I understand that COM is really a way to program (i.e. like structured programming, or OO programming). However it is a little old. So I was just wondering what has really replaced this set of specifications? Will I find this in .NET documentation?
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1In many ways COM is more of a specification about how data is transferred between threads and programs. It has the effect of creating a programming style but at it's core it's about data transfer. – JaredPar Mar 05 '12 at 19:42
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COM has not been replaced. The Component Object Model is a core part of Windows and will remain so for the foreseeable future.
COM provides you with one mechanism of inter process communication (communicating between applications on a machine), it is also used as a much simpler (for the consumer) system of sharing dlls. Its COM (or ActiveX, or OLE - all the same) that enables VBA to work so well in MS Office, it is the foundation of ActiveX controls.
COM is not a way to program (unlike OOP etc) it is a technology that works on windows to make access to other applications during runtime easier.
.NET can use COM object with wrappers, and if you want to allow any app to access your functionality, its still best to provide a COM wrapper.
Other methods of inter app coms now exist such as ZeroMQ.
Toby Allen
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The original specification for COM is old in age, but the specification as well as the concepts are still in use, and you can still create and consume COM objects.
For .NET, you can start by looking at the following links:
Com Interop Part 1: C# Client Tutorial (C#) @ MSDN
Interoperating with unmanaged code @ MSDN
In addition, there are other specs that are very similar to COM or have semantics that are the same. Most notably, XPCOM is in use in FireFox for their plugin spec and also used internally to FireFox to connectable objects.
WinRT is an upcoming platform update for windows that is also heavy in COM concepts.
There are some useful here: Why is WinRT unmanaged @ StackOverflow
For .NET developers, a lot of the declarative overhead is hidden as mentioned here: WinRT demystified - Miguel de Icaza
The head of the spec is here: The Windows Runtime @ MSDN
And in the context of COM, developing WinRT components with C++ has similarities, although some syntax is borrowed from managed C++: Creating Windows Runtime Components in C++ @ MSDN
