Programming Languages
• What is a programming language?
– systematic notation by which we describe computational processes to others
– notation for description of algorithms and data structures
computational process – set of steps solve a problem
• computer’s built-in abilities: PRIMITIVE/ constitute Machine
Language
– arithmetic and logical operations
– I/O
– Some “control” functions
• High-level programming languages – less primitive notations/ need
system software to translate
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Why study programming
languages?
• Linguistic theory states: structure of language
defines boundaries of thought
?TRUE?
• Language can facilitate or impede certain modes
of thought
• A given programming language can influence
class of solutions
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Benefits of studying languages?
• Computer Scientists
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Improve ability to develop algorithms
Improve existing use of language
Increase vocabulary of programming constructs
Allow choice of language
Easier to learn new language
Easier to design new language (user interfaces)
• Language Designers/Implementers
– insights from motivation of language facilities to make
implementation tradeoffs
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Benefits of studying languages?
• Hardware Architects
– gain insight into ways machines may better support languages
– design a semantically coherent machine w/ complete sets of data types and
operations
• System designers
– apply to human interfaces
– JCL’s, DB systems, editors, text formatters, debuggers have many characteristics of
a programming language
– Necessary for file systems, linkage editors to interface with programming languages
• Software Managers
– choice of language
– choice of extension of language or new language and know costs
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Early History
1500-3000 B.C. earliest know algorithm on clay tablets in
Babylon (near Baghdad, Iraq)
• produced mathematical tables
• solved algebraic equations using an “algorithm”
• at end put “this is the procedure”
• did not have conditional tests (no 0 or negative numbers)
• did have repetition
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Early History
• 300 B.C. Euclid Greece
– algorithm for computing GCD of 2 integers (zero still not recognized, so
special cases)
• 19th, early 20th century
– Charles Babbage English
– 2 machines:
• Difference Engine: finite differences, repeated additions, math tables
• Analytical Engine: many principles of modern computer, any calculation
Store = main memory
Mill=ALU
barrel = control unit
TABLE 1.2 on Handout – Influences on programming language development
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Early Computer programming
languages by category
• Numerical
• WWII 30/40s “electronic calculators” to solve numerical problems
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50s
symbolic notations/compilation necessary
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1955-57 Backus’ team – developed FORTRAN
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numerical calculations
full-fledged programming language (control structs, cond, I/O statements)
to compete w/ assembly made very efficient!
Extremely successful
1958 – Fortran II
Fortran IV
Fortran 77, 90 backwards compatible
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Early Computer programming
languages by category
• Success of FORTRAN -> fear in Europe of domination of IBM
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leader Naur of (German Math Society)
joined by ACM despite fear
ALGOL (Algorithmic Language) 58, 60
Standard in “academia”
GOALS (4)
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Close to standard math
Useful to describe algorithm
Compilable
Machine independent (no I/O)
– Not successful
– MAJOR IMPACT – syntactic notation BNF
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Early Computer programming
languages by category
• AI Languages
50s
– IPL – Info Processing language by Rand Corp (widely known, but use
limited)
– John McCarthy of MIT designed LISP (List Processing) for IBM 704
=> Scheme and Common Lisp
• list processing FUNCTIONAL Language
• usual problems: searching
text processing => SNOBOL
– Prolog – special purpose based on math logic
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Early Computer programming
languages by category
• Systems Languages
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Assembly language
CPL, BCPL – not widespread
C – Unix written mostly in C in 1970s
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ROLE of Programming Languages
•Early: efficient design
computers and time expensive vs programmers minor cost
• 60s: machines less expensive, programmers more
=> need portability, maintainability, ease of use
• programming languages evolving
• COBOL dropping => application generators
• APL, PL/1, SNOBOL – practically disappeared
• Pascal – past prime, but continued in Ada
• Ada – ground lost to C++ and Java
• Delphi and C++ Builder
• Fortran revised (for supercomputers)
Influences
• capabilities of computers
• applications: now games, PCs
• programming methods: environment changes,
good methods known now
• implementation methods -> effect choices of
features
• theory: deepened understanding of strengths and
weaknesses
• standards
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Historical Development of Java
C++
1983
Java
1991
Smalltalk-80
1980
Java 1
1995
Java 1.2
1998
Java 1.3
2000
Java 1.4
2002
Java 5.0
2005
Java SE 6
2007
Java SE 7 2011
7.25 2013
Java SE 8
Mar 2014
Scheme
1984
Lisp1.5
1962
Other references:
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http://www.java.com/en/javahistory/index.jsp
http://ils.unc.edu/blaze/java/javahist.html
http://ei.cs.vt.edu/~wwwbtb/book/chap1/java_hist.html
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Historical Languages
• C - general-purpose, imperative computer programming language
• C++- Based on C, but has imperative, objectoriented and generic programming feature
• Smalltalk - object-oriented, dynamically
typed, reflective programming language. It was designed and created
in part for educational use, more so for constructionist learning
• Lisp - practical mathematical notation for computer programs,
influenced by Church's lambda calculus. It quickly became the favored
programming language for artificial intelligence (AI) research
• Scheme - a minimalist, multi-paradigm dialect of Lisp
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Historical Development of Python
B
1981
Modula
1975
BCPL
1967
Modula 2
1979
ABC
1987
Modula 3
1988
B
1969
Pascal
1970
C
1971
Pascal AFNOR
1983
C (K&R)
1978
Reference:
http://www.levenez.com/lang
Python
1991
ANSI C
1989
Python 2
1999
Python3
2008
Ruby
1993
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Historical Languages
• BCPL - Originally intended for writing compilers for other languages
• B - recursive, non-numeric, machine independent applications, such
as system and language software
• C - general-purpose, imperative computer programming language
• Pascal - small and efficient language intended to encourage good
programming practices using structured programming and data
structuring.
• Modula - main innovation of Modula over Pascal is a module
system, used for grouping sets of related declarations into program
units
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