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Languages and Extensions



Now we will examine the relationship between languages and extensions. Traditionally, the term language refers (in the computer world) to some form of computer language, a set of common instructions that when properly assembled, create a program or application. Most users are well aware of at least one computer language: BASIC, Pascal, FORTRAN, C, and so on. Such languages are traditionally understood to be real languages because one can cab construct a program with them that can thereafter run generally without need of external support from an interpreter.

Today, the climate is different. For example, the popularity of shell languages, which are used primarily on the UNIX platform, has greatly increased. They are written in a syntax that meets the requirements of the shell or command interpreter of the given platform. These languages cannot create entirely standalone programs that execute without a command interpreter, yet these languages have become vastly popular. A programmer who can proficiently program is such a language is almost guaranteed to land a job somewhere.

As such, these languages stretch the definition of language itself. For even these programs cannot run without assistance from the underlying system, they are indeed full-fledged programs that can and often do run various services and functions of the Internet.

Similarly, there are interpreted languages such as Perl that offer extreme power to the user. They can often interface not just with their own interpreter, but with various shell languages and system calls. They can even be nested within other language constructs. A typical example would be a Perl script nested within a TCL script or within a C program. These are languages that cross the barriers (or perhaps bridge the gaps) between one or more real languages.

Hypertext Markup Language (HTML) is a language, but it should be interpreted by a hypertext reader (Navigator, Internet Explorer, Grail, Arena, Lynx, Opera, Powerbrowser, Netcruiser, and so forth). JavaScript and VBScript are languages that stand between Perl and HTML. But they perform only a limited set of tasks. In order to create a fully functional and dynamic Web-page environment, one must use a combination of languages. So we can call a language any set of instructions that can perform more than simple display processes, dynamically and without user intervention (that is, any set of instructions that could potentially automate a task).

In contrast, an extension is any set of instructions, declarations, or statements that formulate one application of a particular language. Most commonly, the term extension refers to HTML extensions. For example, tables in HTML are extensions. They are statements that alter the face of a Web page. The use of tables is becoming more common because tables provide control of the Web page’s appearance. Perhaps the easiest way to grasp the concept of extensions is to understand that they are statements that extend the originally intended implementation of HTML.





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