Numeric codes of non-standard function keys

[Anton Vidovic]

Hello,

The numeric codes retured by getch for the more common function
keys KEY_BREAK (257) to KEY_RESIZE (410) are hard-coded in
curses.h.

Is there a logic behind the assignmet of the numeric codes of the
non-standard function keys, for example the xterm range 517 (kDC3)
to 568 (kUP7)? Are those used as bitmasks for the modifiers
Ctrl, Shift and Alt? If yes, could you point me to where this is
described? If not, is there a way to find out which modifier is
active for that key other than parsing the escape sequences?

If other terminals/emulators have other function keys, which
codes are assigned to them?

Which numeric codes are used for new sequences that can be added
by `define_key', is there a logic or a defined range behind that?

Thanks and kind regards,
Anton