9618 CIE Computer Science

Binary

base two number system based on the values 0 and 1 only

Bit

abbreviation for binary digit.

Abstract class

a base class that is never used to create objects directly

Abstract Data Type

a collection of data with associated operations

Acceptance testing

testing of software by customers before sign-off

Accumulator

a general-purpose register that stores a value before and after the execution of an instruction by the ALU

Actuator

a hardware device that receives a signal from a computer and adjusts the setting of a controlling device

Adaptive maintenance

amending a program to enhance functionality or in response to specification changes

Address bus

a component that carries an address. This can be to the memory controller to identify a location in memory which is to be read from or written to or it can be to the 1/0 system to identify the source or destination of the data

Addressing mode

when the instruction uses a value this defines how the operand must be used to find the value

Algorithm

a sequence of defined steps that can be carried out to perform a task

Alpha testing

testing of software in-house by dedicated testers

Analogue data

data obtained by measurement of a physical property which can have any value from a continuous range of values

Argument

the actual input expression or value with which the subroutine is being called

Arithmetic shift

uses the shift to carry out multiplication or division of a signed integer stored in the accumulator

Array index

row or column number of an individual array element

Assembler

a program used to translate an assembly language program into machine code

Assembly language

a low-level language related to machine code where opcodes are written as mnemonics and there is a character representation for an operand

Asymmetric key encryption

there is a public key and a private key one of which is used for encryption and the other for decryption

Attribute

a column in a relation that contains values

Attributes

the data items of a class (also sometimes referred to as fields)

Authentication

verification of a user's identity

Authorisation

definition of a user's access rights to system components

Back propagation of errors

An algorithm for machine learning that optimises the values for parameters which are adjustable. It is applied first to the nodes in the output layer and then works backward t hrough the nodes in hidden layers until finally the input nodes are considered.

Bandwidth

a measure of the amount of data that ca n be transmitted per second

Base case

an explicit solution to a recursive function

Beta testing

testing of software by a limited number of chosen users before general release

Binary coded decimal (BCD)

storage of a binary value representing one denary digit in a nibble

Binary file

a file designed for storing data to be used by a computer program

Binary prefix

examples are kibi, mebi, gibi and tebi representing factors of 210, 220, 230 and 240 respectively to define the magnitude of a va lue

Binary search

repeated checking of the middle item in an ordered search list and discarding the half of the list which does not contain the search item

Bit depth

the number of bits used to represent each of the red, green and blue colours

Bit rate

the number of bits transmitted per second

Bit

a digit in the binary number system written using either of the symbols 0 and 1

Black-box testing

comparing expected results with actual results when a program is run

Bridge

a device that connects two segments of a LAN

Bubble sort

a sort method where adjacent pairs of values are compared and swapped

Buffer

a temporary storage created for data transmitted from one part of the system to another which functions as a queue

Bus topology

contains one shared link to which all devices are attached

By reference

the address of the variable is passed into the procedure

By value

the actual value is passed into the procedure

Byte

a group of eight bits treated as a single unit

Cable

a transmission using copper wire or fibre-optic

Candidate key

a key that could be chosen as the primary key

Capacitive touch screen

a rigid surface above a conductive layer that undergoes a change in electrical state when a finger touches the screen

Ciphertext

the result of applying an encryption algorithm to data

Class

a type that combines a data structure with the methods that operate on the data structure

Client-server

an architecture where a client runs an application provided by a server on a network

Combinational circuit

a circuit in which the output is dependent only on the input values

Complex Instruction Set Computer (CISC)

a single instruction can be more complex and involve more loading of data from memory

Constructor

a special type of method that is called to create a new object and initialise its attributes

Containment

a relationship in which one class has a component that is of another class type

Copyright

a formal recognition of ownership of a created and published work

Corrective maintenance

correcting identified errors

Cyclic shift

similar to a logical shift but bits shifted from one end reappear at the other end

Data bus

a component that can carry data from the processor to the memory or to an output device or can carry data from the memory or from an input device

Data integrity

a requirement for data to be accurate and up to date

Data management system (DBMS)

software that controls access to data in a database

Data privacy

a requirement for data to be available only to authorised users

Data protection law

a law that relates to data privacy

Data redundancy

the same data stored more than once

Data security

data that were stored must be available unchanged when needed which requires that only authorised users have had access and that data can be recovered if lost or corrupted

Database administrator (DBA)

a person who uses the DBMS to customise the database to suit user and programmer requirements

Debugging

finding and correcting errors, oft en called 'bugs', in a program

Decimal prefix

examples are kilo, mega, giga and tera representing factors of 103, 106, 109 and 1012 respectively to define the magnitude of a value.

Deep learning

where a system uses an artificial neural network with an exceptionally large number of hidden layers

Denary numbers

which are also known as decimal numbers are written using one of the symbols 0,1,2,3,4,5,6,7,8,9 for each denary digit

Developer interface

gives access to software tools provided by a DBMS for creating t ables

Digital data

data that has been stored as a binary value which can have one of a discrete range of values

Directive

an instruction to the assembler program

Disk thrashing

when paging is being used and a repetitive state has been reached where loading one page causes a need for another page to be loaded almost immediately but the loading of this new page causes the same immediate need

Domain name system (DNS)

a hierarchical distributed database installed on domain name servers that is responsible for mapping a domain name to an IP address

Drawing list

contains one set of values for each drawing object

Drawing object

a component defined by geometric formulae and associated properties

Dry-run (walk through)

the process of checking the execution of an algorithm or program by

Encapsulation

combining data and subroutines into a class and restricting external access to the data

End-system

a computer or server connected to a network

Enumerated data type

a non-composite user-defined data type for which the definition identifies all possible values

File header

a set of bytes at the beginning of a bitmap file which identifies the file and contains information about the coding used

Finite state machine {FSM}

a machine that consists of a fixed set of possible states with a set of inputs that change the state and a set of possible outputs

Firewall

hardware or software that monitors and controls network traffic

Floating-point representation

a representation of real numbers that stores a value for the mantissa and a value for the exponent

Flowchart

shapes linked together to represent the sequential steps of an algorithm

Foreign key

an attribute in one table that refers to the primary key in another table

Freeware

software provided free of charge with no time limit for its use but no source code provided

Free software

software provided with the source code when the user is free to use it as they wish

Full adder

circuit a circuit which performs binary addition of two individual bits and an input carry bit

Function / Procedure header

the first line of a function or procedure definition showing the identifier and parameter list

Function

a sequence of steps that is given an identifier and returns a single value; function call is part of an expression

General case

a definition of a recursive function in terms of itself

Getter

a method to access its associated attribute

Global variable

a variable that is accessible from all modules

Half adder circuit

a circuit which performs binary addition of two individual bits

High-level scheduler

makes decisions about which program stored on disk should be moved into memory

Hybrid network

a collection of connected LANs where some of them have different topologies or supporting technologies

Identifier table

a table listing the variable identifiers required for the solution, with explanations and data types (see Chapter 13)

Image resolution

the number of pixels in the bitmap file defined as the product of the width and the height values

Index

a small secondary table used for rapid searching which contains one attribute from the table being searched and pointers to the tuples in that table

Inheritance

all attributes and methods of the base class are copied to the subclass

Integration testing

individually tested modules are joined into one program and tested to ensure the modules interact correctly