The Component Object Model, COM for short, is a widely used platform that allows different pieces of software to interoperate without needing to know what language or programming environment has been used for implementing any of them. It has been the de facto standard for application interoperability for quite some time. The technology was invented in 1993 and started gaining popularity in 1997. Today, it is practically everywhere. COM is so popular because it makes exposing automation interfaces or extensibility points very easy. Some programs, such as Microsoft Office, use it to expose object models that can be exploited by script authors. Other programs, such as Internet Explorer and Windows Media Player, expose pieces of user interface along those object models, so those can be embedded into other programs and even web pages. COM has been extended with the DCOM system to provide distributed communication and allow objects to be deployed to remote machines. DCOM eliminates the need to know if an object runs on the same machine or not and makes it very easy to build distributed systems. For example, the WMI infrastructure that we will be discussing in the next chapter uses DCOM as its intermachine communication medium.
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