Kurt Nørmark
Department of Computer Science, Aalborg University, Denmark

Abstract Next lecture Index References Contents

In this introductory part of the material we will introduce the concept of programming paradigms.

It is interesting and useful to investigate the meaning of the word 'paradigm'

"An example that serves as pattern or model." The dictionary meaning of the word 'paradigm' comes from 'The American Heritage Dictionary of the English Language, Third Edition'.

"A philosophical and theoretical framework of a scientific school or discipline within which theories, laws, and generalizations and the experiments performed in support of them are formulated" This dictionary meaning of the word paradigm comes from 'The Merriam-Webster's Collegiate dictionary' - meaning 3 out of 3.

Programming paradigm (in this course) A pattern that serves as a school of thoughts for programming of computers Programming technique Related to an algorithmic idea for solving a particular class of problems Examples: 'Divide and conquer' and 'program development by stepwise refinement' Programming style The way we express ourselves in a computer program Related to elegance or lack of elegance Programming culture The totality of programming behavior, which often is tightly related to a family of programming languages The sum of a main paradigm, programming styles, and certain programming techniques.

The main programming paradigms Slide Annotated slide Contents Index References Textbook

We identify four main programming paradigms and a number of minor programming paradigms

The concept Main paradigm: A main programming paradigm stems an idea within some basic discipline which is relevant for performing computations

Main programming paradigms The imperative paradigm The functional paradigm The logical paradigm The object-oriented paradigm Other possible programming paradigms The visual paradigm One of the parallel paradigms The constraint based paradigm

Reference Foldoc: visual programming

First do this and next do that

Characteristics: Discipline and idea Digital hardware technology and the ideas of Von Neumann Incremental change of the program state as a function of time. Execution of computational steps in an order governed by control structures We call the steps for commands Straightforward abstractions of the way a traditional Von Neumann computer works Similar to descriptions of everyday routines, such as food recipes and car repair Typical commands offered by imperative languages Assignment, IO, procedure calls Language representatives Fortran, Algol, Pascal, Basic, C The natural abstraction is the procedure Abstracts one or more actions to a procedure, which can be called as a single command. "Procedural programming" We use several names for the computational steps in an imperative language. The word statement is often used with the special computer science meaning 'a elementary instruction in a source language'. The word instruction is another possibility; We prefer to devote this word the computational steps performed at the machine level. We will use the word 'command' for the imperatives in a high level imperative programming language. A procedure abstracts one or more actions to a procedure, which can be activated as a single action.

Reference Foldoc: imperative

Overview of the functional paradigm Slide Annotated slide Contents Index References Textbook

Evaluate an expression and use the resulting value for something

Characteristics: Discipline and idea Mathematics and the theory of functions The values produced are non-mutable Impossible to change any constituent of a composite value As a remedy, it is possible to make a revised copy of composite value Atemporal Time only plays a minor role compared to the imperative paradigm Applicative All computations are done by applying (calling) functions The natural abstraction is the function Abstracts a single expression to a function which can be evaluated as an expression Functions are first class values Functions are full-fledged data just like numbers, lists, ... Fits well with computations driven by needs Opens a new world of possibilities

Reference Foldoc: functional programming

Overview of the logic paradigm Slide Annotated slide Contents Index References Textbook

Answer a question via search for a solution

Characteristics: Discipline and idea Automatic proofs within artificial intelligence Based on axioms, inference rules, and queries. Program execution becomes a systematic search in a set of facts, making use of a set of inference rules

Reference Foldoc: logic programming

Overview of the object-oriented paradigm Slide Annotated slide Contents Index References Textbook

Send messages between objects to simulate the temporal evolution of a set of real world phenomena

Characteristics: Discipline and idea The theory of concepts, and models of human interaction with real world phenomena Data as well as operations are encapsulated in objects Information hiding is used to protect internal properties of an object Objects interact by means of message passing A metaphor for applying an operation on an object In most object-oriented languages objects are grouped in classes Objects in classes are similar enough to allow programming of the classes, as opposed to programming of the individual objects Classes represent concepts whereas objects represent phenomena Classes are organized in inheritance hierarchies Provides for class extension or specialization

Reference Foldoc: object-oriented programming

Chapter 1: Programming Paradigms
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