I am making an LC3 assembly program that calculates x factorial. I have this label called "OUTERLOOP" that is utilized as long as my counter value is not negative. However, the assembler is giving me this error: "32: label OUTERLOOP has already appeared." It does not give me this error for the inner loop. For some reason, it looks like it thinks I'm trying to name another address with OUTERLOOP again when I'm trying to get it to branch back to the OUTERLOOP address. Any ideas?
; This program calculates X! (X factorial). It can calculate
; different numbers (4!, 6!, etc.) by changing the value of the first memory
; location at the bottom of the code. It is currently set up to calculate
; 5!. The program does not account for zero or negative numbers as input.
; This program primarily uses registers in the following manner:
; R0 contains 0 (registers contain zero after reset)
; R1 contains multiplication result (6x5 = 30, 30x4 = 120, etc)
; R2 contains -1
; R3 contains counter for outer loop
; R4 contains counter for inner loop
; R5 contains current sum
.ORIG x3000
LD R1,INPUT ; R1 contains input number
LD R2,xFFFF ; R2 contains -1
ADD R3,R1,R2 ; R3 contains input number -1
ADD R3,R3,R2 ; R3 contains input number -2
; (initializes outer count)
OUTERLOOP ADD R4,R0,R3 ; Copy outer count into inner count
; This loop multiplies via addition (6x5 = 6+6+6+6+6 = 30,
; 30x4 = 30+30+30+30 = 120, etc)
INNERLOOP ADD R5,R5,R1 ; Increment sum
ADD R4,R4,R2 ; Decrement inner count
BRzp INNERLOOP ; Branch to inner loop if inner count
; is positive or zero
ADD R1,R0,R5 ; R1 now contains sum result from inner loop
AND R5,R5,#0 ; Clear R5 (previous sum) to 0
ADD R3,R3,R2 ; Decrement outer count
BRpz OUTERLOOP ; Branch to outer loop if outer count
; is positive or zero
ST R1,INPUT ; This address contains X!
TRAP x25 ; HALT
INPUT .FILL x0005 ; Input for X!, in this case X = 5
.FILL x0000
.FILL xFFFF ; 2's complement of 1 (i.e. -1)
.FILL x0000 ; At program completion, the result is
; stored here
.END
