The wiki on Windows NT also summarizes this, with links to Zachary. "Microsoft hired a group of developers from Digital Equipment Corporation led by Dave Cutle

The wiki on Windows NT also summarizes this, with links to Zachary. "Microsoft hired a group of developers from Digital Equipment Corporation led by Dave Cutler to build Windows NT, and many elements of the design reflect earlier DEC experience with Cutler's VMS, VAXELN and RSX-11, but also an unreleased object-based operating system developed by Cutler at Digital codenamed MICA... "The VMS kernel was primarily written in VAX MACRO [assembler], but Windows NT was designed to run on multiple instruction set architectures and multiple hardware platforms within each architecture. The platform dependencies are hidden from the rest of the system by the HAL (Hardware Abstraction Layer). While creating Windows NT, Microsoft developers rewrote VMS in C. Although they added the Win32 API, NTFS file system, GUI, and backwards compatibility with DOS, OS/2, and Win16, DEC engineers almost immediately noticed the two operating systems' internal similarities; parts of VAX/VMS Internals and Data Structures, published by Digital Press, accurately describe Windows NT internals using VMS terms. Instead of a lawsuit, Microsoft agreed to pay DEC $65–100 million, help market VMS, train Digital personnel on Windows NT, and continue Windows NT support for the DEC Alpha. "Windows NT and VMS memory management, processes, and scheduling are very similar. Windows NT's process management differs by implementing threading, which DEC did not implement until VMS 7.0 in 1995, likely to compete with Microsoft. "Like VMS, Windows NT's kernel mode code distinguishes between the "kernel", whose primary purpose is to implement processor- and architecture-dependent functions, and the "executive". This was designed as a modified microkernel, as the Windows NT kernel was influenced by the Mach microkernel developed by Richard Rashid at Carnegie Mellon University, but does not meet all of the criteria of a pure microkernel. Both the kernel and the executive are linked together into the single loaded module ntoskrnl.exe; from outside this module, there is little distinction between the kernel and the executive. Routines from each are directly accessible, as for example from kernel-mode device drivers." https://en.wikipedia.org/wiki/Windows_NT#Development https://en.wikipedia.org/wiki/Windows_NT#Development