applet

applet A program, written in JAVA, that can be embedded in a WEB PAGE using special TAGS. When a BROWSER links to that page, the page, along with the applet, is transferred to the computer on which the browser resides. The applet starts executing when the area in which it resides on the page comes within the browser window. Applets can carry out a diverse number of functions. For example, they are used for ANIMATIONS, for FORMS processing, and for access to remote databases. One of the potential problems with applets is that they are programs transferred to a computer from the SERVER containing the Web page in which they are embedded. This means that applets could, theoretically, provide a means whereby VIRUSes could be spread from one computer to another. In order to prevent this, the original designers of the applet mechanism have severely limited the actions which an applet can carry out; for example, they are not allowed to read from or write to a file, in effect using a SANDBOX. In later versions of the language DIGITAL SIGNATURES are used as a mechanism for preventing destructive access to a computer. When applets first appeared they revolutionized the development of WEB PAGES: until then such pages had consisted of text, some very primitive animations, and some forms processing which was carried out by the server on which a Web page resided, rather than the client. Since applets have appeared, a large number of other technologies have emerged which achieve much of what was intended by applets, for example ACTIVE X and SCRIPTING LANGUAGES. See also JAVA APPLET RATING SERVICE.