2
Evolution Chapter of the Major Programming Languages
ISBN 0-321-33025-0
Chapter 2 Topics
Zuse's Plankalkul Minimal Hardware Programming: Pseudocodes The IBM 704 and Fortran Functional Programming: LISP The First Step Toward Sophistication: ALGOL 60 Computerizing Business Records: COBOL The Beginnings of Timesharing: BASIC
1-2
Copyright 2006 Addison-Wesley. All rights reserved.
Chapter 2 Topics (continued)
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 Programming Based on Logic: Prolog History's Largest Design Effort: Ada
1-3
Copyright 2006 Addison-Wesley. All rights reserved.
Chapter 2 Topics (continued)
ObjectOriented Programming: Smalltalk Combining Imperative ad ObjectOriented Features: C++ An ImperativeBased ObjectOriented Language: Java Scripting Languages: JavaScript, PHP, and Python A CBased Language for the New Millennium: C# Markup/Programming Hybrid Languages
1-4
Copyright 2006 Addison-Wesley. All rights reserved.
Genealogy of Common Languages
Copyright 2006 Addison-Wesley. All rights reserved.
1-5
Zuse's Plankalkl
Never implemented Advanced data structures Invariants
floating point, arrays, records
Copyright 2006 Addison-Wesley. All rights reserved.
1-6
Plankalkl Syntax
An assignment statement to assign the expression A[4] + 1 to A[5] | A + 1 => A V | 4 5 (subscripts) S | 1.n 1.n (data types)
Copyright 2006 Addison-Wesley. All rights reserved.
1-7
Minimal Hardware Programming: Pseudocodes
What was wrong with using machine code?
Poor readability Poor modifiability Expression coding was tedious Machine deficienciesno indexing or floating point
Copyright 2006 Addison-Wesley. All rights reserved.
1-8
Pseudocodes: Short Code
Short Code developed by Mauchly in 1949 for BINAC computers 01
Expressions were coded, left to right Example of operations:
02 ) 07 + 03 = 08 pause 04 / 09 (
06 abs value 1n (n+2)nd power 2n (n+2)nd root 4n if <= n 58 print and tab
Copyright 2006 Addison-Wesley. All rights reserved.
1-9
Pseudocodes: Speedcoding
Speedcoding developed by Backus in 1954 for IBM 701 Pseudo ops for arithmetic and math functions
Conditional and unconditional branching Autoincrement registers for array access Slow! Only 700 words left for user program
Copyright 2006 Addison-Wesley. All rights reserved.
1-10
Pseudocodes: Related Systems
The UNIVAC Compiling System
David J. Wheeler (Cambridge University)
Developed by a team led by Grace Hopper Pseudocode expanded into machine code
developed a method of using blocks of relocatable addresses to solve the problem of absolute addressing
Copyright 2006 Addison-Wesley. All rights reserved.
1-11
IBM 704 and Fortran
Fortran 0: 1954 not implemented Fortran I:1957
Designed for the new IBM 704, which had index registers and floating point hardware Environment of development
Computers were small and unreliable Applications were scientific No programming methodology or tools Machine efficiency was most important
Copyright 2006 Addison-Wesley. All rights reserved.
1-12
Design Process of Fortran
Impact of environment on design of Fortran I
No need for dynamic storage Need good array handling and counting loops No string handling, decimal arithmetic, or powerful input/output (commercial stuff)
Copyright 2006 Addison-Wesley. All rights reserved.
1-13
Fortran I Overview
First implemented version of Fortran
Names could have up to six characters Posttest counting loop (DO) Formatted I/O Userdefined subprograms Threeway selection statement (arithmetic IF) No data typing statements
Copyright 2006 Addison-Wesley. All rights reserved.
1-14
Fortran I Overview (continued)
First implemented version of FORTRAN
No separate compilation Compiler released in April 1957, after 18 worker years of effort Programs larger than 400 lines rarely compiled correctly, mainly due to poor reliability of 704 Code was very fast Quickly became widely used
Copyright 2006 Addison-Wesley. All rights reserved.
1-15
Fortran II
Distributed in 1958
Independent compilation Fixed the bugs
Copyright 2006 Addison-Wesley. All rights reserved.
1-16
Fortran IV
Evolved during 196062
Explicit type declarations Logical selection statement Subprogram names could be parameters ANSI standard in 1966
Copyright 2006 Addison-Wesley. All rights reserved.
1-17
Fortran 77
Became the new standard in 1978
Character string handling Logical loop control statement IF-THEN-ELSE statement
Copyright 2006 Addison-Wesley. All rights reserved.
1-18
Fortran 90
Most significant changes from Fortran 77
Modules Dynamic arrays Pointers Recursion CASE statement Parameter type checking
Copyright 2006 Addison-Wesley. All rights reserved.
1-19
Fortran Evaluation
Highly optimizing compilers (all versions before 90) Dramatically changed forever the way computers are used Characterized as the lingua franca of the computing world
Types and storage of all variables are fixed before run time
Copyright 2006 Addison-Wesley. All rights reserved.
1-20
Functional Programming: LISP
LISt Processing language
Designed at MIT by McCarthy
AI research needed a language to
Only two data types: atoms and lists Syntax is based on lambda calculus
Process data in lists (rather than arrays) Symbolic computation (rather than numeric)
Copyright 2006 Addison-Wesley. All rights reserved.
1-21
Representation of Two LISP Lists
Copyright 2006 Addison-Wesley. All rights reserved.
1-22
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
Copyright 2006 Addison-Wesley. All rights reserved.
1-23
Scheme
Developed at MIT in mid 1970s Small Extensive use of static scoping Functions as firstclass entities Simple syntax (and small size) make it ideal for educational applications
Copyright 2006 Addison-Wesley. All rights reserved.
1-24
COMMON LISP
An effort to combine features of several dialects of LISP into a single language Large, complex
Copyright 2006 Addison-Wesley. All rights reserved.
1-25
The First Step Toward Sophistication: ALGOL 60
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
ALGOL 60 was the result of efforts to design a universal language
Copyright 2006 Addison-Wesley. All rights reserved.
1-26
Early Design Process
ACM and GAMM met for four days for design (May 27 to June 1, 1958) Goals of the language
Close to mathematical notation Good for describing algorithms Must be translatable to machine code
Copyright 2006 Addison-Wesley. All rights reserved.
1-27
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"
Copyright 2006 Addison-Wesley. All rights reserved.
1-28
ALGOL 58 Implementation
Not meant to be implemented, but variations of it were (MAD, JOVIAL) Although IBM was initially enthusiastic, all support was dropped by mid 1959
Copyright 2006 Addison-Wesley. All rights reserved.
1-29
ALGOL 60 Overview
Modified ALGOL 58 at 6day meeting in Paris New features
Block structure (local scope) Two parameter passing methods Subprogram recursion Stackdynamic arrays Still no I/O and no string handling
Copyright 2006 Addison-Wesley. All rights reserved.
1-30
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 machineindependent language First language whose syntax was formally defined (BNF)
Copyright 2006 Addison-Wesley. All rights reserved.
1-31
ALGOL 60 Evaluation (continued)
Failure
Never widely used, especially in U.S. Reasons
Lack of I/O and the character set made programs non portable Too flexiblehard to implement Entrenchment of Fortran Formal syntax description Lack of support from IBM
Copyright 2006 Addison-Wesley. All rights reserved.
1-32
Computerizing Business Records: COBOL
Environment of development
UNIVAC was beginning to use FLOWMATIC USAF was beginning to use AIMACO IBM was developing COMTRAN
Copyright 2006 Addison-Wesley. All rights reserved.
1-33
COBOL Historical Background
Based on FLOWMATIC FLOWMATIC features
Names up to 12 characters, with embedded hyphens English names for arithmetic operators (no arithmetic expressions) Data and code were completely separate Verbs were first word in every statement
Copyright 2006 Addison-Wesley. All rights reserved.
1-34
COBOL Design Process
First Design Meeting (Pentagon) May 1959 Design goals
Design committee members were all from computer manufacturers and DoD branches Design Problems: arithmetic expressions? subscripts? Fights among manufacturers
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
Copyright 2006 Addison-Wesley. All rights reserved.
1-35
COBOL Evaluation
Contributions
First macro facility in a highlevel language Hierarchical data structures (records) Nested selection statements Long names (up to 30 characters), with hyphens Separate data division
Copyright 2006 Addison-Wesley. All rights reserved.
1-36
COBOL: DoD Influence
First language required by DoD Still the most widely used business applications language
would have failed without DoD
Copyright 2006 Addison-Wesley. All rights reserved.
1-37
The Beginning of Timesharing: BASIC
Designed by Kemeny & Kurtz at Dartmouth Design Goals:
Current popular dialect: Visual BASIC First widely language used with time sharing
Copyright 2006 Addison-Wesley. All rights reserved. 1-38
Easy to learn and use for nonscience students Must be "pleasant and friendly" Fast turnaround for homework Free and private access User time is more important than computer time
2.8 Everything for Everybody: PL/I
Designed by IBM and SHARE Computing situation in 1964 (IBM's point of view)
Scientific computing
IBM 1620 and 7090 computers FORTRAN SHARE user group IBM 1401, 7080 computers COBOL GUIDE user group
1-39
Business computing
Copyright 2006 Addison-Wesley. All rights reserved.
PL/I: Background
By 1963
Scientific users began to need more elaborate I/O, like COBOL had; business users began to need floating point and arrays It looked like many shops would begin to need two kinds of computers, languages, and support stafftoo costly Build a new computer to do both kinds of applications Design a new language to do both kinds of applications
1-40
The obvious solution
Copyright 2006 Addison-Wesley. All rights reserved.
PL/I: Design Process
Designed in five months by the 3 X 3 Committee Initial concept
Three members from IBM, three members from SHARE An extension of Fortran IV
Initially called NPL (New Programming Language) Name changed to PL/I in 1965
Copyright 2006 Addison-Wesley. All rights reserved.
1-41
PL/I: Evaluation
PL/I contributions
First unitlevel concurrency First exception handling Switchselectable recursion First pointer data type First array cross sections
Concerns
Many new features were poorly designed Too large and too complex
Copyright 2006 Addison-Wesley. All rights reserved.
1-42
Two Early Dynamic Languages: APL and SNOBOL
Characterized by dynamic typing and dynamic storage allocation Variables are untyped Storage is allocated to a variable when it is assigned a value
A variable acquires a type when it is assigned a value
Copyright 2006 Addison-Wesley. All rights reserved.
1-43
APL: A Programming Language
Designed as a hardware description language at IBM by Ken Iverson around 1960
Still in use; minimal changes
Highly expressive (many operators, for both scalars and arrays of various dimensions) Programs are very difficult to read
Copyright 2006 Addison-Wesley. All rights reserved.
1-44
SNOBOL
Designed as a string manipulation language at Bell Labs by Farber, Griswold, and Polensky Powerful operators for string pattern matching Slower than alternative languages (and thus no longer used for writing editors) Stilled used for certain text processing tasks
Copyright 2006 Addison-Wesley. All rights reserved.
1-45
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
Coroutines 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
Copyright 2006 Addison-Wesley. All rights reserved.
1-46
Orthogonal Design: ALGOL 68
From the continued development of ALGOL 60 but not a superset of that language Source of several new ideas (even though the language itself never achieved widespread use) Design is based on the concept of orthogonality
A few principle concepts, few combining mechanisms
Copyright 2006 Addison-Wesley. All rights reserved.
1-47
ALGOL 68 Evaluation
Contributions
Userdefined data structures Reference types Dynamic arrays (called flex arrays) Less usage than ALGOL 60 Had strong influence on subsequent languages, especially Pascal, C, and Ada
Comments
Copyright 2006 Addison-Wesley. All rights reserved.
1-48
Early Descendants of ALGOLs
ALGOL languages impacted all imperative languages
Pascal C Modula/Modula 2 Ada Oberon C++/Java Perl (to some extent)
Copyright 2006 Addison-Wesley. All rights reserved.
1-49
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 mid1970s until the late 1990s, it was the most widely used language for teaching programming
Copyright 2006 Addison-Wesley. All rights reserved.
1-50
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
Copyright 2006 Addison-Wesley. All rights reserved.
1-51
Perl
Related to ALGOL only through C A scripting language
Developed by Larry Wall Perl variables are statically typed and implicitly declared Powerful but somewhat dangerous Widely used as a general purpose language
A script (file) contains instructions to be executed Other examples: sh, awk, tcl/tk
Three distinctive namespaces, denoted by the first character of a variable's name
Copyright 2006 Addison-Wesley. All rights reserved.
1-52
Programming Based on Logic: Prolog
Developed, by Comerauer and Roussel (University of AixMarseille), with help from Kowalski ( University of Edinburgh) Based on formal logic Nonprocedural 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
Copyright 2006 Addison-Wesley. All rights reserved. 1-53
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
Copyright 2006 Addison-Wesley. All rights reserved.
1-54
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...