But for some reason, drive letters starting with C feel completely natural, too. Maybe it's because C is also the first note in the most widely known musical scale. We can totally afford to waste two drive letters at the start, right?
Our first home computer (1989 or 1990?) was a 386SX with a 40MB hard disk (so maybe we were bourgeois). My dad had to partition it into a 32MB C drive and an 8MB D drive, because the DOS version (3.3?) had a 32MB maximum filesystem size. It had two separate 5.25 inch floppy drives, a 1.2MB and a 360KB - although the 1.2MB drives could read 360KB disks, they couldn’t write them in a form readable by 360KB drives, or something like that. And later (circa 1991) we got a 3.5 inch floppy drive too, which became drive A, the 1.2MB became drive B, and the 360KB was relegated to drive E. The FDC that came with the computer (back then they were ISA cards, hadn’t been integrated with the motherboard yet) only supported two drives, so he had to buy a new one that supported four.
My first contact with PCs was in 1988 and they all had HDDs and were definitely not "IBM PC" but clones. That said, that's just my experience so YMMV.
MIT, where I was at school then, had some IBM PC XTs with 10 MB hard drives, but most of their computer resources were time-sharing DEC VAX machines. You could go to one of several computer labs to get on a terminal, or even dial into them--I did the latter from my PC (the one above) using a 2400 baud modem, which was fast for the time.
We had a dumb "computer literacy" class taught in an computer lab full of PS/2 Model 25s with no hard drives, and were each issued a bootable floppy disk containing both Microsoft Works and our assignment files (word processing documents, spreadsheets, etc.), which we turned in at the end of class for grading.
We started Works in the usual way, by typing "works" at the MS-DOS prompt.
One day, out of boredom, I added "PROMPT Password:" to AUTOEXEC.BAT on my disk, changing the DOS prompt from "A:\>" to "Password:" when booted from my disk.
Two days later, I got called into the dean's office, where the instructor demanded to know how I used my disk to "hack the network" — a network that, up until this point, I didn't even know existed, as the lab computers weren't connected to anything but power — and "lock me out of my computer", and threatened suspension unless and until I revealed the password.
After a few minutes trying to explain that no password existed to a "computer literacy" instructor who clearly had no idea what either AUTOEXEC.BAT or the DOS prompt was, nor why booting a networked computer from a potentially untrustworthy floppy disk was a terrible idea, I finally gave in.
"Fine. The password is works. Can I go now?"
The irony, it was actually faster doublespaced/stacked.
In Russia, we had class full of IBM PCs without hard drives in school - you had to juggle floppies - and that was early 90s. And that was a fancy school.
the linked source checks out. diskcopy will also do this for you if you give it source = dest.
c:\> subst d: c:
On my laptop, D is the SD card slot. On my desktop, it's the 2nd SSD.
We used to set our machines so the CD-ROM was always drive L. This way we always had 'room' to add HDs so there was no gap in the alphabetical sequence. Drive D - data drive, E - swapfile, etc.
Test and external drives (being temporary) were assigned letters further down than L. Sticking reasonably rigidly to this nomenclature avoided stuff-up such as cloning an empty drive onto one with data on it (cloning was a frequent activity).
Incidentally, this rule applied to all machines, a laptop with HD would have C drive and L as the CD-ROM. Machines with multiple CD-ROMs would be assigned L, M and so on.
I mainly did it so that CD installs wouldn’t lose their install drive since even Windows tracked it by the absolute path. Not as important with everything installed by download and Windows copying the install media to the hard drive anyway.
Between CD/DVD drives, writers, Zip Drives, and extra hard drives, it wasn't unusual for a workstation to naturally end up with G: or H:, before mapped network storage became common.
As another commenter mentioned, when you didn't have a second floppy drive, A: and B: mapped to two floppy disks in the same floppy drive, with DOS pausing and asking you to insert the other floppy disk when necessary. Which explains why, even on single-floppy computers, the hard disk was at C: and not B: (and since so much software ended up expecting it, the convention continued even on computers without any floppy disk drive).
I also use the drive letter assignment feature, so my external USB drive is always drive X.