Escape sequences. The current system is basically a giant bag of baggage we inherited from ye olden days. If implemented today I'd guess it would make much more sense to let a terminal application determine the actual key combination pressed (such as C-Tab, for example). I'm pretty sure that wouldn't be very easy to change, though (at least while keeping compatibility).
Edit: To clarify: I'm referring mainly to the fact that certain key combinations are not mapped at all, while other ones are synonyms for special keys, i.e.: ^[ is Escape,^I is Tab etc.
Edit: To clarify: I'm referring mainly to the fact that certain key combinations are not mapped at all, while other ones are synonyms for special keys, i.e.: ^[ is Escape,^I is Tab etc.
cf.: http://wiki.bash-hackers.org/scripting/terminalcodes