[Coco] Mod10 Suggestions

[William Mikrut]

For years I have been an IBM programmer and have done well in that area --
for 30 years now.
I started with a CoCo2 back in 84/85 - and ML has always fascinated me --
yet eluded me to a degree.

With the advent of hardware (FPGAs) -- seems like we could do some pretty
coll stuff.
So, I try to enter into the 8 Bit world that is CoCo and get down to some
programming.

Following is a MOD10 program I have used for years in IBM programs.
I have translated it the best I can...I am sure it is not the most
efficient... and I have much to learn.

Attached is the MOD10 code.
I am hoping for constructive comments so I can learn, and move on to other
projects!
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	ORG	$1200
CCD	RMB	16	;Credit Card Number
RESULT	RMB	1	;Result for caluclations
STATUS	RMB	1	;#$00=Bad CCD #, #$FF=Good CCD#

START	LEAX	CCD,pcr	;Load the location of the number
	
	CLRB		
	STB	#RESULT	;Clear the result field
	LDA	#16	;16 Times through the loop

LOOP.00	DECA
	LDB	A,X	;Load a With X
	
	BITA	#1	;Test for Even/Odd Numbers
	BNE	PROC.02		
	
PROC.00	PSHS	A	;We need to multiply the number by 2
	LDA	#2
	MUL
	PULS	A
	CMPB	#10
	BLO	PROC.02
	
PROC.01	SUBB	#10	;If over 10, Add the 2 numbers together.
	INCB		;Since the biggest# can be 18, Sub 10 and Increment B once
	
PROC.02	ADDB	RESULT	;Accumulate the result
	STB	#RESULT
	
	CMPA	#0	;Are we done with all 16 numbers?
	BNE	LOOP.00
	
CHK.00	CMPB	#10	;This is a division trick.  If the result is divisible by 10
	BLO	CHK.01	;it's a good card number.  Keep sbtracting 10 until the result
	SUBB	#10	;is under 10.  If so and B is zero, we have a good number.
	BRA	CHK.00	;Else it's a bad number
CHK.01	CMPB	#0
	BEQ	GOOD.00
	LDA	#$00
	BRA	SHOW.00
	
GOOD.00	LDA	#$FF
	
SHOW.00	STA	#STATUS
	
ENDPGM	RTS	
	END	START