Purpose Clear the screen fast.
Code
	call _clrLCD	;clears the screen
	
Error This may be the shortest way to clear the screen but it sure isn't the fastest. This routine has to switch ROM pages to be run which takes time. the following code is the fastest but is about 10 bytes longer. It clears (loads with l which was just cleared) byte A first. After that it copies the cleared byte A to byte B, increases both so we now are going to load the recently cleared byte B into byte C and so on.

Some people do ld (hl),$00 but since we just cleared l with ld hl,$fc00, we can just use ld (hl),l saving one byte.

Fixed Code
clear_screen:
	ld hl,$fc00	;start of video memory
	ld (hl),l	;l=$00 so we clear (hl)
	ld de,$fc01	;2nd byte in video mem
	ld bc,1023	;size of video mem-1
			; since de is start+1
	ldir		;copy already cleared
			; byte from hl into de
			; then increase so hl
			; points to what was
			; just cleared and de
			; the byte after
	ret		;we're done