On: Why Does Windows Really Use Backslash as Path Separator?

[p4bl0]

So this is very interesting, but doesn't go into the next obvious question: why did TOPS-10 use forward slashes as command switch?

[eschaton → p4bl0]

That was a general DEC-ism, not just a TOPS-10 thing.

[mcluck → eschaton]

So let's follow it to the end. Who first started using slashes that way and why?

[kragen → mcluck]

You probably want to read https://news.ycombinator.com/item?id=20007305 and https://news.ycombinator.com/item?id=20007259.

[aap_ → mcluck]

Probably TOPS-10, or rather the PDP-6 Monitor (which later was renamed TOPS-10)