Hoi,
coi :-)
Currently on UNIX, there is no B command.
A script named "B" (note capital letter) was written at some point that performed the explicit steps shown in the B manual. This was evidently renamed to "b" at some point. "All is in flux."
I came to this question because I was looking for one letter
commands. I always thought them to be a reserved namespace for the
user ...
By no means, at least not by now. "x" is the name of the raw X11 binary, and "w" is a variant of "who" that displays the idle time (similar to "finger") and the last command executed. The J and K language interpreters from the APL dharma line (and consequently oriented toward terseness) are executed as "J" and "k" respectively.