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Computer Science and Computational Thinking Fundamentals
Exam Questions and Answers well Reviewed by Brian 13
th
edition 2025 - 2026
Computer science The study of computers, algorithmic processes, programming, computational thinking, computer systems, data, and the impact of computing on society. Computational thinking A problem-solving approach that uses ideas such as decomposition, abstraction, pattern recognition, logic and algorithms so that a solution can be automated or implemented by a computer. Decomposition Breaking a large or difficult problem into smaller, more manageable parts. Abstraction Ignoring unnecessary detail and focusing on the important features of a problem or system. Pattern recognition Identifying similarities, repeated structures or trends that can help solve a problem. Generalisation Creating a solution that works for a whole class of similar problems, not only one specific example. Algorithmic thinking Designing a clear sequence of steps that can solve a problem. Logic Reasoning about conditions that are either true or false, often using Boolean expressions and logic gates.
Automation Using computing technology to carry out tasks with little or no human intervention. Computational artefact A digital product created using computing, such as a program, website, simulation, animation, app, data visualisation or embedded system. Heuristic A rule-of-thumb or approximate problem-solving method used when finding the perfect solution would take too long or use too many resources. Model A simplified representation of a real-world system used to understand, predict or test ideas. Simulation A computer-based imitation of a real process or system, often used to test what might happen under different conditions. State The current condition or configuration of a system at a particular moment. State transition A change from one state to another caused by an input, rule or event. Finite State Machine (FSM) A model made of a finite number of states and rules for moving between states based on inputs. Turing machine A theoretical model of computation using states, rules and a tape. It is used to reason about what can and cannot be computed. Computable
Syntax error An error caused by breaking the grammar/rules of the programming language, so the code cannot run correctly. Logic error An error where code runs but gives the wrong result because the algorithm or reasoning is incorrect. Runtime error An error that occurs while a program is running, often because of invalid data or an impossible operation. Bug A mistake or fault in a program that causes incorrect or unexpected behaviour. Debugging Finding, understanding and fixing errors in a program. Comment Text in code for humans to read that is ignored by the computer when the program runs. Variable A named location/reference used to store a value while a program runs. Value The item of data stored in a variable, such as 5, 'hello' or True. Assignment Giving a value to a variable. In Python this is done using =, for example x = 5. Assignment operator The = symbol in programming when it assigns the right-hand value/expression to the variable on the left. Expression
A piece of code that evaluates to a value, such as x + 2 or len(names). Operator A symbol or keyword that performs an operation on values, such as +, - , , /, %, // or *. Operand A value or variable that an operator acts on. In x + 3, x and 3 are operands. Operator precedence The order in which operations are evaluated when there are multiple operators in an expression. Integer A whole number data type, such as - 3, 0, 5 or 255. In Python the type is int. Float A decimal/floating-point number data type, such as 3.14 or - 99.99. In Python the type is float. String A sequence of characters used for text, usually written inside quotes, such as 'Hello'. In Python the type is str. Boolean A data type with only two possible values: True or False. Data type A category of data that tells the computer what kind of value is being stored and what operations make sense. Type conversion / casting Changing a value from one data type to another, such as int('5') or str(25). Input
A Boolean expression used to decide whether a block of code should run. If statement A selection statement that runs a block of code only when a condition is True. Elif Python keyword meaning 'else if'; used to check another condition after a previous if/elif is False. Else A selection branch that runs when all previous if/elif conditions are False. Iteration / loop Repeating a set of instructions multiple times. For loop A loop that iterates over a sequence or a range of values, often when the number of iterations is known. While loop A loop that repeats while a condition remains True, often when the number of iterations is not known in advance. Nested loop A loop placed inside another loop. Infinite loop A loop that never ends because its stopping condition is never reached. List / array An ordered collection of values stored under one variable name. Python lists use square brackets. Element A single item in a list or array. Index
The position number used to access an item in a list or string. Python starts indexing at 0. Zero-based indexing A numbering system where the first item is at index 0, the second at index 1, and so on. Slice A part of a string or list selected using start and stop indexes, such as name[0:2]. len() A Python function that returns the number of items in a sequence such as a list or string. append() A list method that adds an item to the end of a list. Dictionary A Python data structure that stores key-value pairs. Tuple An ordered collection similar to a list but typically immutable. Module / library Reusable code that can be imported into a program to provide extra functions or tools. Import statement A statement that makes code from a module/library available in your program. Random value A value generated unpredictably within a defined range or set, often used in simulations/games. String concatenation Joining strings together using + or another method.
An input with discrete states, usually on/off, 1/0, True/False. Analogue input An input that can vary continuously over a range, such as light level or temperature. Digital output An output signal with discrete states, often HIGH/LOW or on/off. Analogue-to-digital conversion (ADC) The process of converting a continuous analogue signal into digital values a computer can process. Pin A connection point on a microcontroller used to send or receive electrical signals. Circuit A complete path through which electric current can flow. Voltage Electrical potential difference; a 'push' that can cause current to flow in a circuit. Current The flow of electric charge in a circuit, measured in amperes (A). Resistance Opposition to the flow of current, measured in ohms. Resistor A component that limits current flow in a circuit. Capacitor A component that stores electrical energy/charge and can release it. Transistor
A semiconductor component used as an electronic switch or amplifier; a basic building block of logic circuits and processors. Integrated circuit A chip containing many electronic components/transistors on a single piece of semiconductor material. Logic gate An electronic/computational component that performs a Boolean operation on one or more inputs to produce an output. Truth table A table listing every possible input combination and the corresponding output of a Boolean expression or logic circuit. AND gate Outputs 1/True only when all inputs are 1/True. OR gate Outputs 1/True when at least one input is 1/True. NOT gate Outputs the opposite of its input. XOR gate Outputs 1/True when inputs are different. Half adder A logic circuit that adds two binary bits and produces a sum and carry output. Full adder A logic circuit that adds two binary bits plus a carry-in, producing a sum and carry- out. Pulse-width modulation (PWM)
Data that is publicly available for people to use, reuse and share, often from governments or organisations. Data analytics The process of collecting, cleaning, analysing and interpreting data to find patterns, answer questions or support decisions. Hypothesis A testable prediction or proposed explanation that can be investigated using data. Data cleaning Finding and fixing/removing problems in data, such as missing values, duplicates, inconsistent formats or outliers. Validation Checking that input data is reasonable and follows rules before it is accepted or processed. Verification Checking that data has been entered or copied accurately from its source. Missing value A data item that is blank or absent when a value is expected. Duplicate record A repeated record that appears more than once in a dataset. Outlier / anomaly A value that is unusual compared with the rest of the data and may be an error or a genuine exceptional case. Inconsistent format When similar data is written in different formats, such as dates or times recorded differently. Mean
The arithmetic average: total of values divided by the number of values. Median The middle value when values are sorted. If there are two middle values, the median is their mean. Mode The most frequently occurring value in a dataset. Range The difference between the highest and lowest values. Frequency The number of times a value or category occurs. Data visualisation Representing data graphically, such as using bar charts, line graphs, pie charts or scatter plots. Bar chart A chart using separate bars to compare categories or discrete values. Line graph A chart using points connected by lines to show change over time or sequence. Pie chart A circular chart divided into sectors showing parts of a whole. Scatter plot A chart showing points for pairs of values, useful for spotting relationships/correlation. Axis label Text that identifies what a chart axis represents and often its unit. Legend
A model where a client requests a service/resource and a server processes the request and sends back a response. Request A message sent by a client asking a server for a resource or service. Response The server's reply to a client request, such as an HTML page or data. URL Uniform Resource Locator: the address used to locate a resource on the web. Protocol An agreed set of rules for communication between devices/systems. HTTP HyperText Transfer Protocol: protocol used for transferring web pages/resources between browser and server. HTTPS Secure version of HTTP that uses encryption/TLS to protect data in transit. TCP Transmission Control Protocol: breaks data into packets, numbers them, checks delivery and reassembles them in order. IP Internet Protocol: responsible for addressing and routing packets across networks. VoIP Voice over Internet Protocol: using IP networks to carry voice/video communication, such as Zoom or WhatsApp calls. Packet A small chunk of data sent across a network with addressing/control information.
Packet switching Sending data as separate packets that may travel different routes and are reassembled at the destination. IP address A numerical address used to identify a device/network interface on an IP network. DNS Domain Name System: translates human-readable domain names into IP addresses. Encryption Transforming data into unreadable form using a key so it cannot be understood without decryption. Decryption Converting encrypted data back into readable form using the correct key. HTML tag A markup instruction written in angle brackets, such as
or
.
HTML element A complete part of a webpage, usually made of an opening tag, content and a closing tag.
HTML attribute Extra information inside an opening tag, such as href in an tag.
Hyperlink A clickable link that takes the user to another page, file, section or resource.
Form A webpage section used to collect user input.
Event An action such as a click, keypress or form submission that code can respond to.
How the OS decides which process uses the CPU and when. Firmware Software stored in hardware, often in ROM/flash, that controls low-level device operation. CPU Central Processing Unit: the main processor that fetches, decodes and executes instructions. ALU Arithmetic Logic Unit: CPU component that performs arithmetic and logical operations. Control Unit (CU) CPU component that directs and coordinates operations, including fetching, decoding and executing instructions. Register A very small, very fast storage location inside the CPU used to hold data, instructions or addresses temporarily. Program Counter (PC) A register that stores the memory address of the next instruction to be executed. Accumulator (ACC) A CPU register used to store intermediate results/data being operated on by the ALU. Cache Fast, small memory close to or inside the CPU used to store frequently needed data/instructions. Clock speed The number of CPU clock pulses per second, usually measured in hertz; higher speed can mean more cycles per second.
Core A processing unit within a CPU capable of executing instructions. Fetch-decode-execute cycle The repeated process by which the CPU fetches an instruction from memory, decodes it, and executes it. RAM Random Access Memory: volatile primary memory used to store programs/data while the computer is running. ROM Read-Only Memory: non-volatile memory used to store permanent/start-up instructions such as firmware. Volatile memory Memory whose contents are lost when power is switched off, such as RAM and registers. Non-volatile memory Memory/storage that keeps data when power is off, such as ROM, SSDs and hard drives. Primary memory Memory directly accessible by the CPU, mainly RAM, ROM and cache/registers. Secondary storage Long-term non-volatile storage for files and programs, such as HDDs, SSDs and USB drives. HDD Hard Disk Drive: magnetic secondary storage with spinning platters and moving parts. SSD
