Like Windows 95 and Windows 98, but unlike earlier versions of Windows, Windows NT is its own operating system and does not rely on the underlying presence of the 16-bit DOS operating system. Unlike Windows 95 and Windows 98, NT 3.1, 3.51, and now 4.0 are all true 32-bit operating systems. Windows 95 and Windows 98, unfortunately, are still hybrids relying on both 16-bit and 32-bit core code.
Sometimes, an application will perform on one system but not on the other because the developers have made use of some tricks that are possible under one operating system but not in the other. In many ways, Windows 98 is still a DOS-based operating system because, even though it is not visible on the surface, extensive support is still provided to ensure that the older DOS and Windows 3.x applications will function under Windows 98. Windows NT, however, avoids the limitations and problems inherent in this schizophrenic approach by simply not supporting the earlier system services.
In other cases, applications may not run on both systems because they have been written to depend on advanced operating system-specific features. For example Windows NT supports some features, such as networking APIs, that are not supported under other operating systems. (See Chapter 22 for information about adding network support to your applications.)
Another difference that can affect your applications is how security and access permissions are used in Windows NT. These permissions are not supported under Windows 98. (See Chapter 20 for details on the Win32 security and cryptography APIs.)
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The Win32 driver model allows developers to create a single hardware driver that will function on both the Windows 98 and Windows NT (5.0) operating systems. Previously, developers were required to write separate and independent drivers for each operating system, making it difficult for both developers and users to upgrade hardware.