Pointers on C.pdf

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1、orcedversion1.0,byvivisimo,andpostedinhttp://library.nulastmodified:2011.06.051AQuickStart1.1IntroductionItȱisȱalwaysȱdifficultȱtoȱstartȱdescribingȱaȱprogrammingȱlanguageȱbecauseȱlittleȱdetailsȱdoȱnotȱmakeȱmuchȱsenseȱuntilȱoneȱknowsȱenoughȱtoȱunderstan

2、dȱtheȱȈbigȱpicture.ȈȱInȱthisȱchapter,ȱIȱtryȱtoȱgiveȱyouȱaȱglimpseȱofȱtheȱbigȱpictureȱbyȱlookingȱatȱaȱsampleȱprogramȱandȱexplainingȱitsȱworkingsȱlineȱbyȱline.ȱThisȱsampleȱprogramȱalsoȱshowsȱyouȱhowȱfamiliarȱproceduresȱareȱaccomplishedȱinȱC.ȱThisȱinforma

3、tionȱplusȱtheȱotherȱtopicsȱdiscussedȱinȱtheȱchapterȱintroduceȱyouȱtoȱtheȱbasicsȱofȱtheȱCȱlanguageȱsoȱthatȱyouȱcanȱbeginȱwritingȱusefulȱprograms.ȱȱTheȱprogramȱweȱdissectȱreadsȱtextȱfromȱtheȱstandardȱinput,ȱmodifiesȱit,ȱandȱwritesȱitȱtoȱtheȱstandardȱoutp

4、ut.ȱProgramȱl.lȱfirstȱreadsȱaȱlistȱofȱcolumnȱnumbers.ȱTheseȱnumbersȱareȱpairsȱandȱindicateȱrangesȱofȱcolumnsȱinȱtheȱinputȱline.ȱTheȱlistȱisȱterminatedȱwithȱaȱnegativeȱnumber.ȱTheȱremainingȱinputȱlinesȱareȱreadȱandȱprinted,ȱthenȱtheȱselectedȱcolumnsȱfro

5、mȱtheȱinputȱlinesȱareȱextractedȱandȱprimed.ȱNoteȱthatȱtheȱfirstȱcolumnȱinȱaȱlineȱisȱnumberȱzero.ȱForȱexample,ȱifȱtheȱinputȱisȱȱ491220-1abcdefghijklmnopqrstuvwxyzHellothere,howareyou?Iamfine,thanks.Seeyou!Byeȱthenȱtheȱprogramȱwouldȱproduce:ȱȱOriginalinp

6、ut:abcdefghijklmnopqxstuvwxyzRearrangedline:efghijmnopqrstuDownloadathttp://www.pin5i.com/2ȱChapter1AQuickStartOriginalinput:Hellothere,howareyou?Rearrangedline:otherhowareOriginalinput:Iamfine,thanks.Rearrangedline:fine,thanks.Originalinput:Seeyou!Rea

7、rrangedline:you!Originalinput:ByeRearrangedline:ȱTheȱimportantȱpointȱaboutȱthisȱprogramȱisȱthatȱitȱillustratesȱmostȱofȱtheȱbasicȱtechniquesȱyouȱneedȱtoȱknowȱtoȱbeginȱwritingȱCȱprograms.ȱȱȱȱȱȱȱȱȱ/***Thisprogramreadsinputlinesfromstandardinputandprints**

8、eachinputline,followedbyjustsomeportionsoftheline,to**thestandardoutput.****Thefirstinputisalintofcolumnnumbers,whichendswitha**negativenumber.Thecolumnnumbersarepairedandspecify**rangesofcolumnsfromtheinputlinethataretobeprinted.**Fore