Windows NT and VMS: the rest of the story

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.

Another old article, from November 1998 this time, also by Mark Russinovich.


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