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Introduction

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ObjectivesAttheendofthelesson,thestudentshouldbeableto:

IdentifythedifferentcomponentsofacomputerKnowaboutprogramminglanguagesandtheircategoriesUnderstandtheprogramdevelopmentlifecycleandapplyitinproblemsolvingLearnthedifferentnumbersystemsandtheirconversions

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Introduction

Computer

amachinethatperformsavarietyoftasksaccordingtospecificinstructions

Twomajorcomponents:

Hardware

tangiblepartofthecomputercomposedofelectronicandmechanicalpartsintangiblepartofacomputerconsistsofdataandthecomputerprograms

Software

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BasicComponentsofaComputer:Hardware

CPU

CentralprocessingunitTheprocessoristhebrainofthecomputerItdoesthefundamentalcomputingwithinthesystemExamples:Pentium,AthlonandSPARC.

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BasicComponentsofaComputer:Hardware

Memory

wheredataandinstructionsneededbytheCPUtodoitsappointedtaskscanbefound2Types:

MainMemorySecondaryMemory

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BasicComponentsofaComputer:Hardware

MainMemory

usedtoholdprogramsanddata,thattheprocessorisactivelyworkingwith.notusedforlong-termstoragesometimescalledtheRAM(RandomAccessMemory).consideredasvolatilestoragemeansoncethecomputeristurnedoff,allinformationresidinginthemainmemoryiserased

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BasicComponentsofaComputer:Hardware

SecondaryMemory

usedtoholdprogramsanddataforlongtermuse.Examplesofsecondarymemoryareharddisksandcd-rom.consideredasnon-volatilestorage

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BasicComponentsofaComputer:Hardware

Comparisonbetweenmainmemoryandsecondarymemory

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BasicComponentsofaComputer:Hardware

InputandOutputDevices

allowsacomputersystemtointeractwiththeoutsideworldbymovingdataintoandoutofthesystemExamples:

inputdevices:keyboards,miceandmicrophonesoutputdevices:monitors,printersandspeakers

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BasicComponentsofaComputer:Software

Software

aprogramthatacomputerusesinordertofunctionkeptonsomehardwaredevicelikeaharddisk,butititselfisintangibledatathatthecomputerusescanbeanythingthataprogramneeds

Programs

actlikeinstructionsfortheprocessor.

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BasicComponentsofaComputer:Software

SomeTypesofComputerPrograms

SystemsProgramsApplicationProgramsCompilers

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BasicComponentsofaComputer:Software

SystemsPrograms

ProgramsthatareneededtokeepallthehardwareandsoftwaresystemsrunningtogethersmoothlyExamples:OperatingSystemslikeLinux,Windows,Unix,Solaris,MacOS

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BasicComponentsofaComputer:Software

ApplicationPrograms

ProgramsthatpeopleusetogettheirworkdoneExamples:WordProcessor,Gameprograms,Spreadsheets

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BasicComponentsofaComputer:Software

Compilers

TranslatescomputerprogramstomachinelanguageMachinelanguage

Languagethatyourcomputerunderstands.

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ProgrammingLanguages

ProgrammingLanguage

astandardizedcommunicationtechniqueforexpressinginstructionstoacomputerLikehumanlanguages,eachlanguagehasitsownsyntaxandgrammarTherearedifferenttypesofprogramminglanguagesthatcanbeusedtocreateprograms,butregardlessofwhatlanguageyouuse,theseinstructionsaretranslatedintomachinelanguagethatcanbeunderstoodbycomputers.

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CategoriesofProgrammingLanguages

High-levelProgrammingLanguages

aprogramminglanguagethatismoreuser-friendly,tosomeextentplatform-independent,andabstractfromlow-levelcomputerprocessoroperationssuchasmemoryaccessesAprogrammingstatementmaybetranslatedintooneorseveralmachineinstructionsbyacompiler.Examples:Java,C,C++,Basic,Fortran

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CategoriesofProgrammingLanguages

Low-levelAssemblyLanguage

Assemblylanguagesaresimilartomachinelanguages,buttheyaremucheasiertoprogrambecausetheyallowaprogrammertosubstitutenamesfornumbersAssemblylanguagesareavailableforeachCPUfamily,andeachassemblyinstructionistranslatedintoonemachineinstructionbyanassemblerprogram

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CategoriesofProgrammingLanguages

NOTE:

Theterms"high-level"and"low-level"areinherentlyrelative.Originally,assemblylanguagewasconsideredlow-levelandCOBOL,C,etc.wereconsideredhigh-level.Manyprogrammerstodaymightrefertotheselatterlanguagesaslow-level

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ProgramDevelopmentLifeCycle

Basicstepsintryingtosolveaproblemonthecomputer:1.ProblemDefinition2.ProblemAnalysis3.Algorithmdesignandrepresentation(Pseudocodeorflowchart)4.Codinganddebugging

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1.ProblemDefinition

Aclearlydefinedproblemisalreadyhalfthesolution.Computerprogrammingrequiresustodefinetheproblemfirstbeforeweeventrytocreateasolution.Letusnowdefineourexampleproblem:Createaprogramthatwilldeterminethenumberoftimesanameoccursinalist.

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2.ProblemAnalysis

Aftertheproblemhasbeenadequatelydefined,thesimplestandyetthemostefficientandeffectiveapproachtosolvetheproblemmustbeformulated.Usually,thisstepinvolvesbreakinguptheproblemintosmallerandsimplersubproblems.ExampleProblem:

Determinethenumberoftimesanameoccursinalistlistofnames(let'scallthisnameList)nametolookfor(let'scallthiskeyName)thenumberoftimesthenameoccursinalistIntroductiontoProgramming121

Inputtotheprogram:

Outputoftheprogram:

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3.AlgorithmDesignandrepresentation

Algorithm

aclearandunambiguousspecificationofthestepsneededtosolveaproblem.Itmaybeexpressedineither:

Humanlanguage(English,Tagalog)GraphicalrepresentationlikeaflowchartPseudocode-whichisacrossbetweenhumanlanguageandaprogramminglanguage

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3.AlgorithmDesign&representationHumanLang.

ExpressingoursolutionthroughHumanlanguage:1.Getthelistofnames,let'scallthisnameList2.Getthenametolookfor,let'scallthisthekeyname3.ComparethekeynametoeachofthenamesinnameList4.Ifthekeynameisthesamewithanameinthelist,add1tothecount5.Ifallthenameshavebeencompared,outputtheresult

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3.AlgorithmDesignandrepresentation-Flowchart

Expressingoursolutionthroughaflowchart:

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FlowchartSymbols

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FlowchartSymbols

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FlowchartSymbols

NOTE:

Thesearejustguidelinesforcommonlyusedsymbolsincreatingflowcharts.Youcanuseanysymbolsincreatingyourflowcharts,aslongasyouareconsistentinusingthem

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3.AlgorithmDesignandrepresentation-Pseudocode

Expressingoursolutionthroughpseudocode:LetnameList=ListofNamesLetkeyName=thenametobesoughtLetCount=0ForeachnameinNameListdothefollowingifname==keyNameCount=Count+1

DisplayCount

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4.CodingandDebugging

Afterconstructingthealgorithm,itisnowpossibletocreatethesourcecode.Usingthealgorithmasbasis,thesourcecodecannowbewrittenusingthechosenprogramminglanguage.Debugging

Theprocessoffixingsomeerrors(bugs)inyourprogram

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TypesofErrors

Compile-timeerrororsyntaxerrors

occurifthereisasyntaxerrorinthecode.Thecompilerwilldetecttheerrorandtheprogramwon'tevencompile.Atthispoint,theprogrammerisunabletoformanexecutableprogramthatausercanrununtiltheerrorisfixed.

RuntimeErrors

Compilersaren'tperfectandsocan'tcatchallerrorsatcompiletime.Thisisespeciallytrueforlogicerrorssuchasinfiniteloops.Thistypeoferroriscalledruntimeerror.

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NumberSystems

Numberscanberepresentedinavarietyofways.TherepresentationdependsonwhatiscalledtheBASE.Youwritethesenumbersas:Numberbase

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NumberSystems

Thefollowingarethefourmostcommonrepresentations.

Decimal(base10)

CommonlyusedValiddigitsarefrom0to9Example:12610(normallywrittenasjust126)Validdigitsare0and1Example:11111102

Binary(base2)

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NumberSystems

Thefollowingarethefourmostcommonrepresentations.(continuation)

Octal(base8)

Validdigitsarefrom0to7Example:1768Validdigitsarefrom0to9andAtoF(orfromatof)Example:7E16

Hexadecimal(base16)

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NumberSystems

Examples:

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Conversion:DecimaltoBinary

Method:

continuouslydividethenumberby2gettheremainder(whichiseither0or1)getthatnumberasadigitofthebinaryformofthenumbergetthequotientanddividethatnumberagainby2repeatthewholeprocessuntilthequotientreaches0or1wethengetalltheremaindersstartingfromthelastremainder,andtheresultisthebinaryformofthenumberNOTE:Forthelastdigitwhichisalreadylessthanthedivisor(whichis2)justcopythevaluetotheremainderportion.

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Example:DecimaltoBinary

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Conversion:BinarytoDecimal

Method:

wemultiplythebinarydigitto"2raisedtothepositionofthebinarynumber"Wethenaddalltheproductstogettheresultingdecimalnumber.

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Example:BinarytoDecimal

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Conversion:DecimaltoOctal/Hexadecimal

Method:

ConvertingdecimalnumberstoOctalorhexadecimalisbasicallythesameasconvertingdecimaltobinary.However,insteadofhaving2asthedivisor,youreplaceitwith8(foroctal)or16(forhexadecimal)

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Example:DecimaltoOctal/Hexadecimal

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Conversion:Octal/HexadecimaltoDecimal

Method:

Convertingoctalorhexadecimalnumbersisalsothesameasconvertingbinarynumberstodecimal.Todothat,wewilljustreplacethebasenumber2with8forOctaland16forhexadecimal.

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Example:Octal/HexadecimaltoDecimal

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Conversion:BinarytoOctal

Method:

partitionthebinarynumberintogroupsof3digits(fromrighttoleft)paditwithzerosifthenumberofdigitsisnotdivisibleby3converteachpartitionintoitscorrespondingoctaldigitThefollowingisatableshowingthebinaryrepresentationofeachoctaldigit.

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Example:BinarytoOctal

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Conversion:OctaltoBinary

Method:

Convertingoctalnumberstobinaryisjusttheoppositeofwhatisgivenpreviously.Simplyconverteachoctaldigitintoitsbinaryrepresentation(giventhetable)andconcatenatethem.Theresultisthebinaryrepresentation.

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Example:OctaltoBinary

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Conversion:BinarytoHexadecimal

Method:

partitionthebinarynumberintogroupsof4digits(fromrighttoleft)paditwithzerosifthenumberofdigitsisnotdivisibleby4converteachpartitionintoitscorrespondinghexadecimaldigitThefollowingisatableshowingthebinaryrepresentationofeachhexadecimaldigit

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Example:BinarytoHexadecimal

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Conversion:HexadecimaltoBinary

Method:

Convertinghexadecimalnumberstobinaryisjusttheoppositeofwhatisgivenpreviously.Simplyconverteachhexadecimaldigitintoitsbinaryrepresentation(giventhetable)andconcatenatethem.Theresultisthebinaryrepresentation.

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Example:HexadecimaltoBinary

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Summary

BasicComponentsofaComputer

HardwareSoftwareWhatisaProgrammingLanguage?CategoriesofProgrammingLanguages1.ProblemDefinition2.ProblemAnalysis3.AlgorithmDesignandrepresentation(humanLang.,Flowchart,Pseudocode)4.CodingandDebuggingIntroductiontoProgramming151

OverviewofComputerProgrammingLanguages

ProgramDevelopmentLifeCycle

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Summary

TypesofErrors

Compiletimeerrors/syntaxerrorsRuntimeerrorsDecimal,Hexadecimal,Binary,OctalConversions

NumberSystems

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