ComputerSystems:AProgrammersPerspective

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ComputerSystems:AProgrammer'sPerspective

Instructor'sSolutionManual 1 RandalE.Bryant DavidR.O'Hallaron December4,2003 1 Copyrightc

2003,R.E.Bryant,D.R.O'Hallaron.Allrightsreserved. 2 / 4

Chapter1 SolutionstoHomeworkProblems

Thetextusestwodifferentkindsofexercises:

PracticeProblems.Theseareproblemsthatareincorporateddirectlyintothetext,withexplanatory solutionsattheendofeachchapter.Ourintentionisthatstudentswillworkontheseproblemsasthey readthebook.Eachonehighlightssomeparticularconcept.

HomeworkProblems.Thesearefoundattheendofeachchapter.Theyvaryincomplexityfrom simpledrillstomulti-weeklabsandaredesignedforinstructorstogiveasassignmentsortouseas recitationexamples.Thisdocumentgivesthesolutionstothehomeworkproblems.

1.1Chapter1:ATourofComputerSystems

1.2Chapter2:RepresentingandManipulatingInformation

Problem2.40Solution:

Thisexerciseshouldbeastraightforwardvariationontheexistingcode.code/data/show-ans.c 1voidshow_short(short intx) 2{

• show_bytes((byte_pointer) &x,sizeof(shortint));

4} 5 6voidshow_long(longintx) 7{

• show_bytes((byte_pointer) &x,sizeof(long));

9}

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2CHAPTER1.SOLUTIONSTOHOMEWORKPROBLEMS

10 11voidshow_double(double x) 12{ 13 show_bytes((byte_pointer) &x,sizeof(double)); 14} code/data/show-ans.c

Problem2.41Solution:

Therearemanywaystosolvethisproblem.Thebasicideaistocreatesomemultibytedatumwithdifferent valuesforthemostandleast-signicantbytes.Wethenreadbyte0anddeterminewhichbyteitis.Inthefollowingsolutionistocreateanintwithvalue1.Wethenaccessitsrstbyteandconvertittoan int.Thisbytewillequal0onabig-endianmachineand1onalittle-endianmachine.code/data/show-ans.c 1intis_little_endian(void) 2{

3 /*MSB=0,LSB=1*/

• intx=1;

5

• /*ReturnMSBwhenbig-endian,LSBwhenlittle-endian*/
• return(int)(*(char*)&x);

8} code/data/show-ans.c

Problem2.42Solution:

Thisisasimpleexerciseinmaskingandbitmanipulation.Itisimportanttomentionthat˜0xFFisaway togenerateamaskthatselectsallbuttheleastsignicantbytethatworksforanywordsize.(x&0xFF)|(y&˜0xFF)

Problem2.43Solution:

Theseexercisesrequirethinkingaboutthelogicaloperation!inanontraditionalway.Normallywethink ofitaslogicalnegation.Moregenerally,itdetectswhetherthereisanynonzerobitinaword.A.!!x B.!!˜x C.!!(x&0xFF) D.!!(˜x&0xFF)

Problem2.44Solution:

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