Introduction to Programming Languageopen.gnu.ac.kr/lecslides/2017-2-introProg/IPL-python-01.pdf · 2017-08-28 · Introduction to Programming Language 7. About this Course •Academic

IntroductiontoProgrammingLanguage

Lecture1

*Somematerialsadaptedfromocw.mit.edu 6.0001

Today’sAgenda• CourseLayout

• Whatiscomputation

• Python

IntroductiontoProgrammingLanguage 2

CourseLayout


AboutthisCourse• Instructor• SeongjinLee

• Email:[email protected]

• Office:407-314

• OfficeHour:EveryThursday11:00-12:00orMakeappointment

• Class• Time:Thursday16:00-19:00

• Place:407-202

• Coursewebpage• http://open.gnu.ac.kr컴퓨터프로그래밍기초


AboutthisCourse• Python• 모두의파이썬 20일만에배우는프로그래밍기초 |이승찬지음 |길벗

• AllenB.Downey,"ThinkPython:HowtoThinkLikeaComputerScientist",2015

• C• K.N.King,"CProgramming:AModernApproach,"W.W.Norton&Company,2ndEdition,2008

• BrianW.Kernighan,DennisM.Ritchie,"CProgrammingLanguage"PrenticeHall,1988(2ndEdition)(Kernighan의 C언어프로그래밍)

• StephenPrata."CPrimerPlus".Sams,2004(C기초플러스)

• 어서와 C언어는처음이지!초보자를위한 C프로그래밍완벽가이드 |그레그페

리 ,딘밀러지음 |천인국옮김 |인피니티북스


AboutthisCourse• Goal– Concepts,programmingskills,problemsolving

• Evaluation• Attendance– 10%

• Assignments– 20%

• Exam1– 25%

• Exam2- 25%

• Exam3- 30%

• Closedbookandnotes

• Requestforregradewithinoneweekuponreturn;describereasonsinwriting

• whatandwhythescoreisincorrectorunfair

• Thewrittenargumentmustbeself-contained


AboutthisCourse• ReadingAssignments– Duebeforefollowingclassperiod

• Attendance• Participationisimportantpartofthiscourse

• 3absenceswithoutpriorarrangementwillloweryourgradebyoneletter(eachsubsequent1absenceswillloweragradebyoneletter)

• FixedSittings• Ifyouhavetroublehearingmeorseeingthescreen,nowisthetimetochangeyoursits

• Eachstudentswillbeassignedanumber,usethatnumberoneverypieceofworkyouhandin


AboutthisCourse• AcademicHonesty• Assignments,quizzes,andexamsdoneindividually

• Nolying,cheating,copying

• Iffound,nogradeforthatparticularassessment

• Suspiciousworkwillbequestionedthoroughly


AboutthisCourse• Noclasseson추석

• Exams• Closebookandnotes

• Exam1onOct.10th (inclass)– 407-101

• Exam2onNov.11th (inclass)– 407-101

• Exam3onDec.12th (inclass)– 407-101

• Survey• Togivefeedbackonyourunderstandingofmaterialaswellashelpwithmaterial


Assignmentsforeveryweek• Chooseanythreeconcepts• Writetheconceptonthetopofthepage

• Explaintheconceptwithyourwords(makesureanybodycanunderstandtheconcept)

• Giveanexampleoftheconcept

• 1pageforeachconcept

• YouaretohanditoneveryTuesdaymorning

• Nohandwrittenpapers


Howtosucceedinthiscourse• Readcodeandthemanual

• Makemistakesandlearnwhy

• Keepitsimple


Don’t practice until you get it right

Practice until you can’t get it wrong

Whatiscomputation


WhatDoesAComputerDo• Fundamentally:• performscalculations

• abillioncalculationspersecond!

• remembersresults

• 100sofgigabytesofstorage!

• Whatkindsofcalculations?• built-intothelanguage

• onesthatyoudefineastheprogrammer

• Computersonlyknowwhatyoutellthem


TypesOfKnowledge• declarativeknowledgeisstatementsoffact.

• imperativeknowledgeisarecipeor“how-to”.


AnumericalExample• squarerootofanumberx isysuchthaty*y=x

• recipefordeducingsquarerootofanumberx(16)1. Startwithaguess,g

2. Ifg*giscloseenoughtox,stopandsaygistheanswer

3. Otherwisemakeanewguessbyaveraginggandx/g

4. Usingthenewguess,repeatprocessuntilcloseenough


g g*g x/g (g+x/g)/2

3 9 16/3 4.17

4.17 17.36 3.837 4.0035

4.0035 16.0277 3.997 4.000002

Whatisarecipe1. Sequenceofsimplesteps

2. flowofcontrolprocessthatspecifieswheneachstepisexecuted

3. ameansofdeterminingwhentostop

1+2+3=analgorithm!


Computersaremachines• Howtocapturearecipeinamechanicalprocess

1. fixedprogramcomputer:Calculator

2. StoredProgramcomputer:machinestoresandexecutesinstructions


BasicMachineArchitecture


MEMORY

ControlUnit ArithmeticLogicUnit

INPUT OUTPUT

programcounter primitiveoperations

StoredProgramComputer• Sequenceofinstructionsstoredinsidecomputer• builtfrompredefinedsetofprimitiveinstructions

1. arithmeticandlogic

2. simpletests

3. movingdata

• specialprogram(interpreter)executeseachinstructioninorder• useteststochangeflowofcontrolthroughsequence

• stopwhendone


BasicPrimitives• Turingshowedthatyoucancomputeanythingusing6primitives• Moveleft,Moveright,Print,Scan,Erase,Donothing

• ifyouareinterestedtolearnmoreaboutit:reference orsmallvideo

• modernprogramminglanguageshavemoreconvenientsetofprimitives

• canabstractmethodstocreatenewprimitives

• anythingcomputableinonelanguageiscomputableinanyotherprogramminglanguage


CreatingRecipes• aprogramminglanguageprovidesasetofprimitiveoperations

• expressionsarecomplexbutlegalcombinationsofprimitivesinaprogramminglanguage

• expressionsandcomputationshavevaluesandmeaningsinaprogramminglanguage


AspectsofLanguages• Primitiveconstructs:SyntaxandSemantic• Syntax:Definesthegrammar

• Semantic:isthemeaningassociatedwithsyntacticallycorrectsymbolswithnosemanticerrors

• English/Korean:Words

• 아버지가방에들어가신다 – syntacticallyvalidbutsemanticallynotcorrect

• 아기고기다리 – notsyntacticallyvalid

• ProgrammingLanguage:Numbers,Strings,Simpleoperators

• 3.14*8– syntacticallyvalid

• “hi”5– notsyntacticallyvalid


AspectsofLanguages


• Naturallanguageshavemanymeanings

• ProgrammingLanguageshaveonlyonemeaningbutmaynotbewhatprogrammerintended

Wherethingsgowrong• syntacticerrors• commonandeasilycaught

• staticsemanticerrors• somelanguagescheckforthesebeforerunningprogram

• cancauseunpredictablebehavior

• nosemanticerrorsbutdifferentmeaningthanwhatprogrammerintended• programcrashes,stopsrunning

• programrunsforever

• programgivesananswerbutdifferentthanexpected


Python


PythonPrograms• aprogramisasequenceofdefinitionsandcommands• definitionsevaluated

• commandsexecutedbyPythoninterpreterinashell

• commands(statements)instructinterpretertodosomething

• canbetypeddirectlyinashellorstoredinafilethatisreadintotheshellandevaluated


Objects• Pythonprogrammanipulatesdataobjects

• Objectshaveatypethatdefinesthekindsofthingsprogramcandotothem

• objectsare• scalar(cannotbesubdivided)

• non-scalar


Scalarobjects• int – representintegers,ex.1,2,3,4,etc.

• float– representrealnumbers,ex.3.14,48.12

• bool– representBooleanvaluesTrueandFalse

• canusetype()toseethetypeofanobject


>>>type(5)int>>>type(3.14)float

Typeconversion(cast)• canconvertobjectofonetypetoanother

• example:• float(3)convertsinteger3tofloat(3.0)

• int(3.9)truncatesfloat3.9tointeger3


Printingtoconsole• toshowoutputfromcodetoauser,useprintcommand


In[30]:3+8Out[30]:11

In[31]:print(3+8)11

“out”tellsyouit’saninteractionwithintheshellonly

No“out”meansitisactuallyshowntoauserwhenyourunafile

Expressions• combinesobjectsandoperatorstoformexpressions

• anexpressionhasavalue,whichhasatype

• syntaxforasimpleexpression• <object><operator><object>


Operatorsforint andfloattypes• i+jà sum,int->int,float->float

• i-jà difference ,int->int,float->float

• i*jà product ,int->int,float->float

• i/jà division,resultisalwaysfloat

• i%jà themodularoperator,itgivesremainderwhenIisdividedbyj

• i **jà Itothepowerofj


Bindingvariablesandvalues• equalsignisanassignmentofavaluetoavariablename

• valuestoredincomputermemory

• anassignmentbindsnametovalue

• retrievevalueassociatedwithnameorvariablebyinvokingthename,bytypingpi


pi=3.141592pi_approx =22/7

Abstractingexpressions• Whygivenamestovaluesofexpressions?• toreusenamesinsteadofvalues

• easiertochangethecodelater


pi=3.141592radious =2.2area=pi*(radious**2)

ToDo


Whenyougobackhome• Makesureyoureadthetextandunderstandthemeaning

• Chooseanythreeconceptsandwriteareportoneachconcepts

• InstallLinuxusingaVirtualmachineornatively.• installfollowingprograms

• sudo apt-getinstallpythonviemacs spyder


Introduction to Programming Languageopen.gnu.ac.kr/lecslides/2017-2-introProg/IPL-python-01.pdf · 2017-08-28 · Introduction to Programming Language 7. About this Course •Academic

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