Transcript Chapter 2: Evolution of the Major Programming Languages Lectures

Chapter 2: Evolution of the Major
Programming Languages
Lectures # 5
Chapter 2: Evolution of the Major
Programming Languages
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The IBM 704 and Fortran
Functional Programming: Lisp
The First Step Toward Sophistication: Algol 60
Computerizing Business Records: COBOL
The Beginnings of Timesharing: BASIC
Everything for Everybody: PL/I
Two Early Dynamic Languages: APL and SNOBOL
The Beginnings of Data Abstraction: SIMULA 67
Orthogonal Design: ALGOL 68
Some Early Descendants of the ALGOLs
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Chapter 2: Evolution of the Major
Programming Languages
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Programming Based on Logic: Prolog
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History’s Largest Design Effort: Ada
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Object-Oriented Programming: Smalltalk
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Combining Imperative and Object-Oriented Programming: C++
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An Imperative-Based Object-Oriented Language: Java
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Scripting Languages for the Web
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A C-Based Language for the New Millennium: C#
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Markup/Programming Hybrid Languages
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IBM 704 and Fortran
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Fortran 0 : 1954 - not implemented
Fortran I : 1957
 Designed for IBM 704.
 First implemented and compiled high level language.
 Variable names could have up to six characters.
 I/O formatting.
 User-defined subprograms.
 IF selection statement.
 DO loop statement.
 No data typing statements.
Fortran II : 1958
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Independent compilation of subprograms.
Fixed the bugs in Fortran I.
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IBM 704 and Fortran (cont.)
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Fortran IV : 1960-1962
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Fortran 77
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Explicit type declarations.
Logical IF selection statement.
Passing Subprograms as parameters to other subprograms.
Character string handling.
Logical loop control statement.
IF-THEN-ELSE statements.
Fortran 9X
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Dynamic arrays and Pointers.
Recursion.
CASE statement.
Parameter type checking.
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Functional Programming: LISP
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LIST Processing language.
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Needed by AI researchers to:
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Process data in lists (rather than arrays).
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Symbolic computation (rather than numeric).
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Only two data types: atoms and lists.
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Syntax is based on lambda calculus.
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Other Functional Programming
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Scheme: Developed at MIT in mid 1970s.
 Small size.
 Extensive use of static scoping.
 Treatment of functions as first-class entities (functions
can be assigned to variables, passed as parameters, and
returned as values).
 Simple syntax make it ideal for educational applications.
COMMON LISP
 An effort to combine features of several dialects of LISP
into a single language.
 Large and complex language.
ML, Miranda, and Haskell are related languages.
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The First Step Toward Sophistication:
Algol 60 (Algorithmic Language)
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Algol 58: Added several new constructs to Fortran.
 Identifiers could be any length.
 Arrays could have any number of subscripts.
 Parameters were separated by mode (in & out).
 Compound statements (begin ... end).
Algol 60
 Two parameter passing methods.
 Subprogram recursion.
 Stack-dynamic arrays.
 First machine-independent language.
 First language whose syntax was formally defined (BNF).
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Computerizing Business Records:
COBOL
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Based on FLOW-MATIC features such as:
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Names up to 12 characters, with embedded hyphens.
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English names for arithmetic operators.
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Data and code were completely separate.
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Hierarchical data structures (records).
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Nested selection statements.
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Long names (up to 30 characters), with hyphens.
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Separate data division.
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The Beginnings of Timesharing:
BASIC
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Based on Fortran with some influence from Algol 60.
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Easy to learn and use for non-science students.
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Pleasant and friendly.
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Free and private access.
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User time is more important than computer time.
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Current: Visual BASIC.
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First widely used language with time sharing.
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Everything for Everybody: PL/I
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Designed to be used in both business and scientific
applications.
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First allowed to create concurrently executing subprograms,
but it was poorly developed in PL/I.
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First exception handling.
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Used recursion.
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First pointers were included as a data type.
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Two Early Dynamic Languages:
APL and SNOBOL
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APL (A Programming Language)
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Characterized by dynamic typing and dynamic storage allocation
Variables are untyped.
 A variable acquires a type when it is assigned a value.
Storage is allocated to a variable when it is assigned a value.
Highly expressive (many operators, for both scalars and arrays of
various dimensions).
SNOBOL
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Designed as a string manipulation (text processing) language.
Powerful operators for string pattern matching.
Slower than alternative languages.
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The Beginnings of Data Abstraction:
SIMULA 67
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Designed primarily for system simulation.
Based on ALGOL 60 and SIMULA I.
New features:
 Coroutines - a kind of subprograms:
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Subprograms are allowed to restart at the position where
they previously stopped.
Implemented in a structure called a class.
Classes are the basis for data abstraction.
Classes are structures that include both local data and
functions.
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Orthogonal Design: ALGOL 68
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Design is based on the concept of orthogonality:
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A few principle concepts, few combining mechanisms.
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Had strong influence on subsequent languages, such as Pascal,
C, Modula 2, Ada, C++, Java, and Perl.
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New features:
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User-defined data structures.
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Reference types.
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Dynamic arrays (called flex arrays).
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Some Early Descendants of the
ALGOLs
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Pascal - 1971
 Designed for teaching structured programming.
 Small, simple, nothing really new.
 Largest impact on teaching programming.
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From mid-1970s until the late 1990s.
C – 1972
 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.
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Programming Based on Logic:
Prolog
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Based on formal logic.
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Non-procedural.
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Can be summarized as being an intelligent database system
that uses an inference process to infer the truth of given
queries.
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Highly inefficient, small application areas.
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History’s Largest Design Effort:
Ada
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New features:
 Packages - support for data abstraction.
 Exception handling  Generic program units.
 Concurrency - through the tasking model.
Ada 95 (began in 1988)
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Support for OOP through type derivation.
Better control mechanisms for shared data.
New concurrency features.
More flexible libraries.
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Object-Oriented Programming:
Smalltalk
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First full implementation of an object-oriented language (data
abstraction, inheritance, and dynamic type binding).
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Pioneered the graphical user interface design.
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Promoted OOP.
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Combining Imperative and ObjectOriented Programming: C++
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Evolved from C and SIMULA 67.
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Facilities for object-oriented programming, taken partially
from SIMULA 67.
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Provides exception handling.
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A large and complex language, in part because it supports
both procedural and OO programming.
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Rapidly grew in popularity, along with OOP.
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ANSI standard approved in November 1997.
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Microsoft’s version (released with .NET in 2002).
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Related OOP Languages
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Eiffel (designed by Bertrand Meyer - 1992)
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Not directly derived from any other language.
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Smaller and simpler than C++, but still has most of the
power.
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Lacked popularity of C++ because many C++ enthusiasts
were already C programmers.
Delphi (Borland)
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Pascal plus features to support OOP.
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More elegant and safer than C++.
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An Imperative-Based ObjectOriented Language: Java
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Based on C++
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Significantly simplified (does not include struct,
union, enum, pointer).
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Supports only OOP.
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Has references, but not pointers.
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Includes support for applets and a form of concurrency.
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An Imperative-Based ObjectOriented Language: Java (cont.)
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Java Evaluation:
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Eliminated unsafe features of C++.
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Concurrency features.
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Libraries for applets, GUIs, database access.
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Portable: Java Virtual Machine concept, JIT compilers.
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Widely used for WWW pages.
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Use for other areas increased faster than any other language.
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Most recent version, 5.0, released in 2004.
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Scripting Languages for the Web
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JavaScript
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PHP
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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: Hypertext Preprocessor.
Used for Web applications (server side); produces HTML code
as output.
Python
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An OO interpreted scripting language.
Type checked but dynamically typed.
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A C-Based Language for the New
Millennium: C#
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Part of the .NET development platform.
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Based on C++ , Java, and Delphi.
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Provides a language for component-based software
development.
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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.
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Likely to become widely used.
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Markup/Programming Hybrid
Languages
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XSLT
 eXtensible Markup Language (XML): a metamarkup language.
 eXtensible Stylesheet Language Transformation (XSLT)
transforms XML documents to XHTML documents for display.
 Programming constructs (e.g., looping).
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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.
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