I wrote recently about buying a Digital (DEC) vt420 and hooking it up to Linux. Among my observations on the vt420, which apparently were among the most popular to use with Unix systems, are these:
- DEC keyboards had no Esc key
- DEC keyboards had no key that could be used as Alt or Meta
The two most popular historic editors on Unix, vi and emacs, both make heavy use of these features (Emacs using Esc when Alt or Meta is unavailable). Some of the later entries in the DEC terminal line, especially the vt510, supported key remapping or alternative keyboards, which can address the Esc issue, but not entirely.
According to the EmacsOnTerminal page and other research, at least the vt100 through the vt420 lacked Esc by default. Ctrl-3 and Ctrl-[ could send the character. However, this is downright terrible for both vi and Emacs (as this is the only way to trigger meta commands in Emacs).
What’s more, it seems almost none of these old serial terminal support hardware flow control, and flow control is an absolute necessity on many. That implies XON/XOFF, which use Ctrl-S and Ctrl-Q — both of which are commonly used in Emacs.
Both vi and Emacs trace their roots back to the 1970s and were widely used in the serial terminal era, running on hardware dominated by DEC and its serial terminals.
So my question is: why would both of these editors be developed in such a way that they are downright inconvenient to use on the hardware on which they most frequently ran?
Update 2019-11-20: It appears that the vt100 did have the Esc key, but it was dropped with the vt220. At least the vt420 and later, and possibly as far back as the vt220, let you map one of a few other keys to be Esc. This still leaves the Ctrl-S mystery in Emacs though.