1.3 Microsoft Windows and Windows-specific extensions
This API is intended to be usable within all implementations and versions of Microsoft Windows from Microsoft Windows Version 3.0 onwards. It thus provides for Windows Sockets implementations and Windows Sockets applications in both 16 and 32 bit operating environments.
Windows Sockets makes provisions for multithreaded Windows processes. A process contains one or more threads of execution. In the Windows 3.1 non-multithreaded world, a task corresponds to a process with a single thread. All references to threads in this document refer to actual "threads" in multithreaded Windows environments. In non multithreaded environments (such as Windows 3.0), use of the term thread refers to a Windows process.
The Microsoft Windows extensions included in Windows Sockets are provided to allow application developers to create software which conforms to the Windows programming model. It is expected that this will facilitate the creation of robust and high-performance applications, and will improve the cooperative multitasking of applications within non-preemptive versions of Windows. With the exception of WSAStartup() and WSACleanup() their use is not mandatory.