VARIOUS WAYS OF GETTING KEY INPUT FROM THE USER
-----------------------------------------------

_getkey:
This romcall waits till a key is pressed. It les the calc run in low power mode.
The contrast can be changed like in the TI-OS. But be carefull! With 2nd+[ON] the
calc can be shut down and the program crashes. It will give a err:break and the
memory will have a leak.

_getk:
The same as GETKEY in TI-BASIC. It does not wait, but it checks the entire keyboard
for a keypress. The value is stored in the register a, and in OP1 (the same format
as with TI-BASIC GETKEY:row+column).

_getcsc:
Gives the same value as _getk in teh register a, but the value is not stored in OP1.
This makes _gecsc faster than _getk. (actually the romcall _getk is a call to the 
romcall _getcsc plus the conversion to OP1)

direct input:
Very usefull for games. This is the fastest of them all. You have to check the keyboard
yourself. This way you can check only a specific group of keys, making it ultra-fast.
Make sure to use this method in your next game!!