Active-X is an interprogram usage/communication technology from Microsoft. In Microsoft usage Active-X includes previous technologies such as Dynamic Data Exchange (DDE), Object Linking and Embedding (OLE) and the Common Object Module (COM). In general usage, Active-X is the incremental technology added to COM that extends interprogram communication to web sites.

ActiveX is subdivided into two subsets -- ActiveX Controls and ActiveX Documents. Controls and Documents differ in that documents automatically merge the full applications menu from the embedded control into the existing menu of the using application whereas controls are stand alone entities. ActiveX can also deal with both Server and Client side components. Client Side components run on the target machine much like Javascript and are pretty much limited to clients running Internet Explorer. Server Side components run on the Server and can be used by any browser. They are typically found as part of Active Server Pages (ASPs)

Active-X is often used to implement "controls" -- programs that do things. In this context, it is similar in usage (if not internal construction) to Javascript or VBscript. In effect, client side Active-X is a Windows program that can be downloaded and executed from a web page without necessitating explicit user download, install, and execute steps. This is very useful for providing capabilities that are not included in standard web languages. Unfortunately, it can also -- in concept -- be used to embed malicious programs into web pages that will eventually be run on a viewer's PC. Microsoft provides some authentication capability for Active X control downloading. Opinions differ on whether the protections are adequate. The protections are packaged with other capabilities. For example in Internet Explorer 5, allowing "cookies" (required by many sites for full capability) also allows digitally signed Active-X controls to run.

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