Computing Glossary

By Tamsin Newlove

ALU (Arithmetic and Logic Unit)

The ALU carries out calculations such as addition, subtraction, multiplication and division. It also compares numbers. For example, whether number A is greater than number B.

Assembly Language

A slightly more people-friendly language that is also called ‘Machine Code’. It is a stage between higher code and binary.


A coding language that computers use. It has only two values 1 (true) and 0 (false).


One value in a binary code. (It is either a one or a zero.)


A data type that refers to an expression or variable that is either true or false.


The measurement of storage space on a computer. A byte is equal to 8 bits.

Cache Memory

Cache is type of memory used in a CPU. It speeds up the way applications work.

Clock Speed

Speed is the speed at which the CPU carries out an instruction. It is measured in Gigahertz. 1 Hertz is 1 instruction per second. 1 Gigahertz is 1 billion instructions per second.

Command Line

An interface that requires you to interact with the computer using a series of text commands.

CPU (Central Processing Unit)

The CPU is the ‘brain’ of the computer. It is a microchip that fetches, decodes and executes instructions and performs calculations.

Dual Core

Dual Core Processor is more than one CPU core on the same trip within the same computer. This allows more instructions to be completed and increases the speed of the CPU.

Fetch-Execute Cycle

Firstly, the CPU fetches some data from the main memory. Then, the CPU decodes the instructions and determines which areas within the microchip will need to be used. Finally, the instructions are executed before the cycle begins again.

Graphical User Interface

A Graphical User Interface is a common interface where the user clicks on icons to carry out actions. For example, Windows or Apple.


An integer is a variable type that will only store whole numbers.


The Motherboard is the main printed circuit board in the computer. This is where the CPU, memory and peripheral devices are connected.


A description of the file or image and it's size (in pixels), colour depth, the date and the time that the image was created.

Operating System

A piece of software that manages the other components in the computer.


M - Mulititasking

U - User Interface

M - Memory Management

P - Peripheral Management

S - Security


When a computer adds two binary numbers, sometimes the result is larger than the space that it is allocated to. This causes the program to shut down or leaves inaccurate data.


Pixel is short for Picture Element. A Pixel is the smallest dot that can be created on a computer screen. The more pixels per inch the better the quality of the image.


Pseudocode is a detailed description of a program that explains what the code is doing and how it is structured.

RAM (Random Access Memory)

When a program is being used, the information, data and instructions for that program are stored in the RAM. It is smaller and faster than a Hard Disk. The content of the RAM is volatile which means that it is lost when the computer looses power.

ROM (Read Only Memory)

ROM stores information that doesn't need altering as it cannot be edited or deleted. It is non-volatile so it is not affected by whether the computer is on or not. It usually stores bootstrapping instructions which tell the computer how to find and initialise the operating system when the computer is turned on.


Unicode is binary code that is used to represent characters. It requires 16 bits of storage but can store 65,563 characters.

Virtual Memory

The Operating System sets aside part of the Secondary Storage to use as Temporary Memory. If the RAM is running out of room, the least used data is transferred to that part of the Secondary Storage. This is virtual memory.