AQA COMP1 Extracted Definition

7/27/2019 AQA COMP1 Extracted Definition

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BitmapCreated when the pixels of an image are mapped to positions inmemory that store binary codes representing the colour of eachpixel.

Black-boxtesting(functional testing)

It is carried out without looking at the program code.

Boolean data Can be one of two possible values, True or False.

Booleanexpression

Returns True or False.

Boolean

operatorsNOT, AND, OR.

Boundaries(Deningboundaries)

Establishing the limits or rules about what can and cannot bedone when solving a problems. These limits are a type of constraint.

Boundaries(Lateralthinking)

Used to challenge assumptions, establish facts and rules anddene the boundaries of problem solving.

Byte A group of 8 bits.


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Character Any letter, numeral or symbol in the given character set, such asthe ASCII character set.

Colour depthThe number of bits used to represent the colour of a single pixelin a bitmapped image.

Compilationerror

When a program does not compile because of syntax errors or lexical errors.

Compiler A program that translates source code into executable objectcode.

Computability What can and cannot be computed.

Computingmachine

Any machine that performed the work of a human computer.

Consoleapplication

A program that runs in a text-based window into which the user types and which displays text output from the computer.

Constant A value that does not change throughout the program.


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CSV le(Comma-separatedvalues le)

A text le with one record per line and the elds of each recordseparated by commas.

Datacompression

Squeezes data into a smaller number of bytes than the datawould occupy if uncompressed.

Datacompression(Lossy

compression)

Lossy compression methods discard information which is notconsidered important.

Datacompression(Run-lengthencoding)

A simple compression technique that takes account of the factthat some images have long runs of pixels of the same colour.

Decision table A table that shows the outcome for a given logical condition.

Denary number system

A number system that uses the digits 0 to 9.

Dry-run testingTest an algorithm or program code without the use of acomputer.

Enumeratedtype

An ordered set of values.


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Evidence of testing

Something that shows the data entered and the result from theprogram (e.g. screenshot).

Exceptionhandling

Exception handling is able to recover from the error withoutcrashing the program.(Trapping errors and handling it.)

Field A variable that is part of a record.

Finite statemachine

A machine that consists of a xed set of possible states with aset of allowable inputs that change the state and a set of possible inputs.

Flow chartA diagram that shows the sequence of operations to solve a

problem.

FunctionA routine that is called as part of an expression and returns avalue.

GIGO(garbage in garbageout)

The program cannot possibly produce the correct results if theinput is invalid.

Global variableA variable declared at the beginning of the program andaccessible from anywhere in the program.


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Hand trace, deskcheck or dry run

A careful step-by-step simulation on paper of how an algorithmwould be executed by a computer.

Hexadecimalnumber system

A number system that uses the digit 0 to 9 and the letters A toF.

High-levelprogramminglanguage

A language that has English-like keywords and commands toexpress basic constructs of sequence, selection (decision) andrepetition (iteration).

Identier A unique name given to a variable, a procedure, a function, etc.

Integer A whole number.

Integer division Returns only the whole number part of a division.

Linear searchFinding a particular element in an unordered list.Scanning each element of the list in a sequential manner.

Local variablesA variable declared in a program block and accessible only withinthe program block.


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ProcedureA routine that may or may not return a value.A procedure call is a statement in its own right, not part of anexpression.

ProgramA description in a programming language of a process thatachieves some result that is useful.

PseudocodeCode that resembles a programming language but that use lessstrict syntax to express an algorithm.It is independent of any real programming language.

Real number A number with a decimal point and a fractional part.

Record A data structure that groups a number of variables.

Repetition or iteration

A step or sequence of steps that are repeated until somecondition is satised or while some condition is satised.

Resolution of aVDU screen

A quantity expressed as the number of pixels per row by thenumber of pixels per column.

Resolution of animage

A quantity expressed as the number of dots / inch / centimetre.


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Requirementsspecication

A set of system objectives.

Run-time error When the program crashes or gets stuck in a loop.

Selection A decision-making step.

SequenceConsecutive steps or groups of steps processed one after another in the order that they arise.

SetA collection of values of the same ordinal type with no associated

order.

Softwaremaintenance

Updating a program to correct faults or improve features.

Solution(Module)

A self-contained entity that results when a problem is dividedinto subproblems. Each module corresponds to a subproblem.

Solution(Stepwiserenement)

The process of breaking a problem down through successivesteps into smaller problems.


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Solution (Top-down design(Conquer or functionaldecomposition))

Breaks a problem into smaller problems that are easier to workon.

Sound(ADC)

Analogue-to-digital convertor Converts an analogue signal into an equivalent digital signal.

Sound(Analoguesignal)

An electrical signal that varies in a continuous manner.

Sound(DAC)

Digtal-to-anlogue convertor.Converts a digital signal into an equivalent signal.

Sound

(Digital data)Data that takes the form of discrete values.

Sound(MIDI)

Musical Information Digital Interface.A way of representing the sounds made by an instrument.

Sound(Nyquist'stheorem)

Sample at a frequency at least twice the rate of the highestfrequency in the sampled signal.

Sound(PCM)

Pulse Code Modulation.A process for coding sampled analogue signals by recording theheight of each sample in a binary electrical equivalent.


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Sound(Pulse amplitudemodulation )

A process that samples analogue signals at regular time intervalsand produces electrical pulses of height proportional to theoriginal signal's amplitude at the instant of sampling.

Sound(Quantisationnoise)

The di erence between the original amplitude and its sampledvalue.

Sound(Synthesisesound)

Use digital means to generate audio signals resemblinginstrument sounds or the human voice.

Sound(Analogue data)

Data that varies in a continuous manner.

Sound

(Digital signal)

An electrical signal with voltage changes that are abrupt or in

discrete steps.

State transitiondiagram

A way of describing an FSM graphically.Each state is represented by a circle and each transition by anarrow labelled with the input that causes the transition plus anyoutput resulting from the transition.

State transitiontable

Shows the e ect on the current state of an FSM of particular inputs and any corresponding output.

String A sequence of zero or more characters.


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Structure chart A hierarchy chart with interfaces and control information.

Structure tableAn indented, numbered list of steps produced by stepwiserenement.

StructuredEnglish

A very restricted subset of the English language.

System A whole composed of parts in orderly arrangement.

Systems analysis The study of a complex process in order to improve its e ciency.

Test data(Erroneous data)

Value which is not able to pass the validation check.

Test data(Boundary data)

A boundary value is a value where the processing is di erent for values below and above this value.

Test data(Normal data)

Large number of values except boundary and erroneous data.


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Test planA list of planned tests with their data or referring to a set of testdata.

Text leIt consists of a sequence of printable characters organised intolines, each of which is terminated by an end-of-line marker.

Two'scomplement

A system for representing negative numbers.

Validation checkA check made by a program to see that the data entered isreasonable.

Validation check

(Check digits)

A check digit is calculated from the other digits and appended to

the code.

Validation check(Format check)

A format check can ensure the code conforms to certain rules.

Validation check(Length check)

When processing strings you can check whether the stringlength is as expected.

Validation check(Lookup check)

User is expected to input one of a list of values which theprogram could look up this value in a list or database.


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Validation check(Presencechecks)

The presence check ensures that all required values are entered.

Validation check(Range check)

The value entered must be within a certain range.

Validation check(Type check)

Ensure the user is entering the expected type of data.

Variable A location in memory that contains one or more data values.

Variable Role

(Fixed value)

A variable initialised without any calculation and not changed

thereafter.

Variable Role(Follower)

A variable that gets its new value from the old value of someother data item.

Variable Role(Gatherer)

A variable accumulating the e ect of individual values.

Variable Role(Most recentholder)

A variable holding the latest value encountered when processinga succession of unpredictable values.Simply the latest value obtained as input.


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Variable Role(Most wantedholder)

A variable holding the most appropriate value encountered sofar.

Variable Role(Stepper)

A variable stepping through a systematic, predictable successionof values.

Variable Role(Temporary)

A variable holding some value for a short time only.

Variable Role(Transformation)

A variable that always get its new value from a xed calculationof values of other variables.

Vector graphicRecords geometric and other information about the objects that

make up an image.

Vector graphic(Drawing list)

The list of drawing commands that recreate a vector graphic.

Vector graphic(Object)

A component of a vector graphic (such as a line, a rectangle or acircle).

Vector graphic(Property)

Property of a vector graphic object describes things such as thesize, direction, thickness, shading, font size or typeface.


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White-boxtesting(structural testing)

Tests are devised to check each possible path through theprogram code.

Word A group of bytes.

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AQA COMP1 Extracted Definition