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AS Computing Unit 1

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23321740ComputingThe study of natural and artificial information processes
23321741Computationthe process of calculating or determining something by mathematical, logical or interactive methods
23321742AbstractionHow to communicate complex ideas simply and how to decompose problems logically
23321743Automationturning an algorithm into a computer program
23321744Algorithma description, independent of any programming language, of a process that achieves some task. It is a step by step procedure for solving a problem
23321745SequenceConsecutive steps processed in that order
23321746AssignmentOperation that assigns a value to a variable
23321747SelectionA decision making step
23321748RepititonSequence repeated until a condition is met
23321749Dry RunA step by step simulation on paper showing how an algorithm would be executed recording changing values of variables
23321750IntegerA whole number
23321751ByteAn unsigned integer from 0 to 255
23321752RealA number with a fractional part
23321753BooleanCan be True or False
23321754Charactera single character
23321755Stringa sequence of characters
23321756Date/timeStored as a real number
23321757EnumeratedAn ordered set of values
23321758Subrangerange of values within a type eg. capital letters
23321759Setcollection of values of the same type with no order
23321760RecordData Structure that groups a number of variables
23321897Fixed ValueInitialised without calculation, not changed
23321898StepperSteps through a systematic succession of values
23321899Most Recent HolderHolds the latest value encountered
23321900Most Wanted HolderMost appropriate value met so far is held
23321901GathererAccumulates the effect of individual values
23321902TransformationGets its value from fixed calculation of other variables
23321903FollowerTakes the old value of another variable
23321904Variablelocation in memory that contains a data value
23321905identifiera unqiue name given to a variable / procedure
23321906Global VariableDeclared at start, accessibile anywhere
23321907Local Variabledeclared and accessible in one procedure only
23321908ConstantValue does not change throughout program, makes program easier to understand and maintain
23321909ParameterValue passed into and out of a procedure
23321910InterfaceList of parameters when calling a procedure
23321911Call By Valuea copy of the value of the variable used is passed to the procedure
23321912Call By ReferenceProcedure accesses (and changes) actual variable used
23321913ArrayOrdered Set of values of the same data type, grouped together and referred to by a single identifier
23321914IndicesAre used to refer to individual array elements
23321915Text FileA sequence of printable characters organised line by line
23321916CSV FileText File, each field of a record is seperated by commas
23321917Binary FileCan include numbers which cannot be displayed in a text editor
23321918ValidationChecking that the data entered is reasonable
23321919Range CheckValue must be within a certain range
23321920Format CheckValue conforms to rules
23389562Length CheckLength of string does not exceed maximum
23389563Type CheckInput as string, try to convert to desired data type eg. integer
23389564Lookup CheckValue has to appear on a known list
23389565Check DigitCalculated from other digits and appended to code
23389566Prescence CheckSomething must be entered
23389567Denary NumbersBase 10
23389568Binary NumbersBase 2
23389569HexadecimalShorthand for binary, easier for humans to understand
23389570Two's ComplimentMost significant bit is negative
23389571ASCIIuses 7 bits
23389572UNICODEUses 16 bits so can represent more symbols than ASCII
23389573Hamming CodeExtra parity bits so can correct error
23389574Single Bit ParityReciever checks parity after transmission, Two errors are not detected
23389575Gray CodeBinary representation where consecutive values differ in only 1 bit
23389576Gray Code +More reliable system & counter consumes less power
23389577Gray Code -Used in angular movement systems with different clock frequencies
23389578PixelThe Smallest addressable area in an image
23389579BitmapPixels are mapped to positions in memory that store binary codes for colour of each pixel
23389580Screen ResolutionNumbers of pixels in rows and columns
23389581Image ResolutionNumber of pixels per inch
23389582Colour depthBits needed to store each pixel
23389583Image File SizeRows x Columns x Colour Depth
23389584Vector GraphicsIdentifies objects that make up an image
23389585PropertyDescribes size, direction, thickness etc
23389586Drawing ListList of commands that recreate a graphic
23389743Vector Graphic +Geometric images take up less memory, Scale without distortion & are easier to edit
23389744Data CompressionReduces the number of bytes used by a file
23389745Run-length encodingEncode a run of pixels of same colour as 2 bytes storing number of pixels and colour code
23389746Lossy CompressionDiscards less important information eg. reduces backgroudn resolution
23389747Analogue DataVaries in a continous manner
23389748Analogue SignalElectrical form of analogue data
23389749ADCSamples analogue signal at regular intervals and converts to a value propotional to amplitude of signal
23389750Nyquist's TheoremSample at a frequency atleast twice the rate of the highest frequency in the sample's signal
23389751Synthesised SoundDigitally generated audio that resembles the human voice or instruments
23389752TestingUsed to reveal the prescence of errors
23389753Black Box testingUse test data and compare with expected results
23389754White Box TestingCheck each path through the code for errors
25282566Top Down DesignBreaks a problem into smaller problems which are easier to work on
25282567Finite State MachineConsists of a fixed set of possible states, a set of possible inputs and a set of possible outputs
25282568State Transition TablesShow the effect on the current state of particular inputs
25282569PseudocodeA way of expressing an algorithm which uses less strict syntax than a program
25282570Structured EnglishA way of expressing an algorithm which uses a very restricted subset of language
25282571Structure TableAn indented numbered list of steps produced by stepwise refinement
25282572Hierarchy ChartShows levels of subroutines

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