| Windows 32-Bit API
Developers and end-users have made enormous investments in Windows programming and Windows applications. Most of these applications have been developed to run on both the 16-bit 80286 processor and the 32-bit 80386 and 80486 systems. Although highly capable, programs written to the Windows 16-Bit API, which is supported by Windows 3.0, are constrained by the memory limits inherent in a 16-bit architecture. Code must be divided into segments which cannot exceed 64K (65,536 bytes). This makes programming more difficult. It also imposes a performance penalty on high-performance 80486 and RISC-based systems.
The success of Windows Version 3.0, made it clear that an easy migration path from existing 16-bit Windows applications to a 32-bit programming interface was required. Unfortunately, OS/2 Presentation ManagerTM (PM) was not an appropriate path. Although similar in appearance from an end-user perspective, the programming details of Windows and PM are completely different. So different in fact that most software developers found it necessary to completely rewrite their application when going from Windows to Presentation Manager. This is a major reason why there are so few OS/2 PM applications available.
The Windows 32-Bit API (Windows 32) has been designed to make the transition from the Windows 16-Bit API (Windows 16) to 32-bit as easy as possible. Only minimal changes have been made to the syntax of the Windows 32 API. The API names are the same as Windows 16. The semantics are identical. The message order is identical. In fact, it is possible to keep a single source code base and compile that source code into both 16-bit and 32-bit programs (see Figure 4).
While the Windows 32 API is extremely compatible with the Windows-16 API, it also contains significant new features. These features include preemptive multitasked processes that use separate address spaces, preemptive threads, semaphores, shared memory, named pipes, mailslots, and memory mapped file I/O. GDI (Graphics Device Interface) improvements include Bézier curves, paths, transforms, and a device-independent color model.
The Windows 32-Bit API is fully supported in both Windows Enhanced-mode and Windows NT-mode. The Windows 32-Bit API will first be available in the Windows NT product during 1992. It will be added to Windows Enhanced-mode in late 1992 or early 1993. Programs written to the Windows 32-Bit API will run binary compatibly on both Windows NT-mode and Windows Enhanced-mode. All Windows 32 features are supported by both Windows Enhanced-mode and Windows NT-mode, including preemptive multitasking. Windows 32 programs will be fully source compatible between x86 and MIPS processors. Software Developer Kits for the Windows 32-Bit API will be available in late 1991.
The following highlights some key features of the Windows 32-Bit API.
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