INT 21,A - Buffered Keyboard Input

	AH = 0A
	DS:DX = pointer to input buffer of the format:

	| max | count |  BUFFER (N bytes)
	   |	  |	     `------ input buffer
	   |	  `------------ number of characters returned (byte)
	   `-------------- maximum number of characters to read (byte)

	returns nothing

	- since strings can be pre-loaded, it is recommended that the
	  default string be terminated with a CR
	- N bytes of data are read from STDIN into buffer+2
	- max buffer size is 255, minimum buffer size is 1 byte
	- chars up to and including a CR are placed into the buffer
	  beginning at byte 2;	Byte 1 returns the number of chars
	  placed into the buffer  (extended codes take 2 characters)
	- DOS editing keys are active during this call
	- INT 23 is called if Ctrl-Break or Ctrl-C detected