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Programming paradigm
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A programming paradigm is a fundamental style of computer programming. (Compare with a methodology, which is a style of solving specific software engineering problems). Paradigms differ in the concepts and abstractions used to represent the elements of a program (such as objects, functions, variables, constraints, etc.) and the steps that compose a computation (assignation, evaluation, continuations, data flows, etc.).
class="link1" onMouseover='showByLink("m871446",this)' onMouseout='hide("m871446")'href="http://www.absoluteastronomy.com/topics/Programming_language">programming language can support multiple paradigms.
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A programming paradigm is a fundamental style of computer programming. (Compare with a methodology, which is a style of solving specific software engineering problems). Paradigms differ in the concepts and abstractions used to represent the elements of a program (such as objects, functions, variables, constraints, etc.) and the steps that compose a computation (assignation, evaluation, continuations, data flows, etc.).
Overview
A programming language can support multiple paradigms. For example programs written in C++ or Object Pascal can be purely procedural, or purely object-oriented, or contain elements of both paradigms. Software designers and programmers decide how to use those paradigm elements.
In object-oriented programming, programmers can think of a program as a collection of interacting objects, while in functional programming a program can be thought of as a sequence of stateless function evaluations. When programming computers or systems with many processors, process-oriented programming allows programmers to think about applications as sets of concurrent processes acting upon logically shared data structures.
Just as different groups in software engineering advocate different methodologies, different programming languages advocate different programming paradigms. Some languages are designed to support one particular paradigm (Smalltalk supports object-oriented programming, Haskell supports functional programming), while other programming languages support multiple paradigms (such as Object Pascal, C++, C#, Visual Basic, Common Lisp, Scheme, Perl,Python, Ruby and Oz).
Many programming paradigms are as well known for what techniques they forbid as for what they enable. For instance, pure functional programming disallows the use of side-effects; structured programming disallows the use of the goto statement. Partly for this reason, new paradigms are often regarded as doctrinaire or overly rigid by those accustomed to earlier styles. Avoiding certain techniques can make it easier to prove theorems about a program's correctness—or simply to understand its behavior.
History
Initially, computers were
programmed using binary code that represented control sequences fed to the computer CPU. This was difficult and error-prone. Programs written in binary are said to be written in machine code, which is a very
low-level programming paradigm.
To make programming easier, assembly languages were developed. These replaced
machine code functions with mnemonics and memory addresses with labels. Assembly language
programming is also a low-level paradigm although it is a second generation paradigm.
Although assembly language is an improvement over machine code, it is still prone to
errors, and difficult to debug and maintain.
The next advance was the development of procedural languages. These third-generation
languages, the first described as high-level languages, use vocabulary related to the problem being solved. For example,
COBOL (Common Business Oriented Language) uses terms like file, move and copy.
FORTRAN (FORmula TRANslation) and ALGOL (ALGOrithmic Language) were developed
mainly for scientific and engineering problems, although one of the ideas behind the
development of ALGOL was that it was an appropriate language to define algorithms. BASIC
(Beginners All purpose Symbolic Instruction Code) was developed to enable more people to
write programs. All these languages follow the procedural paradigm. That is, they describe,
step by step, exactly the procedure that should be followed to solve a problem.
The problem with procedural languages is that it can be difficult to reuse code and to modify
solutions when better methods of solution are developed. In order to address these
problems, object-oriented languages (like Eiffel, Smalltalk and Java) were developed. In
these languages data, and methods of manipulating the data, are kept as a single unit called
an object. The only way that a user can access the data is via the object's methods. This
means that, once an object is fully working, it cannot be corrupted by the user. It also
means that the internal workings of an object may be changed without affecting any code
that uses the object.
A further advance was made when declarative programming paradigms were developed. In
these languages the computer is told what the problem is, not how to solve the problem.
Given a database or a set of rules, the computer searches for a solution. In declarative programs,
the computer is not given a procedure to follow. Instead, the desired results are described directly.
One example is XAML (pronounced zammel ['zæm??]), a declarative language used to describe user interfaces in Silverlight and WPF.
Another recent programming paradigm is functional programming. Programs written using this
paradigm use functions, which may call other functions (including themselves). These
functions have inputs and outputs. Variables, as used in procedural languages, are not used
in functional languages. Functional languages make a great deal of use of recursion.
See also
External links
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