8/4/2019 Computer Science 37 Lecture 1
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1.1
Where:MooreB03
When:MWF11:15-12:25
X-Hour:Tuesday12:00
LuizFelipe Perrone,Sudikoff 209
Cybersecurity ResearchGroup
ISTSDartmouthCollege
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1.2
Administrivia
1) Wehaveawebpage:
http://www.cs.dartmouth.edu/~cs37
(syllabus,slides,readings,andalladministrivia)
2) TAs:ClintHepner andMingLi
3) OfficeHours
4) Textbook:onerequiredplusanothertwofor
whoreally wantsmore.
5) X-Hours:Ijustcantgetenough.
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1.3
Administrivia
6) HonorPrinciple:readit,abidebyit.
7) Grades:
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=
7
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ihwHW
05.1*
025.1*
g
g
g Nopaper,badpaper
Bpaper
Apaper
g=QZ+MT+FE+HW
QZ=6%,MT=20%,FE=24%,HW=49%
=
=
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Finalgrade:
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1.4
Lecture1
AbstractionLayers
WhereBitsAreBorn
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1.5
LayersofAbstraction
abstraction:
theactorprocessofabstracting.
abstracting:
tomakeanabstractof,tosummarize.
Thinkabouthowyouinteractwiththeworld:
Youdontconstantlythinkaboutallthedetailsineverything aroundyou.Youthinkaboutessentials.
Youdealwithfunctionblocks andinterfaces.
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1.6
LayersofAbstraction
Pointstoconsider:
1) Givesomethinganinputandgetsomethingfrom
itasoutput.Itsthefunctionality thatmatters.
2) Whenwecanconceptuallybreakdownasystem
intocooperatingcomponents,theinterface
betweencomponentsmustbewellunderstood.
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1.7
LayersofAbstraction
functiondomain range
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1.8
LayersofAbstraction
f()
program
inputdata
outputdata
computer
domain
range
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1.9
Interlude:AlanTuring,FounderofComputerScience
1912(23June):Birth,Paddington,London
1931-34:UndergraduateatKing'sCollege,CambridgeUniversity
1932-35:Studiesquantummechanics,probability,logic1936:TheTuringmachine:OnComputableNumbers... submitted
1936-38:AtPrincetonUniversity.Ph.D.Papersinlogic,algebra,numbertheory
1938-39:ReturntoCambridge.IntroducedtoGermanEnigmacipherproblem
1939-40DevisestheBombe,machineforEnigmadecryption
1939-42:BreakingofU-boatEnigmacipher,savingbattleoftheAtlantic
1943-45:ChiefAnglo-Americanconsultant.Introducedtoelectronics
1946:Computerdesign,leadingtheworld,formallyaccepted
1947-48:Papersonprogramming,neuralnets,andprospectsforartificial
intelligence
1949:Workonprogrammingandworld'sfirstserioususeofacomputer
1950:Philosophicalpaperonmachineintelligence:theTuringTest
1952:Arrestedandtriedasahomosexual,lossofsecurityclearance
1954(7June):Deathbycyanidepoisoning,Wilmslow,Cheshire.
Turing
Machine
data
program
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1.10
LayersofAbstraction
Application
SystemSoftware
Hardware
Compilers,webbrowsers,word
processors,MP3players,etc.
Abstractions:
servetohidedetailbehindfunctionality,
youconcentrateonwhatyoumust,
allowforagoodmeasureofflexibility.
I/Odevicecontrol,processscheduling,
virtualmemory,filesystem,etc.
Arithmeticoperations,datatransfer,
memory,massstorage,etc.
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1.11
LayersofAbstraction
Application
SystemSoftware
Hardware
FunctionalComponentsBus,CPU,Memory
LogicGates
DiscreteElectronicComponents
AND,OR,NOT,
transistor,
capacitor,
resistor,
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1.12
Whystoopthatlow?
Understand howoneimplementsahigh-levellanguage(compilerconstruction).
Understand howanoperatingsystemisconstructed.
Understand howonedesignsalowlevellanguage:theprocessorsinstructionset.
Understand whatyou[can]getfromaprocessor(performance).
Understand howtobettercontrolthecomputerso
youcangetthemaximumitcangiveyou.Understand yoursystemchoices.
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1.13
Switch:TheBasicBuildingBlock
0V
Whentheswitchis
closed,currentcanflow
fromthesourcetothe
ground.
hasthesamepotential
astheground.
Whentheswitchis
open,currentcannot
flow.
0V hasthesamepotentialasthe
source.
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1.14
InformationRepresentation
Theswitch hastwopossiblestates:
BINARYSYSTEM
Question: Isthissystemtoorestrictive?
surely1
surely0
uncertainty
zone
0
potential(V)
+5
V
V
0
1
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1.15
Whatyoucandowithswitches
(1)
(2)
(3)
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1.16
Whatyoucantdowithswitches
Youcantcontrolthemelectronically.
Youdontwanttohavetomechanically
setAandB(pushthemwithyour
fingers)whenyouwanttocomputea
function.
Whatyoudowantistobeabletoset
theirvalueswithanelectricsignal
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1.17
MechanicalLimitation
input output
0V
time
Canreadtheoutput
valuefromthispointon
Duringthistime
theoutputvalueismeaningless
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1.18
Switch:TheBasicBuildingBlock
0V
Whencurrentininjected
fromthebase,current
canflowfromthe
collectortotheemitter.
willhavethesame
potentialasground.
base
collector
emitter
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1.19
TheNotFunctionwithaTransistor
oV iV
0V+5V
+5V0V
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1.20
TheNotFunctionwithaLogicGate
01
10
BA
Truthtable
input
variable
output
variable
Fromdiscretecomponentsto
logicgates:ourfirstmoveuptowardahigherlayerof
abstraction.
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1.21
Interlude:AnotherLowerLayer?
FunctionalComponents
LogicGates
DiscreteElectronicComponents
bitstrings
bits
electriccurrents
DiscreteSpintronic Components electronsspins
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1.22
PuttingInformationin
ElectronsStatesUseelectronspin(angular
momentum)torepresentbinary
values:{down,up}={0,1}
5bits
All possiblevaluesatonce:
5
2
+ =
Aqubitdiffersfromabitinthat
itcanassumeasuperpositionof
states:theycanbeboth0and1simultaneously.
00110
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AdvantagesofSpintronics
Spindoesntchangewhendevicesarepoweredoff:wecanhavenicermemoriesbuiltwiththistechnology.
Consumelesspower.
Incrediblyfastercomputation.
Moreintegration.
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TheChallengeinSpintronics
Whenaqubitinteractswiththe
surrounding,itsvalueis
convertedtoarandombit.
Toreadthevalueofaqubit,
youneedtointeractwithit
?
Whilequantumcomputingis
afar-offgoal,spintronics may
allowforvastimprovements
whencombinedwithconventionalsemiconductor
technology.