;
; UFRGS - INF - M Johann - 2023 - johann@inf.ufrgs.br
; Simple multiplication of pairs of numbers in a vector
; Stores the results after this vector

; ----- DATA 

		org	h80
size:		db	18
ptr:		db	0
vector:		dab	2,2,7,5,10,10,12,12,16,16,0,7,7,0,3,3,1,200
result: 	db	0		; here goes the result
					; calculated after vector
		
; ----- BEGIN MAIN CODE 

		org	0

startup:	; start by computing where the result goes

		LDR	A,size		
		STR	A,ptr	
		ADD 	A,ptr		; ptr = 2 * size
		LDR	A,#vector
		ADD	A,ptr		; adds vector address
		STR 	A,ptr		; and stores result ptr 

		LDR 	X,#0		; X is vector index
beginmul:	
		LDR	A,#0		; start with 0
		STR	A,ptr,I		; 
		LDR	A,vector,X	; reads operand
		LDR	B,vector+1,X	; reads multiplier
loop: 		
		JZ 	next		; multiply loop ended?
		ADD	A,ptr,I		; adds to result
		STR	A,ptr,I		; store result
		LDR	A,vector,X	; recover operand
		SUB	B,#1		; decrement loop
		JMP	loop

next:		LDR 	A,ptr		; increment pointer
		ADD 	A,#1
		STR	A,ptr

		ADD	X,#2		; next numbers
		SUB	X,size		; size must be exact, even
		JZ	finish
		ADD	X,size
		JMP 	beginmul

finish:		HLT
		
; END OF FILE