Changes

The meaning or [[semantics]] of any particular construct in a programming language is most commonly described in fairly precise English.  Several unsuccessful attempts have been made to find a useful and formal way of describing the semantics.

The meaning or [[semantics]] of any particular construct in a programming language is most commonly described in fairly precise English.  Several unsuccessful attempts have been made to find a useful and formal way of describing the semantics.

The more important programming languages have an internationally-agreed official standard (ISO is the international standards organisation, ANSI is the standards body in the United States). In theory, programs which conform to the relevant standard should be usable on most types of computer; this works in practice most of the time, provided that the programmers have been careful to avoid machine dependencies. Such agreed standards are usually revised every 5 to 15 years, often with new features being added, and sometimes with old features being either removed or marked as obsolete.

The more important programming languages have an internationally agreed official standard (ISO is the international standards organisation, ANSI is the standards body in the United States). In theory, programs which conform to the relevant standard should be usable on most types of computer; this works in practice most of the time, provided that the programmers have been careful to avoid machine dependencies. Such agreed standards are usually revised every 5 to 15 years, often with new features being added, and sometimes with old features being either removed or marked as obsolete.

Very few programmers learn a programming language directly from the formal definition, which exists primarily as a reference which can be consulted in cases of doubt.  There are usually plenty of books and training courses for the more common programming languages.

Very few programmers learn a programming language directly from the formal definition, which exists primarily as a reference which can be consulted in cases of doubt.  There are usually plenty of books and training courses for the more common programming languages.

:LISP for list processing and artificial intelligence.

:LISP for list processing and artificial intelligence.

Successful programming languages evolve over time to become more general-purpose, or form the basis for other languages (e.g. '''C''' -> '''C++'''). The evolution often involves incorporating good features from other languages. The general trend is for languages to become more general-purpose and provide more levels of abstraction. The concepts of structured programming were put on a sound theoretical basis in the early 1970's and these have also influenced the evolution of some programming languages (e.g. Fortran 66 -> Fortran 77). The idea of objects (combining data with the applicable operations) was available in Simula in the mid 1960's, but did not become popular until the advent of C++ in the early 1980's and Java in the mid 1990's; confusingly, Java and C++ have a lot of syntax in common, but the meaning (semantics) may differ drastically for what looks the same when written down.

Successful programming languages evolve over time to become more general-purpose, or form the basis for other languages (e.g. '''C''' -> '''C++'''). The evolution often involves incorporating good features from other languages. The general trend is for languages to become more general-purpose and provide more levels of abstraction. The concepts of structured programming were put on a sound theoretical basis in the early 1970s and these have also influenced the evolution of some programming languages (e.g. Fortran 66 -> Fortran 77). The idea of objects (combining data with the applicable operations) was available in Simula in the mid 1960s, but did not become popular until the advent of C++ in the early 1980s and Java in the mid 1990s; confusingly, Java and C++ have a lot of syntax in common, but the meaning (semantics) may differ drastically for what looks the same when written down.

====Declarative programming====

====Declarative programming====