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Chapter 2 Evolution of Major Programming Languages

Chapter 2 Evolution of Major Programming Languages. Fall 2014. Genealogy of Common Languages. Minmial Hardware Programming with Pseudocodes. Why programming with machine code is not good? MIPS instruction: add $t0,$t1,$t8 Binary code: 00000001001110000100000000100000

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Chapter 2 Evolution of Major Programming Languages

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  1. Chapter 2Evolution of Major Programming Languages Fall 2014 CS 1621

  2. Genealogy of Common Languages PITT CS 1621

  3. Minmial Hardware Programming withPseudocodes • Why programming with machine code is not good? MIPS instruction: add $t0,$t1,$t8 Binary code: 00000001001110000100000000100000 • Poor readability • What does the code want to do? • Poor modifiability • Want to change “a= b+1” to “a=c+2” • Expression coding was tedious • Instruction format, length, …. • Machine deficiencies--no indexing or floating point PITT CS 1621

  4. Pseudocodes • Short code • Mauchly in1949 for BINAC computers 01 – 06 abs value 1n (n+2)nd power 02 ) 07 + 2n (n+2)nd root 03 = 08 pause 4n if <= n 04 / 09 ( 58 print and tab “00 x0 03 20 06 Y0” ; X0=SQRT(ABS(Y0)) • Interpreted, 50 slower • Speedcoding • Backus in 1954 for IBM 701 • Handle --- branches, auto-increment register, floating-point operation • Interpreted • Memory has 700 usable words PITT CS 1621

  5. Punched card PITT CS 1621

  6. Fortran • Came with IBM 704 system • Index register and floating point instructions • Fortran I: 1957 • Environment of development • Computers were small and unreliable • Applications were scientific • No programming methodology or tools • Machine efficiency was most important • Impacts • No need for dynamic storage • Need good array handling and counting loops • No string handling, decimal arithmetic, or powerful input/output (commercial stuff) PITT CS 1621

  7. Fortran I Overview • First implemented version • If-stmt: if (e) N1, N2, N3 • Do-stmt: Do N1 v=V1, V2 • Posttest • User-defined routines • No data typing stmts • Names start with I,J,K,L,M are integer types, others floating point • Fast compiled code • Programs larger than 400 lines rarely compiled • IBM 704 was not reliable • Widely accepted after the introduction PITT CS 1621

  8. Fortran II, IV, 77 • Fortran II • Distributed in 1958 • Independent compilation and bug fix • Fortran IV • Type declaration • Logical selection • Passing subprogram as parameters • Evolve during 1960-62, ANSI standard in 1966 • Fortran 77 • Character string • Logical loop control • If-then-else-stmt • New starndard in 1978 PITT CS 1621

  9. Fortran 77 Example • Euclid.f (FORTRAN 77) * Find greatest common divisor using the Euclidean algorithm PROGRAM EUCLID PRINT *, 'A?' READ *, NA IF (NA.LE.0) THEN PRINT *, 'A must be a positive integer.' STOP END IF PRINT *, 'B?' READ *, NB IF (NB.LE.0) THEN PRINT *, 'B must be a positive integer.' STOP END IF PRINT *, 'The GCD of', NA, ' and', NB, ' is', NGCD(NA, NB), '.' STOP END FUNCTION NGCD(NA, NB) IA = NA IB = NB 1 IF (IB.NE.0) THEN ITEMP = IA IA = IB IB = MOD(ITEMP, IB) GOTO 1 END IF NGCD = IA RETURN END PITT CS 1621

  10. Fortran 90 • Significant changes • Modules • Dynamic arrays • Pointers • Recursion • Case-stmt • Parameter type checking PITT CS 1621

  11. Fortran Evaluation • Highly optimizing compilers • For all versions before Fortran 90 • Types and storage of all variables are fixed at compile-time • Less flexible but very efficient • The first widely used high-level language • Changed forever the way computers are used • Characterized as the lingua franca of the computing world PITT CS 1621

  12. Functional Programming: LISP • LISt Processing language • Designed at MIT by McCarthy • Based on lambda calculus • AI research needed a language to • Process data in lists (rather than arrays) • Symbolic computation (rather than numeric) • Only two data types • atoms and lists • Examples: ( A B C D) ? PITT CS 1621

  13. Example (DEFUN Equal_lst (lst1 lst2) (COND ( (ATOM lst1) (EQ lst1 lst2) ) ( (ATOM lst2) nil ) ( ( Equal_lst (CAR lst1) (CAR lst2) ) ( Equal_lst (CDR lst1) (CDR lst2) ) ) ( T nil) ) ) PITT CS 1621

  14. LISP Evaluation • Pioneered functional programming • No need for variables or assignment • Control via recursion and conditional expressions • Still the dominant language for AI • COMMON LISP and Scheme are contemporary dialects of LISP • ML, Miranda, and Haskell are related languages PITT CS 1621

  15. Scheme and COMMON LISP • Scheme • Developed at MIT in mid 1970s • Small • Extensive use of static scoping • Functions as first-class entities • Simple syntax (and small size) make it ideal for educational applications • COMMON LISP • An effort to combine features of several dialects of LISP into a single language • Large, complex PITT CS 1621

  16. The First Step Toward Sophistication • To design a universal language ? • Environment of development • FORTRAN had (barely) arrived for IBM 70x • Many other languages were being developed, all for specific machines • No portable language; all were machine-dependent • No universal language for communicating algorithms • International ALGOrithmic Language PITT CS 1621

  17. ALGOL 58 • Concept of type was formalized • Names could be any length • Arrays could have any number of subscripts • Parameters were separated by mode (in & out) • Subscripts were placed in brackets • Compound statements (begin ... end) • Semicolon as a statement separator • Assignment operator was := • if had an else-if clause • No I/O - “would make it machine dependent” • Not meant to be implemented • IBM dropped its support in mid 1959 PITT CS 1621

  18. ALGOL 60 Overview • Modified ALGOL 58 at 6-day meeting in Paris • New features • Block structure (local scope) • Two parameter passing methods • Subprogram recursion • Stack-dynamic arrays • Still no I/O and no string handling PITT CS 1621

  19. ALGOL 60 Evaluation • Successes • It was the standard way to publish algorithms for over 20 years • All subsequent imperative languages are based on it • First machine-independent language • First language whose syntax was formally defined (BNF) • Failure • Never widely used, especially in U.S. • Reasons • Lack of I/O and the character set made programs non-portable • Too flexible--hard to implement ALGOL68 • Formal syntax description • Lack of support from IBM PITT CS 1621

  20. Example BNF: <block>  <decl><stmt-lst> < stmt-lst>  <stmt-lst> <stmt><stmt>  <assign-stmt> | <for-stmt> | … <for-stmt>  for <assign-stmt> step <int-var> until <int-var> do <block> Program: begin integer array intlst[1:99]; integer listlen, counter, sum, average, result; sum: =0; … for counter:=1 step 1 until listlen do begin readint (intlst[counter]); … end; end PITT CS 1621

  21. Computerizing Business Records: COBOL • Environment of development • UNIVAC was beginning to use FLOW-MATIC • USAF was beginning to use AIMACO • IBM was developing COMTRAN PITT CS 1621

  22. COBOL Designs • First Design Meeting (Pentagon) - May 1959 • Design goals • Must look like simple English • Must be easy to use, even if that means it will be less powerful • Must broaden the base of computer users • Must not be biased by current compiler problems • Design committee members were all from computer manufacturers and DoD branches • Design Problems: arithmetic expressions? subscripts? Fights among manufacturers PITT CS 1621

  23. COBOL Evaluation • Contributions • First macro facility in a high-level language • Hierarchical data structures (records) • Nested selection statements • Long names (up to 30 characters), with hyphens • Separate data division • First language required by DoD • would have failed without DoD • Still the widely used business applications language PITT CS 1621

  24. PITT CS 1621

  25. Everything for Everybody: PL/I • Computing situation in 1964 (IBM's point of view) • Scientific computing • IBM 1620 and 7090 computers • FORTRAN • SHARE user group • Business computing • IBM 1401, 7080 computers • COBOL • GUIDE user group • Solution • Build a new computer for both • Design a new language for both PITT CS 1621

  26. PL/I: Evaluation • PL/I contributions • First unit-level concurrency • First exception handling • Switch-selectable recursion • First pointer data type • First array cross sections • Concerns • Many new features were poorly designed • Too large and too complex PITT CS 1621

  27. The Beginning of Timesharing: BASIC • Designed by Kemeny & Kurtz at Dartmouth • Design Goals: • Easy to learn and use for non-science students • Must be “pleasant and friendly” • Fast turnaround for homework • Free and private access • User time is more important than computer time • Current popular dialect: Visual BASIC • First widely used language with time sharing PITT CS 1621

  28. PITT CS 1621

  29. The Beginning of Data Abstraction:SIMULA 67 • Designed primarily for system simulation in Norway by Nygaard and Dahl • Based on ALGOL 60 and SIMULA I • Primary Contributions • Co-routines - a kind of subprogram • Implemented in a structure called a class • Classes are the basis for data abstraction • Classes are structures that include both local data and functionality PITT CS 1621

  30. Orthogonal Design: ALGOL 68 • The continued development of ALGOL 60 but not a superset • Source of several new ideas • based on the concept of orthogonality • Contributions • User-defined data structures • Reference types • Dynamic arrays (called flex arrays) • Impacted all imperative languages • Pascal, C, Modula/Modula 2, Ada, C++/Java, Perl PITT CS 1621

  31. Pascal - 1971 • Developed by Wirth (a member of the ALGOL 68 committee) • Designed for teaching structured programming • Small, simple, nothing really new • Largest impact on teaching programming • From mid-1970s until the late 1990s, it was the most widely used language for teaching programming PITT CS 1621

  32. C - 1972 • Designed for systems programming (at Bell Labs by Dennis Richie) • Evolved primarily from BCLP, B, but also ALGOL 68 • Powerful set of operators, but poor type checking • Initially spread through UNIX • Many areas of application PITT CS 1621

  33. Perl • Related to ALGOL only through C • A scripting language • A script (file) contains instructions to be executed • Other examples: sh, awk, tcl/tk • Developed by Larry Wall • Perl variables are statically typed and implicitly declared • Three distinctive namespaces, denoted by the first character of a variable’s name • Powerful but somewhat dangerous • Widely used as a general purpose language PITT CS 1621

  34. PITT CS 1621

  35. Programming Based on Logic: Prolog • Developed, by Comerauer and Roussel (University of Aix-Marseille), with help from Kowalski ( University of Edinburgh) • Based on formal logic • Non-procedural • Can be summarized as being an intelligent database system that uses an inferencing process to infer the truth of given queries • Highly inefficient, small application areas PITT CS 1621

  36. man(adam). man(peter). man(paul).   woman(marry). woman(eve). parent(adam,peter). % means adam is parent of peter parent(eve,peter). parent(adam,paul). parent(marry,paul). father(F,C):-man(F),parent(F,C). mother(M,C):-woman(M),parent(M,C). ?-father(X,paul). PITT CS 1621

  37. History’s Largest Design Effort: Ada • Huge design effort, involving hundreds of people, much money, and about eight years • Strawman requirements (April 1975) • Woodman requirements (August 1975) • Tinman requirements (1976) • Ironman equipments (1977) • Steelman requirements (1978) • Named Ada after Augusta Ada Byron, known as being the first programmer PITT CS 1621

  38. Ada Evaluation • Contributions • Packages - support for data abstraction • Exception handling - elaborate • Generic program units • Concurrency - through the tasking model • Comments • Competitive design • Included all that was then known about software engineering and language design • First compilers were very difficult; the first really usable compiler came nearly five years after the language design was completed PITT CS 1621

  39. Ada 95 • Ada 95 (began in 1988) • Support for OOP through type derivation • Better control mechanisms for shared data • New concurrency features • More flexible libraries • Popularity suffered because the DoD no longer requires its use but also because of popularity of C++ PITT CS 1621

  40. PITT CS 1621

  41. Object-Oriented Programming:Smalltalk • Developed at Xerox PARC, initially by Alan Kay, later by Adele Goldberg • First full implementation of an object-oriented language (data abstraction, inheritance, and dynamic type binding) • Pioneered the graphical user interface design • Promoted OOP PITT CS 1621

  42. Combining Imperative and Object-Oriented Programming: C++ • Developed at Bell Labs by Stroustrup in 1980 • Evolved from C and SIMULA 67 • Facilities for object-oriented programming, taken partially from SIMULA 67 • Provides exception handling • A large and complex language, in part because it supports both procedural and OO programming • Rapidly grew in popularity, along with OOP • ANSI standard approved in November 1997 • Microsoft’s version (released with .NET in 2002): Managed C++ • delegates, interfaces, no multiple inheritance PITT CS 1621

  43. Related OOP Languages • Objective-C (designed by Brad Cox – early 1980s) • C plus support for OOP based on Smalltalk • Uses Smalltalk’s method calling syntax • Used by Apple for systems programs • Delphi (Borland) • Pascal plus features to support OOP • More elegant and safer than C++ • Go (designed at Google - 2009) • Loosely based on C, but also quite different • Does not support traditional OOP 43

  44. An Imperative-Based Object-Oriented Language: Java • Developed at Sun in the early 1990s • C and C++ were not satisfactory for embedded electronic devices • Based on C++ • Significantly simplified (does not include struct, union, enum, pointer arithmetic, etc.) • Supports only OOP • Has references, but not pointers • Includes support for applets and a form of concurrency PITT CS 1621

  45. Java Evaluation • Eliminated unsafe features of C++ • Concurrency features • Libraries for applets, GUIs, database access • Portable: Java Virtual Machine concept, JIT compilers • Widely used for WWW pages • Use for other areas increased faster than any other language PITT CS 1621

  46. Scripting Languages for the Web • JavaScript • A joint venture of Netscape and Sun Microsystems • Used in Web programming (client side) to create dynamic HTML documents • Related to Java only through similar syntax • PHP • PHP: Hypertext Preprocessor • Used for Web applications (server side); produces HTML code as output • Python • An OO interpreted scripting language • Type checked but dynamically typed • Supports CGI and form processing PITT CS 1621

  47. Javascript • Dynamic typing • X=10;…..; x=“ten”; • 8+8=? … … 8+”8”=? …… “8”+8 =? • Embbed Javascript example PITT CS 1621

  48. PHP Example • Server side script vs Client side script • What is the response from the server? PITT CS 1621

  49. A C-Based Language for the New Millennium: C# • Part of the .NET development platform • Based on C++ , Java, and Delphi • Provides a language for component-based software development • All .NET languages (C#, Visual BASIC.NET, Managed C++, J#.NET, and Jscript.NET) use Common Type System (CTS), which provides a common class library • Likely to become widely used PITT CS 1621

  50. Markup/Programming Hybrid Languages • XSLT • eXtensible Markup Language (XML): a metamarkup language • eXtensible Stylesheet Language Transformation (XSTL) transforms XML documents for display • Programming constructs (e.g., looping) • JSP • Java Server Pages: a collection of technologies to support dynamic Web documents • servlet: a Java program that resides on a Web server; servlet’s output is displayed by the browser PITT CS 1621

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