Component Services (COM and DCOM)

  • Article

The Component Object Model (COM) is a platform-independent, object-oriented system for creating binary software components that can interact with other COM-based components in the same process space, in other processes, or on remote devices.

Microsoft Windows® CE .NET offers the following levels of run-time support for COM-based applications:

  • A minimal COM provides a baseline application programming interface (API) set for COM object creation. This feature requires about 10–20K of memory.
  • COM provides a midrange implementation of COM and OLE automation that supports only in-process free-threaded objects. This feature requires about 100-200K of memory.
  • DCOM provides a full-featured COM implementation including services on a remote device and requires over 700K of memory. By default, the remoting capability is disabled, which provides a more secure environment for the device. This enables the DCOM's local server capabilities and still allows the device to be connected to the Internet. To enable the remoting capability, set the Sysgen variable, SYSGEN_DCOM_REMOTEACCESS, to 1.
  • COM Storage adds structured storage functionality to Minimal COM, COM, or DCOM implementations.

The topics in this section describe the programming model for COM and DCOM on Windows CE and provide guidelines for the implementation of interfaces, management of memory, and configuration of registry settings. The documentation targets the differences between the implementations of COM on Windows CE and on Microsoft Windows NT®, and is not intended to be a comprehensive guide to COM programming. Familiarity with the COM objects and interfaces, type libraries, and essential distributed programming concepts is assumed. Background and conceptual information are available through the following resources:

  • For information about component development, see this Microsoft Web site.
  • For information about Windows CE, see this Microsoft Web site.
  • Inside COM, by Dale Rogerson, Microsoft Press® Books, 1996, and Inside Distributed COM, by Guy and Henry Eddon, Microsoft Press Books, 1998. For information about these titles and other COM developer guides, see this Microsoft Web site.

Unless it is specified otherwise, the term COM in this documentation refers to features that are available in the midrange Windows CE implementation, and DCOM refers to the features that are provided in the full-featured implementation. Note that this usage varies somewhat from the desktop documentation, in which a single programming model covers all of the COM services, whether they are in-process, local, or remote.

Finally, independent software vendors (ISVs) should note that not all Windows CE device platforms include COM run-time support. To verify that a particular Windows CE device platform provides the level of COM support that your application requires, consult the OEM of your target device.

The following topics show the supported APIs for each feature:

Last updated on Wednesday, April 13, 2005

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