Microsoft Windows NT Workstation 4.0 is one of the most powerful 32-bit operating systems available for business computing today. It offers the ease of use of Windows 95 along with higher performance, greater reliability, and better security.

One of the most remarkable aspects of Windows NT's architecture is that portions of the operating system--the subsystems--run in user-mode processes alongside application processes. The subsystems provide the environments in which applications run. The Win32 subsystem provides the application program interface (API) services that Win32 applications call to do useful things such as create windows and open files. Applications and subsystems enjoy a client/server relationship in which the applications are the clients and the subsystems are the servers. One of the benefits of this architecture is that you can include support for other types of applications (such as Unix applications) to Windows NT simply by adding subsystems.

Much of Windows NT's renowned stability is a direct result of the operating system's architecture. Applications can't interfere with one another because they run in separate address spaces. Operating system code and data in the subsystems is protected from applications because subsystems, too, reside in their own address spaces. The Windows NT Executive shares address space with running processes, but it's protected by the wall between kernel mode and user mode. It's impossible for an application to corrupt code or data stored in the Windows NT Executive because the processor notifies the operating system of or prevents invalid memory accesses before they occur.

Ultimately, an operating system's reliability and resistance to application-induced crashes is a function of how effectively it guards itself and the processes it hosts from other processes. Windows NT excels in this regard because of the high level of protection it provides both to the operating system and to its application programs.

Using the NT File System (NTFS) is faster and much less prone to damage than the out-of-date File Allocation Table (FAT) used by DOS and Windows 3.x. The NTFS allows heavy-duty security to protect sensitive files from unauthorized access; is able to turn multiple hard drives into high-performance, fault-tolerant disk arrays without special hardware; and uses a superior compression scheme that lets you choose which drives, folders, and even individual files you want to compress.

Windows NT Workstation 4.0 isn't for everybody. It isn't 100-percent compatible with all the software you can run under Windows 3.1 or Windows 95, and it's a lot fussier about hardware. Laptop users and heavy gamers are particularly likely to find NT Workstation 4.0 unsuitable. The cost of NT Workstation 4.0 is $319, which is an attractive proposal for some people who want a faster or more stable environment than Windows 95.