of shipping a year later than Windows 95, by default there is no Legacy Plug and Play support and no Device Manager on Windows NT 4.0, which greatly simplifies installation of hardware devices (although limited support could be installed later). Many basic DOS programs would run; however, graphical DOS programs would not run because of the way they accessed graphics hardware. Although Windows NT 4.0 introduced an application programming interface (API) for defragmentation, there was no built-in defragmentation utility, unlike Windows 95. Also, Windows NT 4.0 lacked USB support, a preliminary version of which would be added to OEM editions of Windows 95 in OSR 2.1. The difference between the NT family and 9x family would remain until the release of Windows XP in 2001. At that time, the APIs — such as OpenGL and DirectX — had matured sufficiently to be more efficient to write for common PC hardware, and the hardware itself had become powerful enough to handle the API processing overhead. The maximum amount of supported physical random-access memory (RAM) in Windows NT 4.0 is 4 GB, which is the maximum possible for a 32-bit operating system that does not support PAE. By comparison, Windows 95 fails to boot on computers with more than approximately 480 MB of memory. Like previous versions of NT, version 4.0 can run on multiple processor architectures. Windows 95, however, can only run on x86. Editions Windows NT 4.0 Server was included in versions 4.0 and 4.5 of BackOffice Small Business Server suite. Client Windows NT 4.0 Workstation was designed for use as the general business desktop operating system. Servers Windows NT 4.0 Server, released in 1996, was designed for small-scale business server systems. Windows NT 4.0 Server, Enterprise Edition, released in 1997, is the precursor to the Enterprise line of the Windows server family (Advanced Server in Windows 2000). Enterprise Server was designed for high-demand, high-traffic networks. Windows NT 4.0 Server, Enterprise Edition includes Service Pack 3. The Enterprise Edition saw the introduction of the boot flag, which changed the default virtual address space mapping from 2 GB kernel and 2 GB user space to 1 GB kernel and 3 GB userland. This version also sees the first introduction of cluster service. Windows NT 4.0 Terminal Server Edition, released in 1998, allows the users to log on remotely. The same functionality was called Terminal Services in Windows 2000 and later server