AQA GCSE Computer Science revision checklist

3.1.1 Representing algorithms

• I can explain what an algorithm is, and that a program is one way of implementing an algorithm.
• I can explain decomposition: breaking a problem into smaller sub-problems.
• I can explain abstraction: removing unnecessary detail from a problem.
• I can write algorithms in pseudo-code (including AQA's own style), in program code and as flowcharts.
• I can point out the inputs, processing and outputs in an algorithm.
• I can work out what a simple algorithm does, using a trace table or by reading it carefully.

3.1.2 Efficiency of algorithms

• I can explain that different algorithms can solve the same problem.
• I can compare how time-efficient two algorithms are for the same problem.

Revise it: Searching algorithms · Sorting algorithms

3.1.3 Searching algorithms

• I can explain how a linear search works, step by step.
• I can explain how a binary search works, step by step, and that the list must be sorted first.
• I can compare linear and binary search, with an advantage and a disadvantage of each.

Revise it: Searching algorithms

3.1.4 Sorting algorithms

• I can explain how a bubble sort works, pass by pass.
• I can explain how a merge sort works: splitting, then merging back in order.
• I can compare bubble sort and merge sort, with an advantage and a disadvantage of each.

Revise it: Sorting algorithms

3.2.1 Data types

• I can explain what a data type is.
• I can choose and use the right data type: integer, real, Boolean, character or string.

3.2.2 Programming concepts

• I can use variables, constants and assignment, and explain why named constants and variables are used.
• I can combine sequence, selection and iteration in a program.
• I can use count-controlled (definite) loops, like FOR.
• I can use condition-controlled (indefinite) loops, with the condition at the start or at the end.
• I can use nested selection and nested loops.
• I can choose meaningful names for variables, constants and subroutines, and explain why it matters.

3.2.3 Arithmetic operations

• I can use addition, subtraction, multiplication and real division.
• I can use integer division and remainders (DIV and MOD) — for example, 11 DIV 2 is 5 and 11 MOD 2 is 1.

3.2.4 Relational operations

• I can use and interpret equal to, not equal to, less than, greater than, and less/greater than or equal to.

3.2.5 Boolean operations

• I can use NOT, AND and OR, and combine them, in the conditions of loops and IF statements.

3.2.6 Data structures

• I can explain what a data structure is.
• I can use one-dimensional and two-dimensional arrays (or lists) to solve simple problems.
• I can use records to group related data about one thing.

3.2.7 Input and output

• I can get input from the keyboard and display output on the screen.

3.2.8 String handling

• I can find a string's length and the position of a character in it.
• I can take a substring and join strings together (concatenation).
• I can convert between characters and character codes.
• I can convert between strings and integers or real numbers.

3.2.9 Random number generation

• I can use random numbers in my programs.

3.2.10 Subroutines and structured programming

• I can explain what a subroutine is, and the advantages of using them.
• I can pass data into a subroutine using parameters, including more than one.
• I can write subroutines that return a value.
• I can explain local variables — they only exist while the subroutine runs, and only inside it — and why using them is good practice.
• I can describe the structured approach to programming and its advantages.

3.2.11 Robust and secure programming

• I can write simple validation routines, like length, presence and range checks.
• I can write a simple username and password check.
• I can explain what testing is, and find and fix errors in algorithms and programs.
• I can describe normal, boundary and erroneous test data, and choose suitable test data for a problem.
• I can tell the difference between a syntax error and a logic error.

3.3.1 Number bases

• I can explain decimal (base 10), binary (base 2) and hexadecimal (base 16).
• I can explain that computers use binary for all data and instructions.
• I can explain why hexadecimal is often used in computer science.

Revise it: Binary and denary · Hexadecimal · Two's complement

3.3.2 Converting between number bases

• I can convert between binary and decimal, for values from 0 to 255.
• I can convert between binary and hexadecimal, and between decimal and hexadecimal (up to FF).

Revise it: Binary and denary · Hexadecimal

3.3.3 Units of information

• I can explain that a bit is a 0 or a 1, and a byte is 8 bits.
• I can use kilobytes, megabytes, gigabytes and terabytes (each 1,000 of the one before) and compare amounts of data.

3.3.4 Binary arithmetic

• I can add up to three binary numbers, carrying correctly, and spot when the answer overflows into a 9th bit.
• I can apply a logical binary shift, left or right.
• I can describe where binary shifts are useful: multiplying and dividing by powers of 2.

Revise it: Binary shifts · Binary addition

3.3.5 Character encoding

• I can explain what a character set is, and describe 7-bit ASCII and Unicode.
• I can use a character table to convert characters to codes and back, using the fact that codes run in sequence.
• I can explain why Unicode is needed and its advantages over ASCII.

3.3.6 Representing images

• I can explain what a pixel is and how pixels make up a bitmap image.
• I can explain image size (width × height in pixels) and colour depth.
• I can explain how more pixels or a higher colour depth affect file size.
• I can calculate a bitmap's file size: width × height × colour depth.
• I can turn binary into a simple bitmap, and a simple bitmap into binary.

Revise it: Representing images

3.3.7 Representing sound

• I can explain why analogue sound must be sampled to store it digitally.
• I can explain sampling rate and sample resolution.
• I can calculate a sound file's size: sampling rate × sample resolution × seconds.

Revise it: Representing sound

3.3.8 Data compression

• I can explain what compression is and why data is compressed.
• I can explain Huffman coding and read a Huffman tree.
• I can work out how many bits Huffman coding saves compared with ASCII.
• I can explain run length encoding (RLE) and write data as frequency/data pairs.

3.4.1 Hardware and software

• I can define hardware and software and explain how they depend on each other.

3.4.2 Boolean logic

• I can draw truth tables for NOT, AND, OR and XOR gates.
• I can complete truth tables for circuits with up to three inputs.
• I can draw, change and read simple logic circuit diagrams.
• I can write Boolean expressions using . (AND), + (OR), ⊕ (XOR) and an overbar (NOT).
• I can turn a circuit into a Boolean expression, and an expression into a circuit.

Revise it: Logic gates

3.4.3 Software classification

• I can explain system software and application software, with examples of each.
• I can explain what an operating system manages: the processor, memory, input/output devices, applications and security.
• I can explain what utility programs are for.

3.4.4 Programming languages and translators

• I can explain the differences between low-level and high-level languages, and why most programs are high-level.
• I can explain the difference between machine code and assembly language.
• I can give the advantages and disadvantages of low-level programming.
• I can explain what interpreters, compilers and assemblers do, and when each is used.

3.4.5 Systems architecture

• I can explain the roles of main memory, the ALU, control unit, clock, registers and buses.
• I can explain how clock speed, number of cores and cache size affect CPU performance.
• I can explain the fetch-execute cycle.
• I can explain what RAM, ROM, cache and registers are each used for.
• I can explain the difference between main memory and secondary storage, and between volatile and non-volatile.
• I can explain why secondary storage is needed, and compare solid state and magnetic storage.
• I can explain cloud storage, and its advantages and disadvantages compared with local storage.
• I can explain what an embedded system is, with examples of embedded and non-embedded systems.

Revise it: Systems architecture

• I can explain what a network is, with its advantages and disadvantages.
• I can describe PAN (Bluetooth), LAN and WAN networks.
• I can compare wired and wireless networks, including fibre and copper cable.
• I can explain what a protocol is, and the purpose of TCP, IP, HTTP, HTTPS, SMTP and IMAP.
• I can explain why network security matters, and how authentication, encryption, firewalls and MAC address filtering protect a network.
• I can describe the four layers of the TCP/IP model and which protocols work at each.

3.6.1 Fundamentals of cyber security

• I can define cyber security and describe what it's for.

3.6.2 Cyber security threats

• I can explain threats including pharming, weak and default passwords, misconfigured access rights, removable media, and unpatched or outdated software.
• I can explain what penetration testing is and what it's used for.

3.6.2.1 Social engineering

• I can explain social engineering — blagging, phishing and shouldering — and how to protect against it.

3.6.2.2 Malware

• I can explain malware — viruses, trojans and spyware — and how to protect against it.

3.6.3 Detecting and preventing threats

• I can explain biometrics, password systems, CAPTCHA, email confirmations and automatic software updates as security measures.

3.7.1 Relational databases

• I can explain what a database and a relational database are.
• I can explain tables, records, fields, data types, primary keys and foreign keys.
• I can explain how relational databases cut out data redundancy and inconsistency.

3.7.2 SQL

• I can retrieve data with SELECT, FROM, WHERE and ORDER BY (ASC or DESC), from one or two tables.
• I can add, change and delete data with INSERT INTO, UPDATE and DELETE.

• I can explain the ethical, legal and environmental impacts and risks of digital technology, including privacy, using examples from cyber security, mobile and wearable technology, wireless networking, cloud storage, hacking, computer-based implants and autonomous vehicles.