Cameroon GCE O-Level Computer Science key terms

The main processor chip that fetches instructions from memory, decodes them, and executes them. It contains the control unit, arithmetic logic unit and registers, and coordinates all other hardware components.

The part of the CPU that performs arithmetic operations such as addition and subtraction and logical comparisons such as AND, OR and greater-than. Results are passed back to registers or memory.

A very small, very fast storage location inside the CPU used to hold the current instruction, addresses and data during processing. Registers are far quicker than cache or RAM but hold tiny amounts of data.

The rate at which a processor executes its internal cycles, measured in hertz, megahertz or gigahertz. A higher clock speed usually means more instructions completed per second, though other factors also affect performance.

A small, high-speed memory between the CPU and main memory that stores recently or frequently used instructions and data. It reduces the time the processor waits for slower RAM.

Volatile main memory that holds the programs and data currently in use. Its contents are lost when power is switched off, and more RAM generally allows more programs to run at once.

Non-volatile memory whose contents are written during manufacture and normally cannot be changed by the user. It stores firmware such as the bootstrap program needed to start the computer.

Software stored permanently in hardware, typically in ROM or flash memory, that controls a device at a low level. Examples include the BIOS or UEFI that starts a computer and device controller programs.

Any hardware device connected to and controlled by the computer but not part of the CPU or main memory, such as a keyboard, printer or scanner. Peripherals may be input, output or storage devices.

Hardware that sends data or instructions into a computer for processing, for example a keyboard, mouse, scanner, microphone or barcode reader. The choice of device depends on the type and volume of data.

Hardware that presents processed results from a computer to the user, such as a monitor, printer, speaker or projector. Output may be soft copy on screen or hard copy on paper.

Non-volatile storage that keeps programs and files permanently when the computer is off, including hard disks, solid-state drives, optical discs and flash drives. It is slower than RAM but much larger and cheaper per byte.

A base-2 number system using only the digits 0 and 1, where each position represents a power of two. Computers use it because electronic circuits have two reliable states, off and on.

The smallest unit of data in a computer, a single binary digit that is either 0 or 1. Bits are grouped into bytes and used to represent numbers, characters, images and instructions.

A group of eight bits treated as one unit. One byte can represent 256 different values, enough for a character code or a small unsigned number.

A base-16 number system using digits 0 to 9 and letters A to F. It is used as shorthand for binary because one hexadecimal digit represents exactly four bits.

A method of representing negative integers in binary by inverting the bits of the positive value and adding one. The leftmost bit indicates the sign, and the range of values is asymmetric.

A defined list of characters each mapped to a unique numeric code, such as ASCII or Unicode. The code allows text to be stored and exchanged between different computer systems.

A basic electronic circuit that performs a Boolean operation on one or more binary inputs to produce a single output. Common gates are NOT, AND, OR, NAND, NOR and XOR.

A table listing every possible combination of inputs to a logic circuit and the resulting output for each. It is used to define, analyse and verify the behaviour of gates and circuits.

A statement built from variables and logical operators AND, OR and NOT that evaluates to true or false. It can be simplified with rules such as De Morgan's laws and drawn directly as a logic circuit.

System software that manages hardware, memory, files and processes and provides a platform on which application programs run. It also offers a user interface and enforces security and access rights.

A small system program that performs maintenance tasks such as virus scanning, disk defragmentation, backup, compression or file recovery. Utilities support the operating system rather than performing user work directly.

A translator that converts a whole program written in a high-level language into machine code before it is run, producing an executable file. Errors are reported after translation of the entire source.

A translator that converts and executes a high-level program one statement at a time, stopping when an error is found. It is useful for testing but usually runs more slowly than compiled code.

Program instructions written by a programmer in a high-level or assembly language before translation. It must be converted into machine code before the processor can execute it.

A finite, ordered set of unambiguous steps that solves a problem or completes a task. Every step must be precise and the process must terminate after a limited number of operations.

A structured, English-like way of writing an algorithm using keywords such as INPUT, IF, WHILE and ENDIF. It is not tied to any programming language and is easily converted into real code.

A diagram that represents an algorithm using standard symbols: ovals for start and end, parallelograms for input and output, rectangles for processes and diamonds for decisions, joined by arrows.

A named storage location in a program whose value can change while the program runs. It has a data type that determines what values it may hold and which operations are allowed.

A named value that is set once and cannot be changed while the program runs, such as the value of pi. Using constants improves readability and prevents accidental alteration.

A classification of data that defines the kind of values it can take and the operations allowed on it, for example integer, real, character, string or Boolean. It also determines storage space needed.

A named block of code that performs a specific task and can be called from elsewhere in a program, optionally receiving parameters and returning a value. It makes programs easier to reuse and maintain.

A value passed into a subprogram when it is called so that the subprogram can work on different data each time. Parameters are received into local variables inside the subprogram.

An organised collection of related data stored so that it can be easily accessed, managed and updated, usually through a database management system. Data is held in tables with controlled redundancy.

A field or combination of fields that uniquely identifies each record in a table. It must be unique for every record and cannot be left empty, ensuring no duplicate rows.

A field in one table that refers to the primary key of another table, creating a link between the two. It enforces referential integrity by preventing records that point to non-existent rows.

A rule ensuring that every value of a foreign key matches an existing primary key value in the related table. It prevents orphan records and keeps relationships between tables consistent.

Structured Query Language, used to create, query and modify relational databases. Common statements include SELECT to retrieve data, INSERT to add records, UPDATE to change them and DELETE to remove them.

The arrangement of devices and connections in a network, such as star, bus, ring or mesh. The choice affects cost, reliability and how easily faults can be located and repaired.

An agreed set of rules governing how data is formatted, transmitted and acknowledged between devices on a network. Examples include TCP/IP, HTTP, FTP and SMTP.

A unique numeric identifier given to a device on a network so data can be routed to it. IPv4 addresses are 32-bit and written as four decimal numbers separated by dots.

Hardware or software that monitors and filters incoming and outgoing network traffic against defined rules. It blocks unauthorised access while allowing legitimate communication to pass.

The process of converting readable data into an unreadable form using a key so that only authorised parties can decode it. It protects data during transmission and while stored.

A copy of data or programs kept separately so that the original can be restored if it is lost, damaged or corrupted. Backups should be regular, stored off-site and tested.

The staged process of building an information system, typically analysis, design, implementation, testing, deployment and maintenance. Each stage produces documentation and is reviewed before the next begins.

An early investigation that decides whether a proposed system is technically, economically and operationally practical. Its report recommends whether to proceed and may compare alternative solutions.

Testing carried out by developers and internal testers within the organisation before the software is released to users. It aims to find defects early using both valid and invalid test data.

Testing in which a nearly finished version of the software is given to real users outside the development team. Their feedback identifies problems that internal testing missed before the final release.

Material provided to help end users operate a system, including installation guides, tutorials, reference manuals and troubleshooting help. It is written in non-technical language and often includes screenshots.