What's ActiveX? This Time with Feeling
Since the release of ActiveX controls, we have been trying to establish the "exact" difference between an OLE Control (OCX) and an ActiveX control; at a glance, the difference "seems" trivial.
Talking to Microsoft South Africa, we receive varied responses. Product Management's response was that most probably Microsoft wants to get away from the OLE terminology, and hence an ActiveX is simply an OCX with a different coat. Development/support staff refers to an ActiveX as an OCX designed for the Internet—however, they are basically the same.
Colleagues in the non-Microsoft development world refer to ActiveX controls as "lightweight" OCX controls, without the unnecessary gumppff, such as Online Help.
Can you possibly resolve this seemingly "minor" dispute?
Best regards,
Willy-Peter Schaub
Dr. GUI has been confused about ActiveX, too. Here's what he's learned about ActiveX controls:
The specification for ActiveX controls has been relaxed to give developers the ability to create smaller, faster controls that are more suitable for the Internet. In the new OLE control specification, we make use of component categories, which allows the relaxing of some previous rules identifying interfaces as being mandatory and allows greater flexibility to efficiently target certain areas of functionality without having to provide superfluous support to qualify as a control. We also added some new features like windowless objects, URL monikers, asynchronous monikers, progressive downloading, and OLE Hyperlinks. (And, perhaps most importantly, we support marking controls as safe for data download and safe for scripting.)
Keep in mind that an ActiveX control is just another term for an "OLE Object" or "COM Object." A "COM Object" is required to support the IUnknown interface. In addition, all ActiveX controls must be self-registering (that is, they must implement and export DllRegisterServer and DllUnregisterServer). Since IUnknown doesn't allow you to do much, you want to implement at least one additional interface. However, these minimal requirements allow controls to be as lightweight as possible.
For a description of the ActiveX technologies, see http://www.microsoft.com/kb/peropsys/win95/q154544.htm on the Microsoft Web site. To learn more about URL monikers, asynchronous monikers, progressive downloading, and OLE Hyperlinks, see http://www.microsoft.com/intdev/prog-gen/moniker.htm#url.