Software ideals and historySoftware ideals and history
Bjarne StroustrupBjarne Stroustrupwww.stroustrup.com/Programmingwww.stroustrup.com/Programming
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 thanwhat we can cover)what we can cover)
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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 be There can be no professionalism without historyno professionalism without history
If you know too little of the background of your field you are If 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
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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
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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
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Geek heroesGeek heroes
Brian KernighanBrian Kernighan Programmer and writer Programmer and writer
extraordinaireextraordinaire
77
Dennis RitchieDennis Ritchie Designer and original Designer and original
implementer of Cimplementer of C
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Another geek heroAnother geek hero
Kristen NygaardKristen Nygaard Co-inventor (with Ole-Co-inventor (with Ole-
Johan Dahl) of Simula67 Johan Dahl) of Simula67 and of object-oriented and of object-oriented Programming and Programming and object-oriented designobject-oriented design
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Yet another geek heroYet another geek hero
Alex StepanovAlex Stepanov Inventor of the STL and Inventor of the STL and
generic programming generic programming pioneerpioneer
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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) and Both extremes encourage overstatement of results (hype) and understatement (or worse) of alternatives and ancestor languagesunderstatement (or worse) of alternatives and ancestor languages
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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 sense where and only where combinations make sense From these followFrom these follow
CorrectnessCorrectness MaintainabilityMaintainability PerformancePerformance
Apply these to the widest possible range of Apply these to the widest possible range of applicationsapplications
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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 see When 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 the this 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 the Don’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 are The bug is always where you are notnot looking – or you would have looking – or you would have
found it already”found it already”
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Ideals are personalIdeals are personal Chose yours wellChose yours well
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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, …
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Styles/paradigmsStyles/paradigmstemplate<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
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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
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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, …
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Early programming languagesEarly programming languages
1818
Classic C
Simula
Pascal
Algol68
BCPL
Fortran
Lisp
COBOL
Algol60
PL\1
1950s: 1960s: 1970s:
Red==major commercial useYellow==will produce important “offspring”
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Modern programming languagesModern programming languages
1919
Object Pascal
C++
Java95
C#Ada98
C++98
Java04
C++0x
PythonLispSmalltalk
Fortran77
Ada
EiffelSimula67
COBOL89
PHP
C89
Pascal
PERLVisual Basic
COBOL04 Javascript
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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 implement Over the decades, we learn better ways to design and implement
languageslanguages
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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 ))
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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
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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 the The 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 a A functional programming language called FP, which advocates a
mathematical approach to programmingmathematical approach to programming..
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Fortran – 1956Fortran – 1956 Allowed programmers to write linear algebra much as they Allowed 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 with Fortran code could often be moved from computer to computer with
only minor modificationonly minor modification This was a This was a hugehuge improvement improvement
Arguably the largest single improvement in the history of Arguably the largest single improvement in the history of programming languagesprogramming languages
Continuous evolution: II, IV, 77, 90, 0xContinuous evolution: II, IV, 77, 90, 0x
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COBOLCOBOL ““Rear Admiral Dr. Grace Murray Hopper (US Rear Admiral Dr. Grace Murray Hopper (US
Navy) was a remarkable woman who grandly Navy) was a remarkable woman who grandly rose to the challenges of programming the first rose to the challenges of programming the first computers. During her lifetime as a leader in computers. During her lifetime as a leader in the field of software development concepts, she the field of software development concepts, she contributed to the transition from primitive contributed to the transition from primitive programming techniques to the use of programming techniques to the use of sophisticated compilers. She believed that sophisticated 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.”
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Cobol – 1960Cobol – 1960 Cobol was (and sometimes still is) for business programmers Cobol was (and sometimes still is) for business programmers
what Fortran was (and sometimes still is) for scientific what 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 business It was hoped/claimed that Cobol was so close to business
English that managers could program and programmers would English 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
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LispLisp
John McCarthyJohn McCarthy Stanford UniversityStanford University AI pioneerAI pioneer
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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) the This 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++
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AlgolAlgol
Peter NaurPeter Naur Danish Technical University and RegnecentralenDanish Technical University and Regnecentralen BNFBNF
Edsger DijkstraEdsger Dijkstra Mathematisch Centrum, Amsterdam, Eindhoven University of Mathematisch 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
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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
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Algol58 Algol60
Simula67
Algol68
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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
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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 a A program becomes a set of interacting objects rather than a
monolithmonolith Has major (positive) implications for error ratesHas major (positive) implications for error rates
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CC Dennis RitchieDennis Ritchie Bell LabsBell Labs C and helped with UnixC and helped with Unix
Ken ThompsonKen Thompson Bell LabsBell Labs UnixUnix
3333
Doug McIlroyDoug McIlroy Bell LabsBell Labs Everybody’s favorite critic, Everybody’s favorite critic,
discussion partner, and discussion partner, and ideas man (influenced C, ideas man (influenced C, C++, Unix, and much C++, Unix, and much more)more)
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Bell Labs – Murray HillBell Labs – Murray Hill
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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, systems Very widely used, relatively low-level, weakly typed, systems
programming languageprogramming language Associated with Unix and through that with Linux and the open source Associated 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
3535
CPL BCPL B
C99
C++
C89
Classic C
C++98
Christopher Strachey, Cambridge, mid-1960s
Martin Richards, Cambridge, 1967
Ken Thompson, BTL, 1972
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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 and manageable making abstraction techniques affordable and manageable
for mainstream projects for mainstream projects pioneered the use of object-oriented and generic pioneered the use of object-oriented and generic
programming techniques in application areas where programming techniques in application areas where efficiency is a premium efficiency is a premium
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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 related in Elegance, efficiency, and correctness are closely related in
many application domainsmany application domains Inelegance/verbosity is a major source of bugs and inefficienciesInelegance/verbosity is a major source of bugs and inefficiencies
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C++ – 1985C++ – 1985
C++ is a general-purpose programming language C++ 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
3838
Classic C
Simula 67
C++C with Classes
C++98
ARM C++
1979-84
1978-89
1989
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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 and Programming 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 Programming History of Programming
Languages – IILanguages – II, Addison-Wesley, 1996, ISBN 0-201-89502-1, Addison-Wesley, 1996, ISBN 0-201-89502-1
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