1. Programming Language History and Evolution
In Text: Chapter 2

2. An Overview of PL History
1950
1960
1970
1980
1990
2000
1950’s: Discovery and description
1960’s: Elaboration and analysis
1970’s: Technology
1980’s: New paradigms
1990’s: Internet influences
 Chapter 2: History and Evolution of Programming Languages 

3. 1950’s: Discovery and Description
FORTRAN
LISP
1950
1960
1970
1980
1990
2000
FORTRAN (54-57, and on and on):
First widely used compiled language
Relatively efficient
LISP (56-62):
First functional language, first support for recursion, activation records, run-time stack
First garbage collector, implicit dynamic memory mgmt.
Interpreter-based
 Chapter 2: History and Evolution of Programming Languages 

4. 1960’s: Elaboration and Analysis
ALGOL
COBOL
SNOBOL
APL
BASIC
PL/I
1950
1960
1970
1980
1990
2000
ALGOL 58, 60: first universal language. NEW: BNF, block structure, call-by-value, stack-based evaluation, stack-based arrays
APL: applicative, no precedence, interpreted
COBOL:English-style syntax, records in files
BASIC: interactive time-sharing terminals
SNOBOL: pattern matching
PL/I: the kitchen sink
 Chapter 2: History and Evolution of Programming Languages 

5.  Chapter 2: History and Evolution of Programming Languages 
1970’s: Technology
Pascal
Modula-2
Smalltalk
SIMULA 67 C
Prolog
1950
1960
1970
1980
1990
2000
SIMULA 67: classes, inheritance, data abstraction
Pascal: small, elegant, structured programming, teaching
C: systems programming, efficiency
Modula-2: Pascal + modules, better for systems programming
Prolog: first logic language, AI-oriented
Smalltalk: pure OO, interpreted, entire system
 Chapter 2: History and Evolution of Programming Languages 

6.  Chapter 2: History and Evolution of Programming Languages 
1980’s: New Paradigms
Ada
SML
C++
1950
1960
1970
1980
1990
2000
Ada: DoD, long committee-based development, large & complex, packages, tasks, generics, exceptions, from real-time to payroll apps.
C++: OOP in a popular, widespread language, often seen as a “hybrid”
Standard ML, Hope, Miranda, Haskell: functional languages
 Chapter 2: History and Evolution of Programming Languages 

7. 1990’s: Internet Influences
Perl
Java
1950
1960
1970
1980
1990
2000
Scripting: Perl, TCL, Visual Basic, JavaScript, Python, …
Java: designed for portable binaries and internet use, “clean” OO compared to C++, garbage collection, compiled/interpreted hybrid
 Chapter 2: History and Evolution of Programming Languages 

8.  Chapter 2: History and Evolution of Programming Languages 
Recap of Paradigms
Procedural/Imperative
Functional/Applicative
Logic
Object-oriented (closely related to imperative)
Problem-oriented/application-specific
 Chapter 2: History and Evolution of Programming Languages 

9. Overview: Procedural/Imperative
Describes how the computer should achieve solution
Key features:
Stored memory
Mutable variables
Sequencing, selection, iteration
Pointers?
 Chapter 2: History and Evolution of Programming Languages 

10. Overview: Functional/Applicative
Based on mathematics of recursive functions
Key features:
No mutable variables
Everything is an expression
Everything is a function
No iteration (loops)
Recursion, recursion, recursion!
 Chapter 2: History and Evolution of Programming Languages 

11.  Chapter 2: History and Evolution of Programming Languages 
Factorial in Scheme
; A factorial function in Scheme
(define (factorial N)
(if (<= N 1) 1
(* N (factorial (- N 1))) )
 Chapter 2: History and Evolution of Programming Languages 

12.  Chapter 2: History and Evolution of Programming Languages 
Overview: OOP
Based on procedural/imperative style, with added data+code abstraction & encapsulation
Key features:
Encapsulation
Inheritance
Polymorphism/dynamic binding
 Chapter 2: History and Evolution of Programming Languages 

13.  Chapter 2: History and Evolution of Programming Languages 
Overview: Logic
Based on predicate logic
Declarative: describes what problem is to be solved, but not how
Key features:
No mutable variables
Statements: implications or assertions
Every statement succeeds or fails
Few explicit control constructs
Recursion, recursion, recursion!
Must understand implementation model to use
 Chapter 2: History and Evolution of Programming Languages 

14.  Chapter 2: History and Evolution of Programming Languages 
Factorial in Prolog
/* A factorial predicate in Prolog */
factorial( N, 1 ) :- N <= 1.
factorial( N, F ) :-
N2 is N – 1,
factorial( N2, F2 ),
F is F2 * N.
 Chapter 2: History and Evolution of Programming Languages 

15.  Chapter 2: History and Evolution of Programming Languages 
Factorial in Prolog
/* A factorial predicate in Prolog.
* factorial( X, Y ) is true if
* Y == X! */
factorial( N, 1 ) :- N <= 1.
factorial( N, F ) :-
N2 is N – 1,
factorial( N2, F2 ),
F is F2 * N.
 Chapter 2: History and Evolution of Programming Languages 

16.  Chapter 2: History and Evolution of Programming Languages 
Factorial in Prolog
/* A different factorial predicate */
factorial( 0, 1 ).
factorial( N, F ) :-
N > 0,
N2 is N – 1,
factorial( N2, F2 ),
F is F2 * N.
 Chapter 2: History and Evolution of Programming Languages 

17.  Chapter 2: History and Evolution of Programming Languages 
Factorial in Scheme
; A factorial function in Scheme
(define (factorial N)
(cond
((= N 0) 1)
((> N 0)
(* N (factorial (- N 1)))) )
 Chapter 2: History and Evolution of Programming Languages 

18. Tail Recursion in Scheme
(define (factorial-helper N total)
(if (= N 0)
total
(factorial-helper (- N 1)
(* N total)) )
(define (factorial N)
(factorial-helper N 1)
 Chapter 2: History and Evolution of Programming Languages 