Code on demand

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In computing, code on demand is a general term for any technology that sends executable software programs from a server computer to a client computer upon request from the client's software (e.g., browser).

Code on demand is a specific use of mobile code. A well-known example for the code on demand paradigm are Java applets: An applet's program code lies inactive on some web server until a user (client) requests a web page that contains a link to the applet using his web browser. Upon this request, the web page and the applet are transported to the user's machine using HTTP. When the page is displayed, the applet is started in the browser and executes locally, inside the user's computer until it is stopped (e.g. by the user leaving the applet's web page). This completes the applet's life cycle.

Note that in most cases, the user is not aware that the Web page is downloaded and is executing mobile code into his/her workstation. The user does not "explicitly" or "intentionally" request the mobile code; nor does the user explicitly or intentionally terminate the mobile code.