STRUCTURED QUERY LANGUAGE

Structured Query Language (SQL), in computer science, a database sublanguage used in querying, updating, and managing relational databases. Derived from an IBM research project that created Structured English Query Language (SEQUEL) in the 1970s, SQL is an accepted standard in database products. Although it is not a programming language in the same sense as C or Pascal, SQL can either be used in formulating interactive queries or be embedded in an application as instructions for handling data. The SQL standard also contains components for defining, altering, controlling, and securing data. SQL is designed for both technical and nontechnical users.

HYPERTEXT MARKUP LANGUAGE (HTML)

Hypertext Markup Language (HTML) in computer science, the standard text-formatting language since 1989 for documents on the interconnected computing network known as the World Wide Web. HTML documents are text files that contain two parts: content that is meant to be rendered on a computer screen; and markup or tags, encoded information that directs the text format on the screen and is generally hidden from the user. HTML is a subset of a broader language called Standard Generalized Markup Language (SGML), which is a system for encoding and formatting documents, whether for output to a computer screen or to paper.

Some tags in an HTML document determine the way certain text, such as titles, will be formatted. Other tags cue the computer to respond to the user's actions on the keyboard or mouse. For instance, the user might click on an icon (a picture that represents a specific command), and that action might call another piece of software to display a graphic, play a recording, or run a short movie. Another important tag is a link, which may contain the Uniform Resource Locator (URL) of another document. The URL can be compared to an address where a particular document resides. The document may be stored on the same computer as the parent document or on any computer connected to the World Wide Web. The user can navigate from document to document simply by clicking on these links. HTML also includes markups for forms, that let the user fill out information and electronically send, or e-mail, the data to the document author, initiate sophisticated searches of information on the Internet, or order goods and services.

The software that permits the user to navigate the World Wide Web and view HTML-encoded documents is called a browser. It interprets the HTML tags in a document and formats the content for screen display. Since HTML is an accepted standard, anyone can build a browser without concerning themselves with what form various documents will assume, unlike documents produced by typical word processors, which must be translated into a different format if another word processing application is used. Most sites on the World Wide Web adhere to HTML standards and, because HTML is easy to use, the World Wide Web has grown rapidly. HTML continues to evolve, however, so browsers must be upgraded regularly to meet the revised standards.

Date: 2015-02-16; view: 910