For reference it means Ctrl+D, unless you you have a strange keyboard from Sun or something.
It's never used anymore, I suppose, except for the old school people who still have enough muscular memory built up to write it that way. I know I do; I learned it from some computer magazine in the 80's and have a hard time letting go.
I was born after the 80s, and I use that shorthand (although I suppose this probably says more about me than it does about the shorthand itself). I didn't even understand the original comment until I read through the whole thing because I mentally read it as "Ctrl+D"
So many games don't even allow you to open the console, because they assume that your key next to 1 is ~, and so don't work for § (next to 1) or altgr+¨ (the layout's ~). Or switch between looking at characters or scancodes depending on the context, and thus work in some cases but not all.
On top of that, the shortened 'ctrl' is really a terrible abbreviation. It's not obvious that it stands for 'control' and I would guess that most non-techy people would have no idea that it means this word. Plus, it's near to another key with multiple letters ('alt'). The overall effect is that 'ctrl' appears to just be a jumble of letters with some esoteric meaning. A really odd design decision. Why not just put 'control' on the key and be done with it?
Not sure I've ever seen a Mac keyboard that said "control", but maybe that's because I've mostly seen Finnish keycaps.
Perhaps the standard is something to do with the country (mine is a UK layout).
Anyways, I had the same issue when I first started using Linux. It probably took me over a year to realize the caret stood for ctrl, and that's only because I accidentally typed it in something that printed the codes literally.
Also note that on some keyboards it has the U+2638 character engraved.
Right, and the classic book The Unix Programming Environment (by Brian Kernighan and Rob Pike) uses ctl-d.