Fetch-Execute Cycle

The Fetch, Decode, Execute Cycle

To process instructions and data, the processor needs to retrieve them from memory. To do this, it follows the fetch, decode, execute (FDE) cycle.

Fetch

The address of the instruction that needs to be processed next is copied from the Program Counter (PC) to the Memory Address Register (MAR).
The PC is incremented to point to the next instruction that will be needed when the cycle starts again.
The instruction stored at the location held by the MAR is copied to the MDR.

Decode

The Control Unit decodes the instruction and sends control signals to the component within or outside the CPU that needs to act.

Execute

The operation indicated by the instruction is performed by the appropriate component. For example:
- The Arithmetic Logic Unit (ALU) performs the operation given by the Control Unit.
- The value stored by the Program Counter or Memory Address Register might be changed.

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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