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1、Chapter11BitOperationInordertosavememoryspace,severalstatussignsareusuallyputtogetherintoonebyte(orbit).Clanguageisdesignedforstudyingsystemsoftware,soitoffersbitoperationwhichseparatestatussignfromsignbytememory.Bitoperationisthatwedoitinbinary.11.1numb
2、erexpressedincomputer11.2bitoperation11.3bitsegment11.1NumberExpressedinComputer1.BitandByte Memoryincomputersystemisconstitutedofmanynamedbyteunits.Onebyteismadeupofeightbits,andthevalueis0or1ofeverybit.Thebitintherightsideiscalled“thelowestbit”,anditsn
3、umberis0.Thebitintheleftsideiscalled“thehighestbit”,andsetthenumbertoeachbitfromthelowesttohighestinorder.Diagram11-1isthenumberofeachbitinonebyte.Fig11-1Thenumberofeachbitinonebyte2.DigitExpressedbyInitialCodeDigitexpressedbyinitialcodeisthatusingthehig
4、hestbitasasignbit(0referstopositivenumber,1referstonegativenumber),theotherbitsrepresenttothemselves’absolutevalue(expressedinbinary).Inordertosimpledescription,weuseonebytetoexpressoneintegralinthisclass.76543210Forexample,theinitialcodeof+9is00001001└→
5、signbit0referstopositivenumbertheinitialcodeof-9is10001001。└→signbit0referstonegativenumber3.DigitExpressedbyOppositeCodedigitexpressedbyoppositecodeincludestwocircumstances:（1）oppositecodeofpositivenumber:thesameastheinitialcode.Forexample,theoppositeco
6、deof+9is00001001。（2）oppositecodeofnegativenumber:signbitis1,otherbitsisoppositetotheirabsolutevalue(1turnsto0,0turnsto1).Forexample,theoppositecodeof-9is:becauseitisanegativenumber,signbitis1;othersevenbitsistheoppositeofitsabsolutevaluethattheinitialof+
7、9,sotheoppositeof-9is11110110.4.DigitExpressedbyComplementCodeDigitexpressedbycomplementcodealsoincludestwocircumstances:（1）thecomplementcodeofpositivenumber:thesameastheinitialcode.Forexample,thecomplementcodeof+9is0001001.（2）thecomplementofnegativenumb
8、er:signbitis1,otherbitsisoppositetotheirabsolutevalue’sinitialcode,thenadd1.Forexample,thecomplementcodeof-9is:becauseitisanegativenumber,signbitis1,othersevenbitsistheoppositeofitsabsolutevaluethattheinitialof+9,sotheoppo
