AQA GCSE Computer Science

GCSE · AQAComputer Science31 notes in 8 folders, 136 KB

Notes for AQA GCSE Computer Science (8525), in folders for the specification's eight topics in its order: algorithms, programming, data representation, computer systems, networks, cyber security, relational databases and SQL, and the ethical, legal and environmental impacts of digital technology. Programming notes use AQA pseudo-code and Python, and each topic has one note per sub-topic or small group of them. Follows the specification for exams from June 2027 (version 1.3).

Adding them puts a copy in your notes, in a folder of its own with the folders below, for you to change and turn into flashcards or a question deck. Download gives you a zip of markdown files, which opens in any notes app.

What is inside

Algorithms
- Algorithms, decomposition and abstraction4 KB
- Pseudo-code, flowcharts and trace tables4 KB
- Searching algorithms4 KB
- Sorting algorithms4 KB
Programming
- Data types, variables and constants4 KB
- Selection and iteration5 KB
- Arithmetic, relational and Boolean operators4 KB
- Arrays and records4 KB
- Input, output, strings and random numbers5 KB
- Subroutines and structured programming5 KB
- Validation, authentication and testing5 KB
Data representation
- Number bases4 KB
- Binary arithmetic and units of information4 KB
- Character encoding3 KB
- Representing images4 KB
- Representing sound3 KB
- Data compression4 KB
Computer systems
- Hardware, software and operating systems4 KB
- Boolean logic4 KB
- Programming languages and translators5 KB
- The CPU and the fetch-execute cycle4 KB
- Memory, storage and embedded systems6 KB
Computer networks
- Network types and connections4 KB
- Protocols and the TCP/IP model4 KB
- Network security4 KB
Cyber security
- Cyber security threats6 KB
- Detecting and preventing cyber security threats4 KB
Relational databases and SQL
- Relational databases3 KB
- SQL4 KB
Ethical, legal and environmental impacts
- Privacy, law and the ethics of digital technology6 KB
- Technologies and their impacts7 KB

The first note

Algorithms / Algorithms, decomposition and abstraction

## What an algorithm is An **algorithm** is an ordered list of steps for getting a task done, each one precise enough to follow exactly as written. A recipe, a set of directions to a shop and the method for long multiplication are all algorithms, and none of them needs a computer. What makes something an algorithm is that each step is precise enough to be followed without any further judgement, that the steps come in a definite order, and that the sequence finishes. A computer program is an implementation of an algorithm: the same algorithm can be written as a Python program, a C# program or a VB.NET program, and each of those is a different program for one algorithm. It follows that an algorithm is not a program. The algorithm is the idea, and the program is that idea written in a language a computer can run. ## Inputs, processing and outputs Nearly every algorithm can be described in three parts. The **inputs** are the data the algorithm is given, the **processing** is what it does with that data, and the **outputs** are the results it produces. In this algorithm for the mean of two numbers, the two lines that take data in are the inputs, the middle line is the processing and the last line is the output. ```text a ← USERINPUT b ← USERINPUT mean ← (a + b) / 2 OUTPUT mean ``` Being able to point at these three parts in an unfamiliar algorithm is the first step in working out what it does. Values that are read in, and anything taken from a file or a sensor, are inputs…

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