CSCI: 4500/6500 Programming Languages Origin & Evolution 1 - PDF document

CSCI: 4500/6500 Programming Languages Origin & Evolution 1 Maria Hybinette, UGA Programming Paradigm: Programming Paradigm: Imperative Declarative � � Not Imperative: Describes what computation should be performed and not how to compute it � � Imperative programming: Describes computation in terms of a � � Functional or Applicative, Programming: Treats computation as program state and statements that change the program state. � the evaluation of mathematical functions. » � Central features are variables, assignment statement and iterations � » � Reactive » � sequence of commands for the computer to perform » � emphasizes the definitions of functions rather than implementations of » � FORTRAN, Algol, Pascal, C state machines (idea is to apply functions to given parameters). » � von Neumann » � Can be done without assignment statements, and without iteration. � � Object Oriented programming: Computer program is composed » � Advantage: no side-effects of a collection of units, or objects that act on each other (instead » � Scheme, LISP, SM of a collection of functions. Each objects is capable of receiving a � � Logic programming: Defines “what” to be computed, rather than message, processing data and sending messages to other objects “how” the computation takes place. Example, in Prolog, you � � Scripting supply a database of facts and rules: and perform queries on the database. » � Goal directed: Contraints 3 4 Maria Hybinette, UGA Maria Hybinette, UGA First General Purpose Machine Ada Lovelace: First Programmer � � Charles Babbage designed the first computer, � � Worked with Babbage, the Analytical Engine, starting in 1823 never daughter of Lord Byron completed but build 100 years later � � Mathematician � � Created first program for the � � A store (memory) holding 1000 numbers Analytical Engine � � An arithmetical unit � � Assembly like language » � Plan for calculating Bernoulli � � Loops numbers � � Conditionals � � Language ADA named in her � � 3 types of punch cards (similar to ones that honor described patterns for weaving machines) » � one for arithmetical , constants, one for loads/store 5 6 Maria Hybinette, UGA Maria Hybinette, UGA

Zuse’s Plankalkül : First High- Level Programming Language Grace Hoper: The First Compiler � � Formulated a language using predicate � � Mathematical PhD Yale 1934 logic (Prolog like), boolean algebra and � � Wrote first compiler, the “A” data structures for his general purpose relay computer called the Z4 (which compliler for programming survived the war) around 1942-1945, � � Co-designer of COBOL not published until 1972. First compiler implemented in 2000 5 years after (Common Business Oriented Zuse’s death. Language) the most widely � � Assignment statements, subroutines, used programming language conditional statements, iteration, floating point, hierarchical records, until recently (1959). 1960 – assertions, exceptions handling, goal compiler built. Influenced by directed execution, arrays. Flowmatic. 7 8 Maria Hybinette, UGA Maria Hybinette, UGA First Major Language: First Computer Bug? FORTRAN Photo #: NH 96566-KN (Color) � The First "Computer Bug" � � � Developed by John Backus for IBM Moth found trapped between points at Relay # 70, Panel F, of the Mark II Aiken Relay 704 (1955) Calculator while it was being tested at � � Scientific Computing Harvard University, 9 September 1945. The operators affixed the moth to the computer � � Names could have up to six log, with the entry: "First actual case of bug characters being found". They put out the word that they had "debugged" the machine, thus � � Post-test counting loop ( DO ) introducing the term "debugging a computer program". � � � Formatted I/O In 1988, the log, with the moth still taped by � � User-defined subprograms the entry, was in the Naval Surface Warfare Center Computer Museum at Dahlgren, � � Three-way selection statement Virginia. � (arithmetic IF ) Courtesy of the Naval Surface Warfare � � No data typing statements Center, Dahlgren, VA., 1988. � U.S. Naval Historical Center Photograph. � http://www.history.navy.mil/photos/images/h96000/h96566kc.htm 10 Maria Hybinette, UGA Fortran II Fortran IV � � Distributed in 1958 � � Evolved during 1960-62 » � Independent compilation » � Explicit type declarations » � Fixed the bugs » � Logical selection statement » � Subprogram names could be parameters » � ANSI standard in 1966 11 12 Maria Hybinette, UGA Maria Hybinette, UGA

Fortran 77 Fortran 90 � � Became the new standard in 1978 � � Most significant changes from Fortran 77 » � Character string handling » � Modules » � Logical loop control statement » � Dynamic arrays » � IF-THEN-ELSE statement » � Pointers » � Recursion » � CASE statement » � Parameter type checking 13 14 Maria Hybinette, UGA Maria Hybinette, UGA Fortran Evaluation Functional Programming: LISP � � Highly optimizing compilers (all versions � � LISt Processing language (2 nd oldest high before 90) level programming language – FORTRAIN is oldest) » � Types and storage of all variables are fixed before run time » � Designed at MIT by McCarthy (1958) � � Dramatically changed forever the way � � AI research needed a language to computers are used » � Process data in lists (rather than arrays) » � Symbolic computation (rather than numeric) � � Only two data types: atoms and lists � � Syntax is based on Alonzo Church’s lambda calculus 15 16 Maria Hybinette, UGA Maria Hybinette, UGA Representation of Two LISP Lists 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 17 18 Maria Hybinette, UGA Maria Hybinette, UGA

Scheme COMMON LISP � � Developed at MIT in mid 1970s � � An effort to combine features of several dialects of LISP into a single language � � Small � � Large, complex � � Extensive use of static scoping � � Functions as first-class entities � � Simple syntax (and small size) make it ideal for educational applications 19 20 Maria Hybinette, UGA Maria Hybinette, UGA The First Step Toward Sophistication: Early Design Process ALGOL 60 � � Environment of development � � ACM and GAMM met for four days for design (May 27 to June 1, 1958) » � FORTRAN had (barely) arrived for IBM 70x » � Many other languages were being developed, all for � � Goals of the language specific machines » � Close to mathematical notation » � No portable language; all were machine- » � Good for describing algorithms dependent » � Must be translatable to machine code » � No universal language for communicating algorithms � � ALGOL 60 was the result of efforts to design a universal language 21 22 Maria Hybinette, UGA Maria Hybinette, UGA ALGOL 58 ALGOL 58 Implementation � � Concept of type was formalized � � Not meant to be implemented, but variations � � Names could be any length of it were (MAD, JOVIAL) � � Arrays could have any number of subscripts � � Although IBM was initially enthusiastic, all � � Parameters were separated by mode (in & out) support was dropped by mid 1959 � � 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” 23 24 Maria Hybinette, UGA Maria Hybinette, UGA