22 ideals

Software ideals and historySoftware ideals and history
Bjarne StroustrupBjarne Stroustrup
www.stroustrup.com/Programmingwww.stroustrup.com/Programming
Arun Prakash MArun Prakash M - GUVI- GUVI
( Tamil Narration)( Tamil Narration)

AcknowledgmentAcknowledgment
Stroustrup/ProgrammingStroustrup/Programming 22

OverviewOverview
 IdealsIdeals
 Aims, heroes, techniquesAims, heroes, techniques
 Languages and language designersLanguages and language designers
 Early languages to C++Early languages to C++
(There is so much more than(There is so much more than
what we can cover)what we can cover)
44Stroustrup/ProgrammingStroustrup/Programming

History and ideasHistory and ideas
 One opinionOne opinion
 History is bunkHistory is bunk
 Another opinionAnother opinion
 He who does not know history is condemned to repeat itHe who does not know history is condemned to repeat it
 Our viewOur view
 There can beThere can be no professionalism without historyno professionalism without history
 If you know too little of the background of your field you areIf you know too little of the background of your field you are
gulliblegullible
 History is littered with plausible ideas that didn’t workHistory is littered with plausible ideas that didn’t work
 ““I have a bridge I’d like to sell you”I have a bridge I’d like to sell you”
 Ideas and ideals are crucial for practical useIdeas and ideals are crucial for practical use
 And they are the real “meat” of historyAnd they are the real “meat” of history

What is a programming language?What is a programming language?
 A tool for instructing machinesA tool for instructing machines
 A notation for algorithmsA notation for algorithms
 A means for communication among programmersA means for communication among programmers
 A tool for experimentationA tool for experimentation
 A means for controlling computer-controlled gadgetsA means for controlling computer-controlled gadgets
 A means for controlling computerized devicesA means for controlling computerized devices
 A way of expressing relationships among conceptsA way of expressing relationships among concepts
 A means for expressing high-level designsA means for expressing high-level designs
 All of the above!All of the above!
 And moreAnd more

Greek heroesGreek heroes
 Every culture and profession must have ideals and heroesEvery culture and profession must have ideals and heroes
 Physics: Newton, Einstein, Bohr, FeynmanPhysics: Newton, Einstein, Bohr, Feynman
 Math: Euclid, Euler, HilbertMath: Euclid, Euler, Hilbert
 Medicine: Hippocrates, Pasteur, FlemingMedicine: Hippocrates, Pasteur, Fleming

Geek heroesGeek heroes
 Brian KernighanBrian Kernighan
 Programmer and writerProgrammer and writer
extraordinaireextraordinaire
88
 Dennis RitchieDennis Ritchie
 Designer and originalDesigner and original
implementer of Cimplementer of C
Stroustrup/ProgrammingStroustrup/Programming

Another geek heroAnother geek hero
 Kristen NygaardKristen Nygaard
 Co-inventor (with Ole-Co-inventor (with Ole-
Johan Dahl) of Simula67Johan Dahl) of Simula67
and of object-orientedand of object-oriented
Programming andProgramming and
object-oriented designobject-oriented design

Yet another geek heroYet another geek hero
 Alex StepanovAlex Stepanov
 Inventor of the STL andInventor of the STL and
generic programminggeneric programming
pioneerpioneer

Two extremesTwo extremes
 Academic beauty/perfection/purityAcademic beauty/perfection/purity
 Commercial expediencyCommercial expediency
 The pressures towards both are immenseThe pressures towards both are immense
 Both extremes must be avoided for serious progress to occurBoth extremes must be avoided for serious progress to occur
 Both extremes encourage overstatement of results (hype) andBoth extremes encourage overstatement of results (hype) and
understatement (or worse) of alternatives and ancestor languagesunderstatement (or worse) of alternatives and ancestor languages

IdealsIdeals
 The fundamental aims of good designThe fundamental aims of good design
 Represent ideas directly in codeRepresent ideas directly in code
 Represent independent ideas independently in codeRepresent independent ideas independently in code
 Represent relationships among ideas directly in codeRepresent relationships among ideas directly in code
 Combine ideas expressed in code freelyCombine ideas expressed in code freely
 where and only where combinations make sensewhere and only where combinations make sense
 From these followFrom these follow
 CorrectnessCorrectness
 MaintainabilityMaintainability
 PerformancePerformance
 Apply these to the widest possible range ofApply these to the widest possible range of
applicationsapplications

Ideals have practical usesIdeals have practical uses
 During the start of a project, reviews them to get ideasDuring the start of a project, reviews them to get ideas
 When you are stuck late at night, step back and seeWhen you are stuck late at night, step back and see
where your code has most departed from the ideals –where your code has most departed from the ideals –
this is where the bugs are most likely to lurk and thethis is where the bugs are most likely to lurk and the
design problems are most likely to occurdesign problems are most likely to occur
 Don’t just keep looking in the same place and trying theDon’t just keep looking in the same place and trying the
same techniques to find the bugsame techniques to find the bug
 ““The bug is always where you areThe bug is always where you are notnot looking – or you would havelooking – or you would have
found it already”found it already”

Ideals are personalIdeals are personal
 Chose yours wellChose yours well

Styles/paradigmsStyles/paradigms
 Procedural programmingProcedural programming
 Data abstractionData abstraction
 Object-oriented programmingObject-oriented programming
 Generic programmingGeneric programming
 Functional programming, Logic programming, rule-Functional programming, Logic programming, rule-
based programming, constraints-based programming,based programming, constraints-based programming,
aspect-oriented programming, …aspect-oriented programming, …

Styles/paradigmsStyles/paradigms
template<class Iter> void draw_all(Iter b, Iter e)template<class Iter> void draw_all(Iter b, Iter e)
{{
for_each(b,e,mem_fun(&Shape::draw)); //for_each(b,e,mem_fun(&Shape::draw)); // draw all shapes in [b:e)draw all shapes in [b:e)
}}
Point p(100,100);Point p(100,100);
Shape* a[] = { new Circle(p,50), new Rectangle(p, 250, 250) };Shape* a[] = { new Circle(p,50), new Rectangle(p, 250, 250) };
draw_all(a,a+2);draw_all(a,a+2);
 Which programming styles/paradigms did we use here?Which programming styles/paradigms did we use here?
 Procedural, data abstractions, OOP, and GPProcedural, data abstractions, OOP, and GP

Some fundamentalsSome fundamentals
 Portability is goodPortability is good
 Type safety is goodType safety is good
 High performance is goodHigh performance is good
 Anything that eases debugging is goodAnything that eases debugging is good
 Access to system resources is goodAccess to system resources is good
 Stability over decades is goodStability over decades is good
 Ease of learning is goodEase of learning is good
 Small is goodSmall is good
 Whatever helps analysis is goodWhatever helps analysis is good
 Having lots of facilities is goodHaving lots of facilities is good
 You can’t have all at the same time: engineering tradeoffsYou can’t have all at the same time: engineering tradeoffs

Programming languagesProgramming languages
 Machine codeMachine code
 Bits, octal, or at most decimal numbersBits, octal, or at most decimal numbers
 AssemblerAssembler
 Registers, load, store, integer add, floating point add, …Registers, load, store, integer add, floating point add, …
 Each new machine had its own assemblerEach new machine had its own assembler
 Higher level languagesHigher level languages
 First: Fortran and COBOLFirst: Fortran and COBOL
 Rate of language inventionRate of language invention
 At least 2000 a decadeAt least 2000 a decade
 Major languages todayMajor languages today
 Really solid statistics are hard to come byReally solid statistics are hard to come by
 IDS: about 9 million professional programmersIDS: about 9 million professional programmers
 COBOL, Fortran, C, C++, Visual Basic, PERL, Java, JavascriptCOBOL, Fortran, C, C++, Visual Basic, PERL, Java, Javascript
 Ada, C#, PHP, …Ada, C#, PHP, …

Early programming languagesEarly programming languages
1919
Classic C
Simula
Pascal
Algol68
BCPL
Fortran
Lisp
COBOL
Algol60
PL1
1950s: 1960s: 1970s:
Red==major commercial use
Yellow==will produce important “offspring”

Modern programming languagesModern programming languages
2020
Object Pascal
C++
Java95
C#Ada98
C++98
Java04
C++0x
PythonLisp
Smalltalk
Fortran77
Ada
Eiffel
Simula67
COBOL89
PHP
C89
Pascal
PERL
Visual Basic
COBOL04 Javascript

Why do we design and evolve languages?Why do we design and evolve languages?
 There are many diverse applications areasThere are many diverse applications areas
 No one language can be the best for everythingNo one language can be the best for everything
 Programmers have diverse backgrounds and skillsProgrammers have diverse backgrounds and skills
 No one language can be best for everybodyNo one language can be best for everybody
 Problems changeProblems change
 Over the years, computers are applied in new areas and to new problemsOver the years, computers are applied in new areas and to new problems
 Computers changeComputers change
 Over the decades, hardware characteristics and tradeoffs changeOver the decades, hardware characteristics and tradeoffs change
 Progress happensProgress happens
 Over the decades, we learn better ways to design and implementOver the decades, we learn better ways to design and implement
languageslanguages

First modern computer – first compilerFirst modern computer – first compiler
 David WheelerDavid Wheeler
 University of CambridgeUniversity of Cambridge
 Exceptional problem solver: hardware, software, algorithms, librariesExceptional problem solver: hardware, software, algorithms, libraries
 First computer science Ph.D. (1951)First computer science Ph.D. (1951)
 First paper on how to write correct, reusable, and maintainable code (1951)First paper on how to write correct, reusable, and maintainable code (1951)
 (Thesis advisor for Bjarne Stroustrup(Thesis advisor for Bjarne Stroustrup ))

Early languages – 1952Early languages – 1952
 One language for each machineOne language for each machine
 Special features for processorSpecial features for processor
 Special features for “operating system”Special features for “operating system”
 Most had very assembler-like facilitiesMost had very assembler-like facilities
 It was easy to understand which instructions would be generatedIt was easy to understand which instructions would be generated
 No portability of codeNo portability of code

FortranFortran
 John BackusJohn Backus
 IBMIBM
 FORTRAN, the first high level computer language to be developed.FORTRAN, the first high level computer language to be developed.
 We did not know what we wanted and how to do it. It just sort of grew.We did not know what we wanted and how to do it. It just sort of grew.
 The Backus-Naur Form (BNF), a standard notation to describe theThe Backus-Naur Form (BNF), a standard notation to describe the
syntax of a high level programming language.syntax of a high level programming language.
 A functional programming language called FP, which advocates aA functional programming language called FP, which advocates a
mathematical approach to programmingmathematical approach to programming..

Fortran – 1956Fortran – 1956
 Allowed programmers to write linear algebra much as theyAllowed programmers to write linear algebra much as they
found it in textbooksfound it in textbooks
 Arrays and loopsArrays and loops
 Standard mathematical functionsStandard mathematical functions
 librarieslibraries
 Users’ own functionsUsers’ own functions
 The notation was largely machine independentThe notation was largely machine independent
 Fortran code could often be moved from computer to computer withFortran code could often be moved from computer to computer with
only minor modificationonly minor modification
 This was aThis was a hugehuge improvementimprovement
 Arguably the largest single improvement in the history of programmingArguably the largest single improvement in the history of programming
languageslanguages
 Continuous evolution: II, IV, 77, 90, 0xContinuous evolution: II, IV, 77, 90, 0x

COBOLCOBOL
 ““Rear Admiral Dr. Grace Murray Hopper (USRear Admiral Dr. Grace Murray Hopper (US
Navy) was a remarkable woman who grandlyNavy) was a remarkable woman who grandly
rose to the challenges of programming the firstrose to the challenges of programming the first
computers. During her lifetime as a leader incomputers. During her lifetime as a leader in
the field of software development concepts, shethe field of software development concepts, she
contributed to the transition from primitivecontributed to the transition from primitive
programming techniques to the use ofprogramming techniques to the use of
sophisticated compilers. She believed thatsophisticated compilers. She believed that
‘we've always done it that way’ was not‘we've always done it that way’ was not
necessarily a good reason to continue to do so.”necessarily a good reason to continue to do so.”

Cobol – 1960Cobol – 1960
 Cobol was (and sometimes still is) for business programmersCobol was (and sometimes still is) for business programmers
what Fortran was (and sometimes still is) for scientificwhat Fortran was (and sometimes still is) for scientific
programmersprogrammers
 The emphasis was on data manipulationThe emphasis was on data manipulation
 CopyingCopying
 Storing and retrieving (record keeping)Storing and retrieving (record keeping)
 Printing (reports)Printing (reports)
 Calculation/computation was seen as a minor matterCalculation/computation was seen as a minor matter
 It was hoped/claimed that Cobol was so close to businessIt was hoped/claimed that Cobol was so close to business
English that managers could program and programmers wouldEnglish that managers could program and programmers would
soon become redundantsoon become redundant
 Continuous evolution: 60, 61, 65, 68, 70, 80, 90, 04Continuous evolution: 60, 61, 65, 68, 70, 80, 90, 04

LispLisp
 John McCarthyJohn McCarthy
 Stanford UniversityStanford University
 AI pioneerAI pioneer

Lisp – 1960Lisp – 1960
 List/symbolic processingList/symbolic processing
 Initially (and often still) interpretedInitially (and often still) interpreted
 Dozens (most likely hundreds) of dialectsDozens (most likely hundreds) of dialects
 ““Lisp has an implied plural”Lisp has an implied plural”
 Common LispCommon Lisp
 SchemeScheme
 This family of languages has been (and is) theThis family of languages has been (and is) the
mainstay of artificial intelligence (AI) researchmainstay of artificial intelligence (AI) research
 though delivered products have often been in C or C++though delivered products have often been in C or C++

AlgolAlgol
 Peter NaurPeter Naur
 Danish Technical University and RegnecentralenDanish Technical University and Regnecentralen
 BNFBNF
 Edsger DijkstraEdsger Dijkstra
 Mathematisch Centrum, Amsterdam, Eindhoven University ofMathematisch Centrum, Amsterdam, Eindhoven University of
Technology, Burroughs Corporation , University of Texas (Austin)Technology, Burroughs Corporation , University of Texas (Austin)
 Mathematical logic in programming, algorithmsMathematical logic in programming, algorithms
 THE operating systemTHE operating system

Algol – 1960Algol – 1960
 The breakthrough of modern programming language conceptsThe breakthrough of modern programming language concepts
 Language descriptionLanguage description
 BNF; separation of lexical, syntactic, and semantic concernsBNF; separation of lexical, syntactic, and semantic concerns
 ScopeScope
 TypeType
 The notion of “general purpose programming language”The notion of “general purpose programming language”
 Before that languages were either scientific (e.g., Fortran), business (e.g.,Before that languages were either scientific (e.g., Fortran), business (e.g.,
Cobol), string manipulation (e.g., Lisp), simulation, …Cobol), string manipulation (e.g., Lisp), simulation, …
 Never reached major non-academic useNever reached major non-academic use
3131
Algol58 Algol60
Simula67
Algol68
PascalStroustrup/ProgrammingStroustrup/Programming

Simula 67Simula 67
 Kristen Nygaard and Ole-Johan DahlKristen Nygaard and Ole-Johan Dahl
 Norwegian Computing CenterNorwegian Computing Center
 Oslo UniversityOslo University
 The start of object-oriented programming and object-oriented designThe start of object-oriented programming and object-oriented design

Simula 1967Simula 1967
 Address all applications domains rather then a specific domainAddress all applications domains rather then a specific domain
 As Fortran, COBOL, etc. didAs Fortran, COBOL, etc. did
 Aims to become a true general-purpose programming languageAims to become a true general-purpose programming language
 Model real-world phenomena in codeModel real-world phenomena in code
 represent ideas as classes and class objectsrepresent ideas as classes and class objects
 represent hierarchical relations as class hierarchiesrepresent hierarchical relations as class hierarchies
 Classes, inheritance, virtual functions, object-oriented designClasses, inheritance, virtual functions, object-oriented design
 A program becomes a set of interacting objects rather than aA program becomes a set of interacting objects rather than a
monolithmonolith
 Has major (positive) implications for error ratesHas major (positive) implications for error rates

CC Dennis RitchieDennis Ritchie
 Bell LabsBell Labs
 C and helped with UnixC and helped with Unix
 Ken ThompsonKen Thompson
 Bell LabsBell Labs
 UnixUnix
3434
 Doug McIlroyDoug McIlroy
 Bell LabsBell Labs
 Everybody’s favorite critic,Everybody’s favorite critic,
discussion partner, anddiscussion partner, and
ideas man (influenced C,ideas man (influenced C,
C++, Unix, and muchC++, Unix, and much
more)more)

Bell Labs – Murray HillBell Labs – Murray Hill

C – 1978C – 1978
 (Relatively) high-level programming language for systems(Relatively) high-level programming language for systems
programmingprogramming
 Very widely used, relatively low-level, weakly typed, systemsVery widely used, relatively low-level, weakly typed, systems
programming languageprogramming language
 Associated with Unix and through that with Linux and the open sourceAssociated with Unix and through that with Linux and the open source
movementmovement
 Performance becomes somewhat portablePerformance becomes somewhat portable
 Designed and implemented by Dennis Ritchie 1974-78Designed and implemented by Dennis Ritchie 1974-78
3636
CPL BCPL B
C99
C++
C89
Classic C
C++98
Christopher Strachey, Cambridge, mid-
1960s
Martin Richards, Cambridge, 1967
Ken Thompson, BTL, 1972
Dennis Ritchie, BTL, 1974
C++0x
Bjarne Stroustrup, BTL, 1985

C++C++
 Bjarne StroustrupBjarne Stroustrup
 AT&T Bell labsAT&T Bell labs
 Texas A&M UniversityTexas A&M University
 making abstraction techniques affordable andmaking abstraction techniques affordable and
manageable for mainstream projectsmanageable for mainstream projects
 pioneered the use of object-oriented and genericpioneered the use of object-oriented and generic
programming techniques in application areas whereprogramming techniques in application areas where
efficiency is a premiumefficiency is a premium

My ideals –My ideals – in 1980 and still in 2008in 1980 and still in 2008
 ““To make life easier for the serious programmer”To make life easier for the serious programmer”
 i.e., primarily me and my friends/colleaguesi.e., primarily me and my friends/colleagues
 I love writing codeI love writing code
 I like reading codeI like reading code
 I hate debuggingI hate debugging
 Elegant and efficient codeElegant and efficient code
 I really dislike choosing between the twoI really dislike choosing between the two
 Elegance, efficiency, and correctness are closely relatedElegance, efficiency, and correctness are closely related
in many application domainsin many application domains
 Inelegance/verbosity is a major source of bugs and inefficienciesInelegance/verbosity is a major source of bugs and inefficiencies

C++ – 1985C++ – 1985
 C++ is a general-purpose programming languageC++ is a general-purpose programming language
with a bias towards systems programming thatwith a bias towards systems programming that
 is a better Cis a better C
 supports data abstractionsupports data abstraction
 supports object-oriented programmingsupports object-oriented programming
 supports generic programmingsupports generic programming
3939
Classic C
Simula 67
C++C with Classes
C++98
ARM C++
1979-84
1978-89
1989
C++0c

More informationMore information
 More language designer links/photosMore language designer links/photos
 http://www.angelfire.com/tx4/cus/people/http://www.angelfire.com/tx4/cus/people/
 A few examples of languages:A few examples of languages:
 http://dmoz.org/Computers/Programming/Languages/http://dmoz.org/Computers/Programming/Languages/
 TextbooksTextbooks
 Michael L. Scott,Michael L. Scott, Programming Language PragmaticsProgramming Language Pragmatics, Morgan, Morgan
Kaufmann, 2000, ISBN 1-55860-442-1Kaufmann, 2000, ISBN 1-55860-442-1
 Robert W. Sebesta,Robert W. Sebesta, Concepts of programming languagesConcepts of programming languages,,
Addison-Wesley, 2003, ISBN 0-321-19362-8Addison-Wesley, 2003, ISBN 0-321-19362-8
 History booksHistory books
 Jean Sammet,Jean Sammet, Programming Languages: History andProgramming Languages: History and
FundamentalsFundamentals, Prentice-Hall, 1969, ISBN 0-13-729988-5, Prentice-Hall, 1969, ISBN 0-13-729988-5
 Richard L. Wexelblat,Richard L. Wexelblat, History of Programming LanguagesHistory of Programming Languages,,
Academic Press, 1981, ISBN 0-12-745040-8Academic Press, 1981, ISBN 0-12-745040-8
 T. J. Bergin and R. G. Gibson,T. J. Bergin and R. G. Gibson, History of ProgrammingHistory of Programming
Languages – IILanguages – II, Addison-Wesley, 1996, ISBN 0-201-89502-1, Addison-Wesley, 1996, ISBN 0-201-89502-1

22 ideals

Empfohlen

Empfohlen

Weitere ähnliche Inhalte

Ähnlich wie 22 ideals

Ähnlich wie 22 ideals (20)

Kürzlich hochgeladen

Kürzlich hochgeladen (20)

22 ideals