensively in programming languages such as:
- Machine code.
- Assembly.
Hex can be used during the debugging stage of writing programs as it is easy to process by humans.
Hex can represent numbers stored in a CPU's registers or in main memory.

Using Hexadecimal

Hexadecimal is used in HTML to display colour on websites and to form unique MAC addresses for devices connected to a network.

HTML colours

In HTML, colours are defined by how much red, green and blue (RGB) there is on a scale of 0 to 255.
- 0 to 255 is the range of numbers that can be represented as a single byte.
- This means we use 2 hexadecimal digits to represent each RGB value.
HTML colour codes start with a hash symbol followed by 3 pairs of hexadecimal numbers like #00FF00.

HTML colours

We can break down the HTML colour code #00FF00 in the following way:
- The red value is 00, which means we have 0 units of red.
- The green value is FF, so we have 255 units of green.
- The blue value is 00, so we have 0 units of blue.
The colour code #00FF00 corresponds to a bright green colour.

MAC addresses

A MAC address is a number that uniquely identifies a networked device.
A MAC address is made up of 48 bits which are shown as 6 groups of 2 hexadecimal digits:
- NN-NN-NN-DD-DD-DD or NN:NN:NN:DD:DD:DD
The first 6 hex digits identify the device manufacturer.
The second 6 hex digits identify the serial number of the device.

1Computer Systems

1.1Systems Architecture

1.1.1Architecture Introduction

1.1.2Von Neumann Architecture

1.1.3Fetch-Execute Cycle

1.1.4Factors Affecting CPU Performance

1.1.5Elements of Computer Systems

1.1.6Exam-Style Questions - Von Neumann Architecture

1.2Memory & Storage

1.3Computer Networks, Connections & Protocols

1.4Network Security

1.4.1Forms of Attack

1.4.2Malware

1.4.3Social Engineering

1.4.4Phishing

1.4.5Common Active Attacks

1.4.6Information Security

1.4.7SQL Injection

1.4.8Network Administration

1.4.9Protecting Against Malware

1.4.10Authentication & Passwords

1.4.11Encryption

1.4.12End of Topic Test - Networks

1.5Systems Software

1.5.1Types of System Software

1.5.2Operating Systems

1.5.3Operating System Managers

1.5.4File Management

1.5.5Device Management

1.5.6User Management

1.5.7Utility Software: Encryption & Defragmentation

1.5.8Utility Software: Data Compression & Backup

1.6Ethical, Legal, Cultural & Environmental Concern

1.6.1Open Source vs Proprietary Software

1.6.2Licensing Issues

1.6.3Ethical Issues

1.6.4Ethical Issues 2

1.6.5Exam-Style Questions - Ethical Issues

1.6.6Legal Issues

1.6.7Legal Issues 2

1.6.8Freedom of Information Act (2000)

1.6.9Cultural Issues

1.6.10Environmental Issues

1.6.11Positive Environmental Impact

1.6.12Privacy Issues

1.6.13Stakeholders

1.6.14End of Topic Test - Software & Issues

2Computational Thinking, Algorithms and Programming

2.1Algorithms

2.1.1Computational Thinking

2.1.2Algorithmic Thinking

2.1.3Pseudocode & Flow Diagrams

2.1.4Interpreting & Correcting Algorithm

2.1.5Completing Algorithms

2.1.6Search Algorithms

2.1.7Binary Search

2.1.8Overview of Sort Algorithms

2.1.9Bubble Sort & Insertion Sort

2.1.10Merge Sort

2.1.11Exam-Style Questions - Sorting Algorithms

2.2Programming Fundamentals

2.2.1Fundamentals

2.2.2Program Flow 1

2.2.3Program Flow 2

2.2.4Arithmetic & Relational Operators

2.2.5Boolean Operators

2.2.6Data Types

2.2.7Arrays

2.2.8Strings

2.2.9File Handling

2.2.10Structuring Data

2.2.11End of Topic Test - Programming

2.2.12Exam-Style Questions - Translation

2.3Producing Robust Programs

2.3.1Defensive Design Considerations

2.3.2Defensive Design Considerations 2

2.3.3Maintainability

2.3.4Testing

2.3.5Test Plans

2.3.6Error Types

2.3.7End of Topic Test - Programming

2.3.8Exam-Style Questions - Testing

2.4Boolean Logic

2.4.1Computational Logic

2.4.2Boolean Logic

2.4.3Boolean Operators

2.4.4Grade 9 - Logic

2.5Programming Languages & IDEs

2.5.1High-Level vs Low-Level Languages

2.5.2Translation - Compliers & Interpreter

2.5.3Translation - Assemblers

2.5.4Integrated Development Environments

2.5.5Exam-Style Questions - Translation

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