script language

Script languages are programming languages whose basic aim is to realize mostly only small applications or sequences of instructions. The code sequences - which are often also referred to as scripts - have certain specific characteristics. One of these features is that scripts are often not translated into machine-readable code by a compiler, but are executed at runtime by an interpreter. Script languages are often also assigned specific tasks, so that their syntax is easy to keep track of.

The further significant characteristics of script languages are:

• the built-in memory management, the garbage collection,
• automatically declared variables,
• dynamic class membership or proto-type based inheritance and
• missing differentiation of types (Typlos).

The interpretable Sciptsprachen have a clear speed disadvantage opposite programs in compiled programming languages with computation-intensive tasks. Special methodologies in the handling of script languages try to circumvent this disadvantage. These include the interpretation by a virtual machine, the possible inclusion of in low- level programming languages, such as the time-critical code sequences written in programming language C etc., or a runtime optimizing as well as the translation into bytecode.

Script languages and their interfaces

Originally the script languages realized only interactive interfaces for the input of commands to the respective operating system. By the further addition of variables and expressions as well as control structures to the script languages independent code sequences - scripts or smaller programs - can develop, which automate the expirations of a system. These are called shell scripts under UNIX and batch files under the Disk Operating System( DOS) and Windows.

Another segment of script languages is their use in terms of adding functionality to an application program. In this way, command sequences in simple text files that can be used flexibly may result in completely modified functions. Examples of this type of script languages are: Visual Basic for Applications( VBA) for use in Microsoft programs and Emacs-Lisp as the script language of the editor Emacs.

An additional group defines those script languages, which can be regarded as independent - interpretative - programming languages. These allow the use of different programming paradigms and support the concepts necessary for independent software realizations. Examples of this type of script languages are:

Ruby, an object-oriented scripting language

PHP, Hypertext Preprocessor, for the development of web applications

JavaScript, for dynamic web applications

Python, an object-oriented scripting language

Perl, for editing texts

REXX, a scripting language from IBM

LISP, for processing lists

Even in this group, however, there are still specializations. For example, the text processor awk used under UNIX or the script language GLE for generating graphics.

Script languages are also frequently used in the WWW, where they are primarily used for dynamic aspects or the realization of entire web applications on both the server and client sides. The processing of script languages always takes place in the form of text files, so that a high flexibility is given. Also by the high spreading degree today the script languages often represent application areas, which were reserved originally for the conventional programming languages.