INT 10,9 - Write Character and Attribute at Cursor Position

	AH = 09
	AL = ASCII character to write
	BH = display page  (or mode 13h, background pixel value)
	BL = character attribute (text) foreground color (graphics)
	CX = count of characters to write (CX >= 1)

	returns nothing

	- does not move the cursor
	- in graphics mode (except mode 13h), if BL bit 7=1 then
	  value of BL is XOR'ed with the background color