This article by Covalent Technologies engineer and Apache
Software Foundation member, William Rowe, Jr., outlines three major changes made to Apache that affect the platforms other
than Unix, such as Multiple Process Modules, the Apache Portability Runtime library,
"This article outlines three major changes made to Apache that affect the 'fringes' (i.e., those platforms other
than Unix), especially as they relate to the Windows platform. The first is a split between the server and the
request processing logic into a Multiple Process Module, or MPM. The second change is the breaking out of
platform-specific code into the Apache Portability Runtime library, or APR. The third, and biggest,
Windows-NT-specific change is the introduction of Unicode, or utf-8 encoded filenames."