Programming Languages CS 430/CS 530 Fall 2004 Professor Adams

Programming Languages facilitate the expression and communication of ideas between people have a narrower expressive domain than natural languages because they only communicate algorithmic ideas enable communication of algorithms between people and computers Think of all the ways I could tell you to “leave me alone” and the nuances of each. Narrower expressive domain doesn’t have those nuances.

Required definition of an Algorithm An algorithm is an unambiguous, step-by-step procedure for solving a problem in a finite amount of time using a finite amount of space

Categories of Language Design Principles Syntax context-free grammar Type systems and semantics values that programs can manipulate meaning of programs Memory management Exception handling

Memory Management static memory dynamic memory stack heap lifetime of objects techniques for garbage collection & storage reclamation

Exceptions unexpected input unexpected divide by zero unexpected attempt to create a new block of space on the heap

Programming Paradigms Imperative Object-oriented Functional Logic (declarative) programming Event-driven programming Concurrent programming

Imperative Programming Explicit series of steps calculates, retrieves input, produces output Procedural abstraction assignments, loops, sequences, conditionals Major imperative languages Fortran (1954, IBM, John Backus), Cobol (Codasyl Committee), C (designed for and implemented on the UNIX operating system on the DEC PDP-11 by Dennis Ritchie) , C++, Ada

Object-Oriented Programming Program is a collection of objects which pass messages to one another to transform their states Object modeling, classification, inheritance are fundamental building blocks Major OO languages Smalltalk (Xerox PARC - Adele Goldberg & Alan Kay 1970’s), Java, C++, Eiffel

Functional Programming Program is a collection of mathematical functions input (domain) result (range) Functions interact & combine using functional composition, conditionals, recursion Major functional languages Lisp (John McCarthy – M.I.T. – late 50’s), Scheme (block structure, lexical scoping, etc.), Haskell, ML

Logic (declarative) Programming Program is a series of statements about what should happen rather than how it should be done Expresses non-determinism Major logic programming language Prolog(Alain Colmerauer – Universite d’Aix Marseilles – 1972)

Event-driven Programming Program is a continuous loop that responds to unpredictably ordered events Events originate from user actions (mouse clicks or keystrokes) sensors on a robot Major event-driven languages include Visual Basic, Java

Concurrent Programming Program is a collection of cooperating processes Concurrent Programming Languages SR, Linda, High Performance Fortran