computer science 37 lecture 1

8/4/2019 Computer Science 37 Lecture 1

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1

1.1

Where:MooreB03

When:MWF11:15-12:25

X-Hour:Tuesday12:00

LuizFelipe Perrone,Sudikoff 209

Cybersecurity ResearchGroup

ISTSDartmouthCollege


2/24

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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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3

1.3

Administrivia

6) HonorPrinciple:readit,abidebyit.

7) Grades:

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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.


6/24

6

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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10

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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13

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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1.23

AdvantagesofSpintronics

Spindoesntchangewhendevicesarepoweredoff:wecanhavenicermemoriesbuiltwiththistechnology.

Consumelesspower.

Incrediblyfastercomputation.

Moreintegration.


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1.24

TheChallengeinSpintronics

Whenaqubitinteractswiththe

surrounding,itsvalueis

convertedtoarandombit.

Toreadthevalueofaqubit,

youneedtointeractwithit

?

Whilequantumcomputingis

afar-offgoal,spintronics may

allowforvastimprovements

whencombinedwithconventionalsemiconductor

technology.

computer science 37 lecture 1

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