Computer Science key terms

A subprogram that returns a value to the code that called it.

A computer designed to run a wide range of programs for different purposes, such as word processing, browsing the web and playing games.

A unit of data equal to 1,000 megabytes using the decimal convention.

A unit of frequency equal to one billion cycles per second: $1\text{ GHz} = 10^9\text{ Hz}$.

A variable declared in global scope, outside subprograms, that can be accessed by subprograms as well as the main program.

An interface that allows users to interact through visual elements such as windows, icons, menus and a pointer.

A magnetic secondary storage device that offers high capacity and generally low cost per gigabyte, but contains moving parts.

The base-16 number system, using digits 0–9 and letters A–F. A–F represent denary values 10–15.

An arrangement in levels, from an overall problem to its main subsections and then more detailed tasks.

A programming language that uses human-readable commands and hides many details of the processor’s machine instructions.

Storing websites, files or other content on a server so that clients can access them over a network.

The maintenance and organisation tasks needed to keep a computer system in good working order.

Hypertext Transfer Protocol: rules for transferring web pages and other web content between browsers and web servers.

Hypertext Transfer Protocol Secure: a secure version of HTTP that encrypts data transferred between browsers and web servers.

The width and height of an image, measured in pixels.

Internet Message Access Protocol: rules for accessing and managing email while retaining messages on the server and synchronising changes across devices.

A range that includes its stated boundary values. For example, an inclusive range from 1 to 6 includes both 1 and 6.

Spacing at the beginning of lines of code that shows which statements belong within a block.

A number identifying a position in an array. In a zero-indexed array, the first position has index 0.

A loop that continues indefinitely because its stopping condition is never reached.

Data received by a program from outside it, for example from a keyboard or sensor.

Checking input against rules to decide whether it is acceptable for a program to process.

A sorting algorithm that builds a sorted section by taking each remaining item and inserting it into its correct position.

A command in a program that tells the CPU which operation to carry out.

A data type for whole numbers, including positive numbers, negative numbers and zero.

Division that returns the whole-number quotient rather than the fractional part; written as DIV in OCR pseudocode.

Software that brings together tools for writing, translating, running and debugging programs within one application.

Creations of the mind, such as software, writing, music and designs, that can be protected by law.

The output of one operation which becomes an input to a later operation in a combined Boolean expression.

A worldwide collection of interconnected computer networks.