||This article may contain original research. (June 2009)|
In computing, an applet is any small application that performs one specific task that runs within the scope of a larger program, often as a plug-in. An applet typically also refers to Java applets, i.e., programs written in the Java programming language that are included in a web page. The word Applet was first used in 1990 in PC Magazine.
Applet as a standalone application 
Provided that an applet is hosted by an operating system, it can function as any other normal software application but performs only a small set of tasks. Examples of applications often classified as applets are all of the accessories bundled in Microsoft Windows (such as Windows Notepad or Microsoft Paint). Applets are not full-featured application programs, and are intended to be easily accessible.
Applet as an extension of other software 
In some cases, an applet does not run independently. These applets must run either in a container provided by a host program, through a plugin, or a variety of other applications including mobile devices that support the applet programming model.
Web-based Applets 
Applets are used to provide interactive features to web applications that cannot be provided by HTML alone. They can capture mouse input and also have controls like buttons or check boxes. In response to the user action an applet can change the provided graphic content. This makes applets well suitable for demonstration, visualization, and teaching. There are online applet collections for studying various subjects, from physics to heart physiology. Applets are also used to create online game collections that allow players to compete against live opponents in real-time.
An applet can also be a text area only, providing, for instance, a cross platform command-line interface to some remote system. If needed, an applet can leave the dedicated area and run as a separate window. However, applets have very little control over web page content outside the applet dedicated area, so they are less useful for improving the site appearance in general (while applets like news tickers or WYSIWYG editors are also known). Applets can also play media in formats that are not natively supported by the browser
HTML pages may embed parameters that are passed to the applet. Hence the same applet may appear differently depending on the parameters that were passed.
Examples of Web-based Applets include:
- QuickTime movies
- Flash movies
- Windows Media Player applets, used to display embedded video files in Internet Explorer (and other browsers that support the plugin)
- 3D modeling display applets, used to rotate and zoom a model
- Browser games can be applet-based, though some may develop into fully functional applications that require installation.
Applet vs. Subroutine 
A larger application distinguishes its applets through several features:
- Applets execute only on the "client" platform environment of a system, as contrasted from "servlet". As such, an applet provides functionality or performance beyond the default capabilities of its container (the browser).
- The container restricts applets' capabilities.
- Applets are written in a language different from the scripting or HTML language that invokes it. The applet is written in a compiled language, whereas the scripting language of the container is an interpreted language, hence the greater performance or functionality of the applet. Unlike a "subroutine", a complete web component can be implemented as an applet.
Java Applet 
Java Applets can provide web applications with interactive features that cannot be provided by HTML. Since Java's bytecode is platform-independent, Java applets can be executed by browsers running under many platforms, including Windows, Unix, Mac OS, and Linux. When a Java technology-enabled web browser processes a page that contains an applet, the applet's code is transferred to the client's system and executed by the browser's Java Virtual Machine (JVM). An HTML page references an applet either via the deprecated <APPLET> tag or via its replacement, the <OBJECT> tag.
Recent developments in the coding of applications including mobile and embedded systems have led to the awareness of the security of applets.
Open Platform Applets 
Applets in an open platform environment should provide secure interactions between different applications. A compositional approach can be used to provide security for open platform applets. Advanced compositional verification methods have been developed for secure applet interactions.
Java Applets 
Web-based Applets 
In an applet-enabled web browser, many methods can be used to provide applet security for malicious applets. A malicious applet can infect a computer system in many ways, including denial of service, invasion of privacy, and annoyance. A typical solution for malicious applets is to make the web browser to monitor applets' activities. This will result in a web browser that will enable the manual or automatic stopping of malicious applets. To illustrate this method, AppletGuard was used to observe and control any applet in a browser successfully.
See also 
- "AskOxford: applet", Oxford Dictionaries. Accessed on July 21, 2009
- "applet: Definition from Answers.com", Answers.com. Accessed on July 21, 2009
- "Oxford English Dictionary". 2011. Archived from the original on 20 July 2011. Retrieved 2011-08-23.
- Paul Falstad online applet portal
- The virtual hearth
- ObjectPlanet.com, an applet that works as news ticker
- Sferyx.com, a company that produces applets acting as WYSWYG editor.
- Cortado applet to play ogg format
- "Applets", Sun Developer Network. Accessed on July 21, 2009
- "HTML applet tag", W3Schools. Access on July 21, 2009
- Barthe, Gilles; Gurov, Dilian; Huisman, Marieke (2002). "Compositional Verification of Secure Applet Interactions". CiteSeerX: 10.1.1.16.1254. Retrieved 2010-04-10.
- Hassler, Vesna; Then, Oliver (1998). "Controlling Applets' Behavior in a Browser". Retrieved 2010-04-10.
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