I remember it from the days around the turn of the century, when I studied Microsoft NT4 server and the kernel.
In in our country hospitals and the transport sector had to roll out NT4 and MS offered official training.
Most of the then students were linux admins with years and years of experience.
I learned a lot during that frantic course, the certificate still hangs on the wall,
and I now wonder who of you still use the odd MS-DOS command from time to time,
like netstat -an given in from the command prompt for instance…
I got very good with up to MS-DOS 5.0 in early 1999 because the product on which I worked still used that. But, then I changed jobs and there was no use for MS-DOS there. Instead now the focus was on learning and using Windows 98.
I have not touched MS-DOS since and consequently, I have probably forgotten 90% of what I used to know.