Windows Architecture & The Windows Programming Model

Windows Architecture

Windows was originally a shell built onto MS-DOS which gradually took on the character of a real operating system. Windows 3.1 only used the underlying MS-DOS code for file I/O, Windows 95 integrates the 'MS-DOS' code into Windows itself, and Windows NT is an entirely new operating system altogether, borrowing some interface ideas from Win16 to be sure, but borrowing even more from UNIX and VMS and re-asserting the original Windows idea: a platform independent system.

The Win32 core is made up of three key modules: Kernel32, User32, and GDI32. These modules take care of our Win32 platform and communicate with one another. It is this core that receives the Windows API calls from the Windows application as well. These modules interface with the rest of the system to run the computer hardware and manage file I/O (Shell32, the basis of the Windows 95 and Windows NT 4.0 shells, might also be mentioned).

Kernel32 takes care of task scheduling, message administration, memory management, and the like. User32 runs the application windows, their menus, dialog boxes - the core logic of the Windows infrastructure. GDI32 takes care of graphical operations (even text operations - at least most of them) and has its own API for performing rather advanced graphical operations in a totally device independent way. Dynamic Link Libraries (DLLs) are a cornerstone of Windows architecture as well. A dynamic link library is a function library that lives an independent life on disk and is linked into the application that wants to call its functions at run-time.

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