Lotus Reader
jgrahamc
13 years ago
0
9
In reply toHere is why vim uses the hjkl keys as arrow keysby freestyler
Doesn't this go way back though?

The reason that keyboard had those arrows keys on it was because those keys correspond to CTRL-H, J, K, L and the CTRL key back then worked by killing bit 6 (and bit 5) of the characters being typed.

The effect was that H which is ASCII 0x48 would become 0x08 which is backspace. If you look at an ASCII table (e.g. http://www.asciitable.com/) you will notice how the uppercase ASCII letters line up nicely with the control characters so that just dropping bit 6 will get you there. Same thing with the lowercase (drop bits 5 and 6) and you are on the control characters.

The CTRL-H, J, K, L therefore correspond to BS, LF, VT, FF. BS is backspace (i.e. left), LF (down), VT is vertical tab (so up) and FF is form feed (which in this case takes you up). I'm not sure why FF was used for up.

This is also why CTRL-I is tab, CTRL-D ends a communication. All of that goes back to teletype days. Also for telnet users out there you'll see that CTRL-[ lines up nicely with ESC. And when you see a ^@ being printed on the terminal you can see why it corresponds to a null byte.

One other interesting thing about ASCII: uppercasing and downcasing can be done by twiddling a single bit.

If you look at this picture of an ASR-33 Teletype you'll see that come of the control characters on the keyboard correspond to those in the ASCII set. This is because ASCII evolved from the earlier teletype character sets: http://upload.wikimedia.org/wikipedia/commons/0/0b/ASR-33_2....

ChuckMcM13 years ago
This is correct, and the reason they used those keys was that it was the 'home row' on a typewriter which was used in teletypes which meant your little finger could push 'ctrl' and your right hand could drive the cursor through forms without moving off the home row.

When I saw the title I was expecting to see a picture of the rogue screen. Rogue (and later hack, and nethack) is a text displayed dungeon exploration game and was often the first exposure folks got to the convention of h,j,k,l as left right up down.

I really miss having control over there. I xkeymap it there of course but some keyboards have a physically 'push-on/push-off' caps lock key there which is annoying.

kickingvegasChuckMcM13 years ago
Count me in the school of thought that the control key is meant to be to the left of the A key, just like the horn button is meant to be in the center of a car steering wheel. Every computer keyboard I worked with before the advent of IBM PCs had this arrangement. Every computer I work with now I reconfigure to swap the caps lock with the control key.

IT IS THE NATURAL ORDER OF THINGS.

mickeypkickingvegas13 years ago
It's a major frustration for me, too, as an Emacs user.

I'm still looking for a hardware dongle that does nothing but map the caps lock scan code to left ctrl. Sure, I can rebind the key (and I do) but as a contractor I move around a lot and having something that circumvents the OS entirely would come in handy.

angusangusmickeyp13 years ago
I use a keyboard that has a similar layout to that in the images above (ctrl to left of A, tilde on home key at top right etc). It's called the Happy Hacking Keyboard and is made in Japan by a Fujitsu subsidiary: see here http://en.wikipedia.org/wiki/Happy_Hacking_Keyboard. It's extremely expensive (~$300 or so) but has amazing key action and having gotten used to it I would never want to use anything else
philh13 years ago
Then the question becomes, is there a reason those control characters correspond to those letters? I have a hard time imagining a world where BS is ^Q and VT is ^V and therefore the arrow keys are spread out all over the keyboard.
fjarlq13 years ago
Good point. One question:

> I'm not sure why FF was used for up.

Did you mean "used for right"?

ScottBurson13 years ago
Actually, on a Teletype, VT went down, not up. (Vertical tab stops were settable only in hardware on most models.) And FF, which went to the top of the next page, is obviously unrelated to going right. So the correspondence was really just suggested by BS and LF; it was apparently some terminal manufacturer's idea to put up and right on the next two keys.
kragenScottBurson13 years ago
As far as I know, this was Lear Siegler's invention; I don't know of any other terminals from the era that use ^K and ^L for "move up" and "move right". (Someone did mention that ^K and ^L did do that on the ADM-3A, right?)
aptwebapps13 years ago
And that's the source of the old joke where 'overwrite' something unfortunate with ^H^H^H^H^H.