Initial data commit

Task/Array-length/Z80-Assembly/array-length.z80

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+	org &8000
+	ld hl,TestArray
+	call GetArrayLength_WordData_NullTerminated
+	
+	call Monitor            ;show registers to screen, code omitted to keep this example short
+	
+ReturnToBasic:
+	RET
+	
+GetArrayLength_WordData_NullTerminated:
+	push hl			;we'll need this later
+loop_GetArrayLength_WordData_NullTerminated
+	ld a,(hl)		;get the low byte
+	ld e,a			;stash it in E
+	inc hl			;next byte
+	ld a,(hl)		;get the high byte
+	dec hl			;go back to low byte, otherwise our length will be off.
+	or a			;compare to zero. This is a shorter and faster way to compare A to zero than "CP 0"
+	
+	jr nz,keepGoing
+		cp e		;compare to E
+		jr z,Terminated_GetArrayLength			        ;both bytes were zero.
+KeepGoing:
+	inc hl											
+	inc hl								;next word
+	jp loop_GetArrayLength_WordData_NullTerminated	                ;back to start
+Terminated_GetArrayLength:
+	pop de		;original array address is in DE
+	;or a		;normally it's best to clear the carry, but in this situation execution only arrives here after a compare that
+                        ;resulted in an equality to zero, which means the carry is guaranteed to be cleared.
+	sbc hl,de	;there is no sub hl,de; only sbc
+	
+	srl h
+	rr l		;divide HL by 2, since each element is 2 bytes.
+	
+	ret		;returns length in hl
+
+TestArray:
+	word Apple,Orange
+	byte 0,0
+	
+Apple:
+	byte "Apple",0
+Orange:
+	byte "Orange",0