Computer Organization 33

CS33:

Computer Organization

SomenotesadoptedfromBryantandOHallaron

GlennReinman4731GBoelter Hall

[email protected]

Course Components Lectures

Higherlevelconcepts

Discussions Appliedconcepts,importanttoolsandskillsforlabs,clarificationoflectures,examcoverage

Labs Theheartofthecourse Provideindepthunderstandingofanaspectofsystems Programmingandmeasurement

More Info Web

ClasswebpagehostedbyCourseWeb Copiesoflectures,assignments,exams,solutions Forum

OfficeHours Textbook

RandalE.BryantandDavidR.OHallaron.ComputerSystems:AProgrammersPerspective,2nd Edition,PrenticeHall2010.

Grading Exams(45%)

Twoinclassexams(15%each) Final(15%) Allexamsareopenbook/opennotes.

Labs(50%) 5labs(10%each) Youmustworkaloneonalllabs

Homework(5%) 5assignments(1%each) Electronicsubmissiononly

Week M T W R F

1 Intro+BitsandBytes(1,2) Integers(2)

2 MachineLevelRep(3) MachineLevelRep(3) DataLabDue

3 HW#1Due MachineLevelRep(3) MachineLevelRep(3)

4 HW#2Due MachineLevelRep(3) Exam#1 BombLabDue

5 HW#3Due FloatingPoint(2) CodeOptimization(5)

6 Concurrency(12+handouts) Memory(6) BufferLabDue

7 HW#4Due Concurrency(12+handouts) Exam#2

8 Concurrency(12+handouts) I/O(10) OpenMP LabDue

9 HW#5Due VirtualMemory(9) Linking+Exceptions(7,8)

10 MIPS(handouts) Review CUDALabDue

Tentative Calendar

HomeworkandLabsDueviaCourseWeb byMidnight

Cheating Whatischeating?

Sharingcode:eitherbycopying,retyping,lookingat,orsupplyingacopyofafile.

WhatisNOTcheating? Helpingothersusesystemsortools. Helpingotherswithhighleveldesignissues. Helpingothersdebugtheircode.

Penaltyforcheating: AtthediscretionoftheAssociateDean

Lab Facilities SEASAdministeredLinuxMachine

lnxsrv.seas.ucla.edu

Remoteaccessonly Usessh tologinwithyourSEASaccount

PleasedirectanyaccountissuestotheSEAShelpdeskastheyaretheonlyoneswithrootaccessonthismachine

Alternatives(NotRecommended) Youmayuseotheralternativestodevelopyourcode BUT:WewilltestontheSEASmachines

Yourcodemustworkcorrectlyonthesemachinesforcredit

Course Theme Abstractionisgood,butdontforgetreality! Abstractionshavelimits

ThingsaremorecomplexinhardwarethantheylookinC/Java!! Bugsarehardtotrack/understandiflookingonlyfromahighlevelpointofview

Usefuloutcomes Becomemoreeffectiveprogrammers

Abletofindandeliminatebugsefficiently Abletotuneprogramperformance

PrepareforlatersystemsclassesinCS Compilers,OperatingSystems,Networks,ComputerArchitecture,ParallelProgramming

The Compilation System#includeint main(){printf(hello,world\n);

}

Pre-processor

(cpp)hello.i Compiler

(cc1)hello.s Assembler

(as)hello.o Linker

(ld)hellohello.c

Sourceprogram

(text)

Modifiedsource

program(text)

Assemblyprogram

(text)

Relocatableobject

programs(binary)

Executableobject

program(binary)

printf.o

SomenotesadoptedfromBryantandOHallaron

Bits and Bytes

Chapter2ofB&O

Why Dont Computers Use Base 10? Base10NumberRepresentation

Thatswhyfingersareknownasdigits Naturalrepresentationforfinancialtransactions

Floatingpointnumbercannotexactlyrepresent$1.20

Evencarriesthroughinscientificnotation 1.5213X104

ImplementingElectronically Hardtostore

ENIAC(Firstelectroniccomputer)used10vacuumtubes/digit

Hardtotransmit Needhighprecisiontoencode10signallevelsonsinglewire

Messytoimplementdigitallogicfunctions Addition,multiplication,etc.

Binary Representations Base2NumberRepresentation

Represent1521310 as111011011011012 Thats1x20+0x21 +1x22 +1x23 +0x24 +

ElectronicImplementation Easytostorewithbistable elements Reliablytransmittedonnoisyandinaccuratewires

0.0V

0.5V

2.8V

3.3V

0 1 0

Byte-Oriented Memory Organization ProgramsRefertoVirtualAddresses

Conceptuallyverylargearrayofbytes Actuallyimplementedwithhierarchyofdifferentmemorytypes Systemprovidesaddressspaceprivatetoparticularprocess

Programbeingexecuted Programcanclobberitsowndata,butnotthatofothers

Compiler+RunTimeSystemControlAllocation Wheredifferentprogramobjectsshouldbestored Inanycase,allallocationwithinsinglevirtualaddressspace

Encoding Byte Values Byte=8bits

Binary 000000002 to 111111112 Decimal: 010 to 25510 Hexadecimal 0016 to FF16

Base16numberrepresentation Usecharacters0to9andAtoF WriteFA1D37B16 inCas0xFA1D37B

Or0xfa1d37b

0 0 00001 1 00012 2 00103 3 00114 4 01005 5 01016 6 01107 7 01118 8 10009 9 1001A 10 1010B 11 1011C 12 1100D 13 1101E 14 1110F 15 1111

Machine Words MachineHasWordSize

Nominalsizeofintegervalueddata Includingaddresses

32bitSystems(4bytes) Limitsaddressesto4GB Becomingtoosmallformemoryintensiveapplications

64bitSystems(8bytes) Potentiallyaddress 1.8X1019 bytes x8664machinessupport48bitaddresses:256Terabytes

Machinessupportmultipledataformats Fractionsormultiplesofwordsize Alwaysintegralnumberofbytes

Word-Oriented Memory Organization

Wordsarechunksofbits AddressesSpecifyByteLocations Addressoffirstbyteinword

Addressesofsuccessivewordsdifferby4(32bit)or8(64bit)

000000010002000300040005000600070008000900100011

32-bitWords

Bytes Addr.

0012001300140015

64-bitWords

Addr =??

Addr =??

Addr =??

Addr =??

Addr =??

Addr =??

0000

0004

0008

0012

0000

0008

Data Representations SizesofCObjects(inBytes)

CDataType Typical32bit IA32 x8664 char 1 1 1 short 2 2 2 int 4 4 4 long 4 4 8 longlong 8 8 8 float 4 4 4 double 8 8 8 longdouble 8 10/12 10/16 char* 4 4 8

Oranyotherpointer

#include int main() {

printf ("%lu %lu %lu\n", sizeof(int), sizeof(long), sizeof(char*));}

Byte Ordering Howshouldbyteswithinmultibytewordbeorderedinmemory?

Conventions OlderSuns,PowerPCsareBigEndianmachines

Leastsignificantbytehashighestaddress

x86sareLittleEndianmachines Leastsignificantbytehaslowestaddress

SPARCV9,MIPS,AlphaareBiEndianmachines CanappeartobeconfigurableasBigorLittleEndian

Internalsmaystillbeonewayortheotherthough

Byte Ordering Example BigEndian(naturallanguage,M68k,IBMPower)

Leastsignificantbytehashighestaddress decreasesignificancewithincreasingaddress

LittleEndian(arithmeticlanguage,x86) Leastsignificantbytehaslowestaddress increasesignificancewithincreasingaddress

Example Variablex has4byterepresentation0x01234567 Addressgivenby&x is0x100

0x100 0x101 0x102 0x10301 23 45 67

0x100 0x101 0x102 0x10367 45 23 01

Big Endian

Little Endian

01 23 45 67

67 45 23 01

Reading Byte-Reversed Listings Disassembly

Textrepresentationofbinarymachinecode Generatedbyprogramthatreadsthemachinecode

ExampleFragmentAddress Instruction Code Assembly Rendition8048365: 5b pop %ebx8048366: 81 c3 ab 12 00 00 add $0x12ab,%ebx804836c: 83 bb 28 00 00 00 00 cmpl $0x0,0x28(%ebx)

DecipheringNumbers Value: 0x12ab Padto4bytes: 0x000012ab Splitintobytes: 00 00 12 ab Reverse: ab 12 00 00

Examining Data Representations CodetoPrintByteRepresentationofData

Castingpointertounsignedchar*createsbytearray

typedef unsigned char* pointer;void show_bytes(pointer start, int len){int i;for (i = 0; i < len; i++)printf("0x%p\t0x%.2x\n",

start+i, start[i]);printf("\n");

}

Printf directives:%p: Print pointer%x: Print Hexadecimal

show_bytes Execution Example

int a = 15213;printf("int a = 15213;\n");show_bytes((pointer) &a, sizeof(int));

Result (Linux):int a = 15213;0x11ffffcb8 0x6d0x11ffffcb9 0x3b0x11ffffcba 0x000x11ffffcbb 0x00

Representing Integers int A = 15213; int B = -15213; long int C = 15213;

Decimal: 15213Binary: 0011 1011 0110 1101Hex: 3 B 6 D

6D3B0000

Linux/x86-64 A

3B6D

0000

Sun A

93C4FFFF

Linux/x86-64 B

C493

FFFF

Sun B

Twos complement representation(Covered next lecture)

00000000

6D3B0000

x86-64 C

3B6D

0000

Sun C6D3B0000

Linux C

Representing Pointers int B = -15213; int *P = &B;

01000000

A0FCFFFF

x86-64 P

Different compilers & machines assign different locations to objects

FB2C

EFFF

Sun P

FFBF

D4F8

IA32 P

Representing Floats Float F = 15213.0;

IEEE Single Precision Floating Point RepresentationHex: 4 6 6 D B 4 0 0 Binary: 0100 0110 0110 1101 1011 0100 0000 000015213: 1110 1101 1011 01

Not same as integer representation, but consistent across machines

00B46D46

IA32/x86-64 F

B400

466D

Sun F

Can see some relation to integer representation, but not obvious



char S[6] = "15213";

Representing Strings StringsinC

Representedbyarrayofcharacters EachcharacterencodedinASCIIformat

Standard7bitencodingofcharacterset Otherencodingsexist,butuncommon Character0hascode0x30

Digitihascode0x30+i

Stringshouldbenullterminated Finalcharacter=0

Compatibility Byteorderingnotanissue

Dataaresinglebytequantities

Textfilesgenerallyplatformindependent Exceptfordifferentconventionsoflineterminationcharacter(s)!

IA32/x86-64 S Sun S

3231

3135

3300

3231

3135

3300

Machine-Level Code Representation EncodeProgramasSequenceofInstructions

Eachsimpleoperation Arithmeticoperation Readorwritememory Conditionalbranch

Instructionsencodedasbytes Alphas,Suns,Macsuse4byteinstructions

ReducedInstructionSetComputer(RISC) PCsusevariablelengthinstructions

ComplexInstructionSetComputer(CISC)

Differentinstructiontypesandencodingsfordifferentmachines Mostcodenotbinarycompatible

ProgramsareByteSequencesToo!

Representing Instructionsint sum(int x, int y){

return x+y;}

Different machines use totally different instructions and encodings

00003042

Alpha sum

0180FA6B

E008

81C3

Sun sum

90020009

Forthisexample,Alpha&Sunusetwo4byteinstructions Usedifferingnumbersofinstructionsinothercases

PCuses7instructionswithlengths1,2,and3bytes

E58B

5589

PC sum

450C03450889EC5DC3

Boolean Algebra DevelopedbyGeorgeBoolein19thCentury

Algebraicrepresentationoflogic EncodeTrueas1andFalseas0

And A&B=1whenbothA=1andB=1

& 0 10 0 01 0 1

~0 11 0

Not ~A=1whenA=0

Or A|B=1wheneitherA=1orB=1

| 0 10 0 11 1 1

^ 0 10 0 11 1 0

ExclusiveOr(Xor) A^B=1wheneitherA=1orB=1,

butnotboth

General Boolean Algebras OperateonBitVectors

Operationsappliedbitwise01101001

& 0101010101000001

01101001| 01010101

0111110101101001

^ 0101010100111100

~ 010101011010101001000001 01111101 00111100 10101010

Bit-Level Operations in C Operations&,|,~,^AvailableinC

Applytoanyintegraldatatype long,int,short,char,unsigned

Viewargumentsasbitvectors Argumentsappliedbitwise

Examples(Chardatatype) ~0x41>0xBE

~010000012 > 101111102 ~0x00>0xFF

~000000002 > 111111112 0x69&0x55>0x41

011010012 &010101012 >010000012 0x69|0x55>0x7D

011010012 |010101012 >011111012

Contrast: Logic Operations in C ContrasttoLogicalOperators

&&,||,! View0asFalse AnythingnonzeroasTrue Alwaysreturn0or1 Earlytermination

Examples(chardatatype) !0x41>0x00 !0x00>0x01 !!0x41>0x01

0x69&&0x55>0x01 0x69||0x55>0x01 p&&*p (avoidsnullpointeraccess)

Shift Operations LeftShift: xy Shiftbitvectorxrightypositions

Throwawayextrabitsonright

Logicalshift Fillwith0sonleft

Arithmeticshift Replicatemostsignificantbitonright Usefulwithtwoscomplementintegerrepresentation

UndefinedBehavior Shiftamount 200011000Arith. >> 2

10100010Argument x00010000> 211101000Arith. >> 2

000100000001000000011000000110000001100000011000

000100000010100011101000

000100000010100011101000

Cool Stuff with Xor

void funny(int *x, int *y){

*x = *x ^ *y; /* #1 */*y = *x ^ *y; /* #2 */*x = *x ^ *y; /* #3 */

}

BitwiseXorisformofaddition

WithextrapropertythateveryvalueisitsownadditiveinverseA^A=0

BABeginBA^B1

(A^B)^B = AA^B2A(A^B)^A = B3ABEnd

*y*x

Representing & Manipulating Sets Representation

Widthwbitvectorrepresentssubsetsof{0,,w1} aj =1ifj A

01101001 {0,3,5,6}76543210

01010101 {0,2,4,6}76543210

Operations & Intersection 01000001 {0,6} | Union 01111101 {0,2,3,4,5,6} ^ Symmetricdifference 00111100 {2,3,4,5} ~ Complement 10101010 {1,3,5,7}

replaceByte/**replaceByte(x,n,c) Replacebyteninxwithc*Bytesnumberedfrom0(LSB)to3(MSB)*Examples:replaceByte(0x12345678,1,0xab)=0x1234ab78*Youcanassume0

Boolean Algebra Integer Ring Commutativity

A|B=B|A A+B=B+AA&B=B&A A*B=B*A

Associativity(A|B)|C=A|(B|C) (A+B)+C=A+(B+C)(A&B)&C=A&(B&C) (A*B)*C=A*(B*C)

ProductdistributesoversumA&(B|C)=(A&B)|(A&C) A*(B+C)=A*B+B*C

SumandproductidentitiesA|0=A A+0=AA&1=A A*1=A

ZeroisproductannihilatorA&0=0 A*0=0

Cancellationofnegation~(~A)=A ( A)=A

Relations Between Operations DeMorgansLaws

Express&intermsof|,andviceversa A&B=~(~A|~B)

AandBaretrueifandonlyifneitherAnorBisfalse

A|B=~(~A&~B) AorBaretrueifandonlyifAandBarenotbothfalse

ExclusiveOrusingInclusiveOr A^B=(~A&B)|(A&~B)

ExactlyoneofAandBistrue

A^B=(A|B)&~(A&B) EitherAistrue,orBistrue,butnotboth

Main Points ItsAllAboutBits&Bytes

Numbers Programs Text

DifferentMachinesFollowDifferentConventions Wordsize Byteordering Representations

BooleanAlgebraisMathematicalBasis Basicformencodesfalseas0,trueas1 GeneralformlikebitleveloperationsinC

Goodforrepresenting&manipulatingsets

Computer Organization 33

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