"Digital developers wrote the VMS kernel almost entirely in VAX assembly language. To be portable across different CPU architectures, Microsoft developers wrote

"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." https://www.itprotoday.com/compute-engines/windows-nt-and-vms-rest-story https://www.itprotoday.com/compute-engines/windows-nt-and-vm...