Edexcel IGCSE Computer Science Glossary

constant

a 'container' that holds a value that never changes. Like variables, constant have unique identifiers.

hexadecimal

a base-16 number system. There are 16 digits and the place values increase in powers of 16.

code vulnerability

a computer program ( the code ) that has been written in such a way that it creates a security issue that may be taken advantage of to gain access to the computer system or data within it

debugger

a computer program that assists in the detection and correction of errors in other computer programs

agent

a computer system that can interpret its environment ( through its sensors ). It can act autonomously upon that environment ( through its effectors )

back-up

a copy of files in another location so that they are still available if the original copy is damaged or lost. Backing up is the process of making a back-up copy.

function

a function is a subprogram that performs a specific task and can be used at any point in the program. High-level programming languages have a number of useful built-in functions. You can also create your own or use functions available in online libraries

bus

a group of connections between devices in a computer

block of code

a grouping of two or more code statements

assembly language

a low-level language written using mnemonics

gigaertz (GHz)

a measure of frequency equivalent to 1000 million cycles per second

function machine

a metaphor or diagram that represents a machine that takes an input. It applies a rule such as a set of operations and delivers the answer as an output.

client-server network

a network that has at least one server to provide services to the client computers

developer

a person whose job is to create new software

algorithm

a precise method for solving a problem. All instructions given to a computer must be unambiguous or it won't know what to do.

dual-core processor

a processor with two processor cores

high-level programming language

a programming language that is similar to natural human language

Bluetooth

a protocol for the short-range wireless interconnection of mobile phones, computers, and other electronic devices

audit trail

a record of activities that have taken place on a computer system. This record is generated automatically and will record what has happened and who or what made the change.

ethics

a set of moral principles that govern a person's behaviour

construction

a smaller part from which something is built, Letters and numbers (i.e A to Z and 0 to 9 ) are the constructs we use to build our language and convey meaning. Bricks and cement are the basic constructs of a building

checksum

a technique for finding errors. A mathematical formula is applied to the date and the resulting number value is tansmitted with the date. The recipient computer applies the same formula to the received data. It then compares the checksum sent with the date to the calculated checksum. If the checksums don't match, the data is likely to have been corrupted. So, the recipient computer requests the data again.

cache

a temporary data store so that the data can be accessed very quickly when needed

compiler

a translator that converts high-level language source code into object code, often machine code. The source code is translated all at once and saved to be executed later.

heuristic

a type of algorithm capable of finding a solution to a problem quickly and easily. This is done through trial and error and educated guesswork to cut corners and remove less likely alternatives. Heuristic algorithms don't always find the best solution, but they will usually find one that works

identifier

a unique name given to a variable or a constant. Using descriptive names for variables makes code much easier to read

firewall

a utility that controls program access to the network, both incoming and outgoing

defragmenter

a utility that moves file clusters on a disk so they are closer to each other in order to speed up disk access

global variables

a variable that can be accessed from anywhere in the program, including inside subprograms

disk trashing

a very high rate of hard disk access

brute force

an algorithm design that does not include any techniques to improve performance, but instead relies on computing power to try all possibilities until the solution to a problem is found

divide and conquer

an algorithm design that works by dividing a problem into smaller and smaller sub-problems, until they are easy to solve. The solutions to these are then combined to give a solution to the complete problem

Denial of Service ( DoS )

an attack on a network that attempts to prevent legitimate users from accessing its services

clock

an electronic device inside a CPU that 'ticks' at regular intervals and is used to synchronise the actions of the other parts of the CPU

bug

an error or flaw in a computer program

field

an individual element in a record

binary shift

an operation done on all the bits of a binary value in which they are moved by a specific number of places to either left or right

arithmetic operator

an operator that performs calculation on two numbers

Creative Commons

an organisation that allows people to set copyright terms for their intellectual property. One use of a Creative Commons license is to allow people to copy material as long as it is not used commercially.

data structure

an organised collection of related elements, Arrays and records are two common data structures used in programming.

array

an organized collection of related values that share a single identifier

e-waste

any form of discarded electronic equipment, including computing technology

cyber attack

any kind of malicious attack on a network connected device

decomposition

breaking a problem down into smaller, more manageable parts, which are then easier to solve

compression

changing the format of a data file so that the size of the file becomes smaller

entanglement

co-dependence of the quantum states of pairs or groups of particles

application programming interface ( API )

code that allows two programs to communicate each other

DNA

deoxyribonucleic acid. It is a self-replicating material which is present in nearly all living organisms as the main constituent of chromosomes. It is carrier of genetic information.

ciphertext

encrypted plaintext

digital inclusion

ensuring that everyone has affordable access to computing technology and the necessary skills to take advantage of it

Hypertext Markup Language ( HTML )

essentially a text document that contains any text to be displayed along with: -details of how the text should be formatted (e.g. font, size, colour, etc. ) -details of any hyperlinks and where they link to using a URL -details of any objects such as pictures or videos that should be shown within the web-page when it is displayed

built-in functions

functions that are provided in most high-level programming languages to perform common tasks

central processing unit ( CPU )

hardware device that carries out the processing in a computer

emulator

hardware or software that allows one type of computer system to behave like another

eavesdrop

having unauthorised sight of data being sent from one computer to another over a network

digital

information represented by certain fixed values ( e.g. high, medium or low ). Any signal between these values would be meaningless and not used. Sending and receiving systems do not have to be as accurate as for analogue communication.

binary

information represented by only two values ( e.g. voltage or no voltage ; on or off ). There are no communication errors or misunderstandings because there are no small differences

cache memory

memory used to make up for the difference in speed between two internal components

decimal prefix

multiplies a unit by powers of 10

binary prefix

multiplies a unit by powers of 2

concurrent

processes that run at the same time are described as being concurrent

cloud storage

secondary storage, often belonging to a third party, that is accessed via a network, usually the internet, and so is not in the same physical place as the machine's RAM/ROM. Files stored "in the cloud" can be accessed from anywhere via an Internet connection

autonomous

self-directed and acts without requiring any help or guidance. Can choose its own goal and uses its experience to achieve it.

fetch-decode-execute cycle

sequence of steps carried out repeatedly by a CPU

flowchart

shows an algorithm as a diagram. Each step in the algorithm is represented by a symbol. Symbols are linked together with arrows showing the order in which steps are completed.

application software

software that performs a task that would otherwise be done by hand, perhaps a pen and paper

Boolean

something that can take only the values True or False ; named after English Mathematician George Boole

effectors

something that produces an effect by carrying out an action

IF...THEN...ELSE statement

the IF...THEN...ELSE statement allows a choice to be made between two alternatives based on whether or not a condition is met ( e.g. IF it is cold THEN wear a jumper ELSE wear a T-shirt )

assignment statement

the SET .. TO command is used to initialise variables in pseudocode

hacking

the act of gaining unauthorised access to a computer system and the data it contains

carbon footprint

the amount of carbon dioxide an individual or organization produces as a result of the energy they consume

bandwidth

the amount of data that can be carried on a network in a given period of time

byte

the basic combination of bits used to represent an item of information. A byte typically consists of 8 bits

character set

the defined list of characters recognised by a computer's hardware and software

digital divide

the gap between people who are technology-empowered and those who are technology-excluded

concatenation

the linking together of two or more items of information

communication media

the means by which data is transmitted between devices on a network. Coaxial cable, fibre-optic and microwaves are all forms of communication media.

colour depth

the number of bits used to encode the colour of each pixel

bit depth

the number of bits used to encode the information from each sample. Increasing the number of bits used increases the amount of detail contained in each sample.

bus width

the number of wires that make up a bus. This determines the range of binary numbers that can be communicated

control unit

the part of CPU that organises the actions of the other parts of the CPU

arithmetic/logic unit ( ALU )

the part of the CPU that performs calculations and logic operations

execution

the process by which a computer carries out the instructions of a computer program

authentication

the process of providing to a computer system who you are ( e.g. using a username and password )

abstraction

the process of removing or hiding unnecessary detail so that only the important points remain

encryption

the process of turning information ( e.g. a message ) into a form that only the intended recipient can decode , or decrypt and read. The message is encoded using an agreed method or algorithm. This is called the key. The encrypted is called a cipher.

fidelity

the relationship between the original sound and the recording. The greater the fidelity, the greater the similarity between them. Very high accuracy is called hi-fidelity or just hi-fi.

binary digit ( bits )

the smallest unit of data that is represented in a computer. It has a single binary value , either 1 or 0.

identity theft

the stealing of someone's personal details, such as their bank account number, sort code or passport number, for the purpose of making purchases and running up debts in their name

computational thinking

the thought processes involved in formulation problems and their solutions so that the solutions are represented in a form that can be effectively carried out by a computer

access control

this decides which users have access to which data, and what they are allowed to do with it

descending order

this is arranging items from largest to smallest ( e.g. 6,5,4,3,2,1, or f,e,d,c,b,a )

ascending order

this is arranging items from smallest to largest ( e.g. 1, 2 ,3 ,4, 5, 6, 7, or a, b, c, d )

domain name

this is part of the URL for a resource on the Internet. When the domain name is used, it will be converted to the correct IP address by the domain name service ( DNS ) and the contact will take place

definite iteration

this is used when the number of iterations, or 'turns of the loop', is known in advance. It can be set to as many turns as you want. This sort of loop is said to be "count controlled"

assembler

translates the mnemonics of assembly language programs into machine language instructions for the microprocessor to carry out

arithmetic shift

used for signed binary numbers. When performing a right shift, the bits at the left are replaced by copies of the most significant bit

analogue

using signals or information represented by a quantity ( e.g. an electric voltage or current ) that is continuously variable. Changes in the information being represented are indicated by changes in voltage. This method requires very accurate sending and receiving systems.

cache miss

when the data requested for processing by a component or application is not found in the cache memory