CWSS Prelim P1 MS

COMMONWEALTHSECONDARYSCHOOLPRELIMINARYEXAMINATION2024 COMPUTINGPaper1MarkScheme(Theory) Name:___________________________________( ) Class:___________ SECONDARYFOUREXPRESS Wednesday28August2024SECONDARYFIVENORMALACADEMIC7155/01 1130–13302hours READTHESEINSTRUCTIONSFIRST Writeyourname,indexnumberandclassonalltheworkyouhandin.Writeindarkblueorblackpen.YoumayuseanHBpencilforanydiagramsorgraphs.Donotusestaples,paperclips,glueorcorrectionfluid. Approvedcalculatorsareallowed.Candidateswillansweronthequestionpaper. Answerallquestions. Thenumberofmarksisgiveninbrackets[]attheendofeachquestionorpartquestion.Youshouldshowallyourworking.Thetotalnumberofmarksforthispaperis80. ForExaminer’sUse Total 80 Thispaperconsistsof13printedpagesincludingthecoverpage.[Turnover

2 1 Acompanydealingwithdigitallocksusesastandardtouchscreenkeypadforitscustomerstoentertheir4-digitpincodestounlockthelocks.(a) Statetworeasonswhythepincodescanbeeasilystolen. 1Fingerprintsfromthetouchscreencanbetracedandusedtoguessthe combination. 24-digitpincodescanbeeasilyfoundthroughguessandcheckalgorithms .......................................................................................................................... [2] (b) Suggesttwowaystoprotectthepincodesfrombeingstolen. 1Useadynamictouchscreenkeypadwhichchangesthelocationsofthe digiteverytime. 2Increasethenumberofdigitsinthepincodetoincreasethenumberof combinations [2] Thecompanyprovidesanonlineserviceforcustomerswhoforgettheirpincodestologintothesystemtoresettheirpincodes. (c) Describethedifferencebetweenauthenticationandauthorisation. Authenticationistheprocessofverifyingtheidentityofauserwhileauthorisationcontrolstheuser’saccesstodataandresources.Authorisationoccursonlyafterauthenticationiscleared. [2] (d) Explainwhyauthenticationisimportantforthisserviceandsuggestonemethodtoenhancetheauthentication. Authenticationhelpstopreventunauthorisedaccesstothesystemandresetthepincodesoftheactualcustomer.Onemethodincludes:passwords,multiple-factorauthentication,securitytokensorbiometrics(Anyone) [2]

3 2 DuringCOVID-19,aruraltownhastousevideo-conferencingserviceformedicalconsultation.Thisincludespatientswholiveinnearbymountainousareas. Describeapositive,negativeandethicalimpactofintroducingthisservice. Positive Patientsinremoteplacesorlimitedmobilityareabletodoe-consultationsandgetdiagnosed.(Accepthackingintovideo-conferencing,retrievingimportantdataduringconferencingandlackofinternetaccessleadingtobeingunabletovideo-conference.DonotacceptAI,3-Dprintingtechnologyorareaofgrowthintechnologyorhackingofsystemandretrievingthemedicaldataasithasnothingtodowithvideo-conferencing) Negative Somepatientsmaypreferthepersonalapproachtomedicineanddistrustthediagnosisgiventhroughe-consults.(Donotacceptmisuseofinformationfrominternetordecreaseinjobs) Ethical Istheservicesafeorisitoktobemonitoredbyunauthorisedpersonnelsuchassystemsadministrators?(Donotacceptrobotsreplacinghumans) [3] 3 Asystemchecksifaplantisgrowinghealthilybycheckingthenumberofdaysithasgrownanditscorrespondingheight. (a) Identifyoneinputtothesystemanditsdatatype. Numberofdays,integer;heightofplant,float(Anyone) [1](b) Identifyoneoutputtothesystemandwriteaprogramcodetoproducetheoutput. Output Healthstatusofplant Programcode print("Theplantisgrowinghealthily.")[1] Thesystemisupgradedtocheckthehealthstatusofanynumberofplants. (c) Identifyaproblem-solvingtechniquethatcanbeusedtomodifytheprogramcode. Generalisation [1]

4 4 (a) Completethetruthtableforthefollowinglogiccircuit. A B C WorkingSpace XANORB BORC0 0 0 1 0 0 0 0 1 1 1 1 0 1 0 0 1 0 0 1 1 0 1 0 1 0 0 0 0 0 1 0 1 0 1 0 1 1 0 0 1 0 1 1 1 0 1 0 [3] (b) Drawalogiccircuitfortheexpression: X=(AORNOTB)NAND(NOTAANDC) [5]

5 5 Asoftwaredeveloperistaskedtodevelopacomputergameforteenagers. (a) Inthedevelopmentofhisgame,hefollowsasetofstages.Otherthanthewritingofcode,statetwootherstages. 1Gatherrequirements Plansolutions Testandrefinecode Deploycode (Anytwo) [2] (b) Theusersofthegamemusthaveausernameandpasswordtologintothegame. Thepasswordmustcontainatleast:● 12characters● 1lower-caseletter● 1upper-caseletter Writeanalgorithm,usingaflowchart,totakethepasswordasinput,repeatedly,untilitisvalidorinvalidforthreetimes.

6 [6](c) Completethetablebyidentifyingtwotypesofchecksusedin(b)andsuggestapasswordthatwilltesttheerrorconditionsofeachcheck. Typeofcheck Password lengthcheck Abc formatcheck abcdefghij (1m/row) [2] 6 Rahimissettingupacomputeratacomputershop. (a) Theowneradviseshimtopurchaseamulti-coreprocessorasadual-coreprocessorwillruntwiceasfastwhileaquad-coreprocessorwillrunfourtimesfasterthanasingle-coreprocessor. Statewhethertheowner’sstatementistrueandexplainyourreason. Theowner’sstatementisfalseasthecoresneedtocommunicatewitheachotherthroughchannelsandthususesupsomeofthespeed [2] (b) Rahimwantstopurchaseasecondarystoragedevice.Statetwofactorsthatheshouldconsiderwhilepurchasingasecondarystoragedevice. Capacity,speed,portability,durability,cost(Anytwo) [2](c) Rahimdecidedtopurchaseasolidstatestoragedevice.Statetwoexamplesofsolidstatestoragedevices. Memorycards,securedigital(SD)cards,thumbdrives,solidstatedrive(SSD) (Anytwo) [2]

7 7 Aprogramiswrittenforacashierofamini-mart.Theprogramallowstheusertoinputthepriceofitemsboughtbyacustomer,calculatestheamounttopayindollarsandtothenearestcents,andoutputsthenumberofitemsboughtandthechange.TheamounttopayincludesanadditionalGoodsandServicesTax(GST)of9%ofthepriceofeachitem. 01 more_items="Y" 02 num_items=0 03 total_price= 0 04 while(more_items="Y"): 05 price=float(input("Enterthepriceoftheitem:$")) 06 total_price= total_price+price 07 num_items=num_items+1 08 more_items=input("Anymoreitems?'Y'or'N':") 09 total_GST=1.09* price 10 print("-----------------------------------") 11 print("Pleasepay$"+ (round(total_GST,2))) 12 money_tendered=float(input("Entercashtendered:$")) 13 whilemoney_tendered> total_GST: 14 print("Cashnotenoughtopayforitems") 15 money_tendered=float(input("Entercashtendered:$")) 16 print("-----------------------------------") 17 change=money_tendered- total_GST 18 print("Itemsbought:",num_items) 19 print("Change:$"+str(round(Change,2))) (a) Theprogramhasfiveerrors. Givethelinenumberofeacherrorandwritethecorrectlineforeach. Linenumber...............4.................................................................................... Correction........while(more_items==“Y”):........ Linenumber..............9..................................................................................... Correction........total_GST=1.09*total_price.............. Linenumber.............11.................................................................................... Correctionprint("Pleasepay$"+str(round(total_GST,2))) Linenumber............13.................................................................................... Correction..whilemoney_tendered< total_GST:.. Linenumber............19..................................................................................... Correctionprint("Change:$"+ str(round(change,2)))[5]

8 (b) Statetworeasonsforusingconstantsinaprogram.1 Constantsprotectusersfromaccidentallychangingtheirvaluessomewhereinthecode. 2Constantsaredeclaredonceandcanbeusedoverandoveragainthroughouttheprogram. [2] (c) TheprogramusesaWHILE…ENDWHILEloop. StateoneothertypeofloopandexplainwhenitisusedoveraWHILE…ENDWHILEloop. FORloopisusedforrepeatingasetofstepsusingacounter.TheFORcommandgoesthroughthevaluesinasequenceusingavariableandrepeatsthesetofstepsbetweenFORandNEXTforeachvalue.ItisusedoverWHILE…ENDWHILEloopwhenthenumberofrepetitionsisknownbeforehand. [3] (d) Explainonedifferencebetweenacompilerandaninterpreter. Thecompilertranslatessourcecodetomachinecodebeforerunningcompiledprogrambuttheinterpretertranslatesthesourcecodetomachinecodewhiletheinterpretedprogramisrunning. Thecompilerproducesanexecutablefilethatmakesuseofthecompiledmachinecode.Theinterpreterperformson-the-spottranslationordetermineswhichpartofitsownmachinecodetorun. Thecompil