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1、ThePCGameAdapterChapter24OneneedlooknofartherthantheinternalsofseveralpopulargamesonthePCtodiscoverthanmanyprogrammersdonotfullyunderstandoneoftheleastcomplexdevicesattachedtothePCtoday–theanaloggameadapter.Thisdeviceallowsausertoconnectuptofourresisti
2、vepotentiometersandfourdigitalswitchconnectionstothePC.ThedesignofthePC’sgameadapterwasobviouslyinfluencedbytheanaloginputcapabilitiesoftheAppleIIcomputer1,themostpopularcomputeravailableatthetimethePCwasdeveloped.AlthoughIBMprovidedfortwicetheanalogin
3、putsoftheAppleII,thinkingthatwouldgivethemanedge,theirdecisiontosupportonlyfourswitchesandfourpotentiometers(or“pots”)seemsconfiningtogamedesignerstoday–inmuchthesamewaythatIBM’sdecisiontosupport256KRAMseemssolimitingtoday.Nevertheless,gamedesignershav
4、emanagedtocreatesomereallymarvel-ousproducts,evenlivingwiththelimitationsofIBM’s1981design.IBM’sanaloginputdesign,likeApple’s,wasdesignedtobedirtcheap.Accuracyandperformancewerenotaconcernatall.Infact,youcanpurchasetheelectronicpartstobuildyourownversi
5、onofthegameadapter,atretail,forunderthreedollars.Indeed,todayyoucanpurchaseagameadaptercardfromvariousdiscountmerchantsforundereightdollars.Unfortunately,IBM’slow-costdesignin1981producessomemajorperformanceproblemsforhigh-speedmachinesandhigh-performa
6、ncegamesoftwareinthe1990’s.However,thereisnousecryingoverspilledmilk–we’restuckwiththeoriginalgameadapterdesign,weneedtomakethemostofit.Thefollowingsectionswilldescribehowtodoexactlythat.24.1TypicalGameDevicesThegameadapterisnothingmorethanacomputerint
7、erfacetovariousgameinputdevices.ThegameadaptercardtypicallycontainsaDB15connectorintowhichyoupluganexternaldevice.Typicaldevicesyoucanobtainforthegameadapterincludepaddles,joysticks,flightyokes,digitaljoysticks,rud-derpedals,RCsimulators,andsteeringwhe
8、els.Undoubtedly,thisisbutashortlistofthetypesofdevicesyoucanconnecttothegameadapter.Mostofthesedevicesarefarmoreexpensivethatthegameadaptercarditself.Indeed,certainhighperformanceflightsimulatorconsolesforthegameadaptercostseveralhundre
