JOYTemplate for Footer group  hXS%kIz k phlI Y%z kZ-KiZ-K N"զI` {x R< N"զI` {x R<L$ЦIz yx UL$ЦIz xx UL$ЦIz x UL$ЦIz ~x UL$ЦIz }x UL$ЦIz |x UL$ЦIz sx UL$ЦIz rx UModern ++Y"ټKۺ[X۹:ѩںRj}[Yq˫˻"wDd9r99̷ܻۛYgͻںۻɫۻʘ٩۫٘ xScript 1: 0x R<  0MONITORPROGRAMx xScript 1: 0x R<  &KPage=== :(c)copyright1989byGeoffBuckeridge xScript 1: 0x R<  MONITORPROGRAM(cont)x xScript 1: 0x R<  &KPage=== :(c)copyright1989byGeoffBuckeridge xScript 1: 0x R< TheMONITORprogramdescribedhereiswrittenin'C'andenablesyoutolookat  any'block'ofmemorywhereveritis'paged'intothesystem.Itisaread-only  H1monitor,unliketheoneIwroteforthe'April1988editionofComputingwith ! theAmstradPCW'.ThisonewaswritteninBASICbutallowedyoutoaltertheZcontentsofanymemorylocation. lUForthoseofyouwhoareunabletoseeacopyofthismagazine,thenext  :#threeparagraphsexplain'memorypagingandblockswitching.Ialsoreferyouto'TheAmstradCP/MPlusbyDavidPowysLybbeandAndrewR.M.Clarke. 5TheZ80,asweknow,isonlycapableofaddressingupto64Kofmemory,and yetwealsoknowthatthePCWcanhaveeither256Kor512Kfittedas  standard.So,howisallthisextramemoryaccessed,andhowcanwestudyitscontentsorchangeit. qZThesecretliesintheterm"MemoryPaging".InthePCW,the64Kaddress rangeisdividedintofour16Kpages.The256Kor512Kofphysicalmemoryis  F/alsosplitinto16Kchunks,knownasblocks."MemoryPaging"then,describesatheabilitytoswitchdifferentmemoryblocksintodifferentaddresspages. Say,forexample,atpower-onblocks0,1,2&3areswitchedintopages0,1, n2&3,andlateron,youwanttouseblock14.Itissimplyamatterof  3swappingoneofyourpreviouslyselectedblocksfornumber14.Forinstance, ! youcouldnowhaveblocks0,1,14&3selected.Block14thenreplacesBlock  T=2,appearstobeinaddressrange8000-BFFF(Hex),andcanbereadeither  fromamachinecodeprogram,orusingtheBASICPEEKstatement.Inpractice,  G0onthePCWthetoppageofmemory,page3addressingC000-FFFF(Hex),will >'alwaysselectblock7.ThiscommonRAMareacanbeusedtostoreprogramsin,sothatyouwillalwaysknowwheretofindthemagain.d xScript 1: 0x R<   ToinvoketheMONITOR,simplytypeMONITORattheCP/Mpromptandtheinstructionsaredisplayed.