Windows NT is a clone of Digital VMS
Daeron
Mark Russinovich December 1998
Most of NT's core designers had worked on and with VMS at Digital;
some had worked directly with Cutler. How could these developers
prevent their VMS design decisions from affecting their design and
implementation of NT? Many users believe that NT's developers carried
concepts from VMS to NT, but most don't know just how similar NT and
VMS are at the kernel level (despite the Usenet joke that if you
increment each letter in VMS you end up with WNT 苦indows NT).
[...]
VMS doesn't have different OS personalities, as NT does, but its
kernel and Executive subsystems are clear predecessors to NT's.
Digital developers wrote the VMS kernel almost entirely in VAX
assembly language. To be portable across different CPU architectures,
Microsoft developers wrote NT's kernel almost entirely in C. In
developing NT, these designers rewrote VMS in C, cleaning up, tuning,
tweaking, and adding some new functionality and capabilities as they
went.
This statement is in danger of trivializing their efforts; after all,
the designers built a new API (i.e., Win32), a new file system (i.e.,
NTFS), and a new graphical interface subsystem and administrative
environment while maintaining backward compatibility with DOS, OS/2,
POSIX, and Win16. Nevertheless, the migration of VMS internals to NT
was so thorough that within a few weeks of NT's release, Digital
engineers noticed the striking similarities.
Those similarities could fill a book. In fact, you can read sections
of VAX/VMS Internals and Data Structures (Digital Press) as an
accurate description of NT internals simply by translating VMS terms
to NT terms. Table 1 lists a few VMS terms and their NT translations.
Although I won't go into detail, I will discuss some of the major
similarities and differences between Windows NT 3.1 and VMS 5.0, the
last version of VMS Dave Cutler and his team might have influenced.
This discussion assumes you have some familiarity with OS concepts
(for background information about NT's architecture, see "Windows NT
Architecture, Part 1" March 1998 and "Windows NT Architecture, Part 2"
April 1998) ...
