Saturday 14 April 2012

Programming paradigm


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 (assignment, evaluation, continuations, data flows, etc.).


A multi-paradigm programming language is a programming language that supports more than one programming paradigm. As Leda designer Timothy Budd puts it: "The idea of a multiparadigm language is to provide a framework in which programmers can work in a variety of styles, freely intermixing constructs from different paradigms." The design goal of such languages is to allow programmers to use the best tool for a job, admitting that no one paradigm solves all problems in the easiest or most efficient way.
An example is Oz, which has subsets that are logic (Oz descends from logic programming), a functional, an object-oriented, a dataflow concurrent, and other language paradigms. Oz was designed over a ten-year period to combine in a harmonious way concepts that are traditionally associated with different programming paradigms. A programming paradigm provides for the programmer the means and structure for the execution of a program.


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 symbolic labels. Assembly language programming is considered a low-level paradigm although it is a 'second generation' paradigm. Even assembly languages of the 1960s actually supported library COPY and quite sophisticated conditional macro generation and pre-processing capabilities. They also supported modular programming features such as CALL (subroutines), external variables and common sections (globals), enabling significant code re-use and isolation from hardware specifics via use of logical operators as READ/WRITE/GET/PUT. Assembly was, and still is, used for time critical systems and frequently in embedded systems.
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,
C - developed circa 1970 at Bell Labs
COBOL (Common Business Oriented Language) - uses terms like file, move and copy.


FORTRAN (FORmula TRANslation) - using mathematical language terminology, it was developed mainly for scientific and engineering problems.
ALGOL (ALGOrithmic Language) - focused on being an appropriate language to define algorithms, while using mathematical language terminology and targeting scientific and engineering problems just like FORTRAN.
PL/I (Programming Language One) - a hybrid commercial/scientific general purpose language supporting pointers.
BASIC (Beginners All purpose Symbolic Instruction Code) - was developed to enable more people to write programs.

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