	Depending upon hardware or operating system or NetHack's interface,
	some keystrokes may be off-limits.

	For example, ^S and ^Q are often used for XON/XOFF flow-control,
	meaning that ^S suspends output and subsequent ^Q resumes suspended
	output.  When that it the case, neither of those characters will
	reach NetHack when it is waiting for a command keystroke.  So they
	aren't used as commands, but 'whatdoes' might not be able to tell
	you that if they don't get passed through to NetHack.

	^M or <return> or <enter> is likely to be transformed into ^J or
	<linefeed> or 'newline' before being passed to NetHack for handling.
	So it isn't used as a command, and 'whatdoes' might seem as if it
	is reporting the wrong character but will be operating correctly if
	it describes ^J when you type ^M.

	A NUL character, which is typed as ^<space> on some keyboards,
	^@ on others, and maybe not typeable at all on yet others, is not
	used as a command, and will be converted into ESC before reaching
	'whatdoes'.  Unlike ^M, this transformation is performed within
	NetHack.  But like ^M, if you type NUL and get feedback about ESC,
	the situation is expected.

	ESC itself is a synonym for ^[, and is another source of oddity.
	Various function keys, including cursor arrow keys, may transmit
	an "escape sequence" of ESC + [ + other stuff, confusing NetHack
	as to what command was intended since the ESC will be processed
	and then whatever follows will seem to NetHack like--and be used
	as--something typed by the user.  (If you press a function key and
	a menu of the armor your hero is wearing appears, what happened
	was that an escape sequence was sent to NetHack, its ESC aborted
	any pending key operation, its '[' was then treated as a command
	to show worn armor, and the "other stuff" probably got silently
	discarded as invalid choices while you dismissed the menu.)

	If you have NetHack's 'altmeta' option enabled, meaning that the
	<alt> or <option> key, when used as shift while typing some other
	character, transmits ESC and then the other character so NetHack
	should treat that other character as a meta-character, then ESC
	takes on added potential for confusion.  Implicit in the handling
	of a two character sequence ESC + something is the fact that when
	NetHack sees ESC, it needs to wait for another character before
	it can decide what to do.  So if you type ESC manually, you'll
	need to type it a second time or NetHack will sit there waiting.
	(It will then be treated as if you typed ESC rather than M-ESC.)

	On some systems, typing ^\ will send a QUIT signal to the current
	process, probably killing it and possibly causing it to save a
	core dump.  It is not used for any NetHack command, so don't type
	that character.

	One last note:  characters shown as ^x mean that you should hold
	down the <control> or <ctrl> key as a shift and then type 'x'.
	Control characters are all implicitly uppercase, but you don't
	need to press the shift key while typing them.  The opposite is
	true for meta-characters:  they can be either case, so you need
	to use shift as well as <meta> or <alt> to generate an uppercase
	letter meta-character.
