Any developer who wants to create multitier applications using the Microsoft Windows platform as the foundation must rely on many separate pieces of software. Some of these pieces will be supplied by Microsoft, and you or your company will write other pieces. Still other pieces can come from third-party software vendors.

The Component Object Model (COM) is the primary glue that binds all these pieces of software together. It enables programmers and companies to distribute and reuse their code efficiently. COM+, an extended version of COM, provides a valuable runtime environment for components that run in the middle tier. COM+ and a handful of other critical Windows services, such as Internet Information Services (IIS), Active Server Pages (ASP), and Microsoft Message Queuing (MSMQ), provide the building blocks that enable programmers and companies to create large-scale multitier applications.