.ORIG x3000
START AND R0, R0, #0 ;initialize all registers to 0, except for R7
AND R1, R1, #0
AND R2, R2, #0
AND R3, R3, #0
AND R4, R4, #0
AND R5, R5, #0
AND R6, R6, #0

LD R1, User_Char ;load variables
LD R2, This_Digit
LD R3, Neg_Flag
LD R4, User_Int

LEA R0, STARTPROMPT ;print welcome message
PUTS
AND R0, R0, #0
LEA R0, OPTIONPROMPT ;print option message
PUTS
GET_USER_CHAR
AND R0, R0, #0 ;reset R0 for user input
AND R1,R1,0
GETC
OUT
ADD R1, R1, R0 ;Update User_Char
ADD R0, R0, #-16 ;Subtract 45 (-) from ASCII value in R1
ADD R0, R0, #-16
ADD R0, R0, #-13

BRz SET_NEG_FLAG ;Branch out to SET_NEG_FLAG if character in User_Char is '-'
	AND R0, R0, #0 ;Reload User_Char into R0
	ADD R0, R0, R1
	ADD R0, R0, #-16 ;Subtract 88 (X) from ASCII value in R1
	ADD R0, R0, #-16
	ADD R0, R0, #-16
	ADD R0, R0, #-16
	ADD R0, R0, #-16
	ADD R0, R0, #-8

	BRz GOODBYE ;Branch out to GOODBYE if character in User_Char is 'X'
		AND R0, R0, #0 ;Subtract 10 (Newline) from ASCII value in R1 moved to R0
		ADD R0, R0, R1
		ADD R0, R0, #-10

		BRnp UPDATE_INT ;Branch out to UPDATE_INT if character in User_Char is NOT '\n'
			ADD R3, R3, #0

			BRnz PRINT_USER_INT_LOOP ;Branch out to PRINT_USER_INT_LOOP if Neg_Flag is NOT set
				NOT R4, R4
				ADD R4, R4, #1
				BR PRINT_USER_INT_LOOP ;Branch out to PRINT_USER_INT_LOOP after taking 2SC of User_Int

SET_NEG_FLAG
ADD R3, R3, #1 ;Neg_Flag=1
BR GET_USER_CHAR ;Branch back to user input

UPDATE_INT
AND R0, R0, #0
ADD R0, R0, R1
ADD R0, R0, #-16 ;Subtract "0" in ASCII from inputted value
ADD R0, R0, #-16
ADD R0, R0, #-16
AND R2, R2, #0
ADD R2, R0, #0 ;Update This_Digit
AND R0, R0, #0 ;Reset R0 for updating User_Int
ADD R0, R4, R4 ;R0=2*R4(original)
ADD R4, R4, R4 ;R4=2*R4(original)
ADD R4, R4, R0
ADD R4, R4, R0
ADD R4, R4, R0
ADD R4, R4, R0 ;R4=10*R4(original)
ADD R4, R4, R2 ;User_Int=User_Int*10+This_Digit
BR GET_USER_CHAR ;Branch back to user input

PRINT_USER_INT_LOOP
AND R0, R0, #0
ADD R0, R0, R5 ;R5 is both an offset for array element retrieval, and loop counter
ADD R0, R0, #-15
ADD R0, R0, #-1 ;Check whether all 16 bits of User_Int were accessed

	BRz PRINT_NEWLINE ;Print '\n' after 16 binary digits of User_Int have been printed
		AND R0, R0, #0 ;clears R0 for storage of array elements
		AND R6, R6, #0 ;clears previous bit mask retrieved from Mask_Array
		LEA R6, Mask_Array ;store Mask_Array pointer in R6
		ADD R6, R6, R5 ;add offset value of R5 to Mask_Array pointer
		LDR R0, R6, #0 ;Load array value at R6+R5 into R0
		AND R0, R0, R4 ;Look at specific bit of User_Int

		BRnp ONE ;Branch out to print '1' if specific bit of User_Int is non-zero
			AND R0, R0, #0 ;Resets R0 to be used for printing '1'
			LEA R0, Zero
			LDR R0, R0, #0 ;load string "0" into R0
			PUTC
			BR INCREMENT ;Branch to INCREMENT to increment loop counter by 1

			ONE AND R0, R0, #0 ;Resets R0 to be used for printing '0'
			LEA R0, One
			LDR R0, R0, #0 ;load string "1" into R0
			PUTC

		INCREMENT ADD R5, R5, #1 ;Increments offset
		BR PRINT_USER_INT_LOOP

PRINT_NEWLINE ;Print newline, option prompt, and return to user input
AND R0, R0, #0
LEA R0, New_Line ;print newline
PUTS
AND R0, R0, #0
LEA R0, OPTIONPROMPT ;print option message
PUTS
BR START

GOODBYE
AND R0, R0, #0
LEA R0, New_Line ;print \n
PUTS
AND R0, R0, #0
LEA R0, ENDPROMPT ; prints exit message
PUTS
HALT

STARTPROMPT .STRINGZ "Welcome to the conversion program!\n"
ENDPROMPT .STRINGZ "Bye. Have a great day."
OPTIONPROMPT .STRINGZ "Enter a decimal number or X to quit:\n"
User_Char .FILL #0
This_Digit .FILL #0
Neg_Flag .FILL #0
User_Int .FILL #0
Zero .STRINGZ "0"
One .STRINGZ "1"
New_Line .STRINGZ "\n"
Mask_Array:
.FILL b1000000000000000
.FILL b0100000000000000
.FILL b0010000000000000
.FILL b0001000000000000
.FILL b0000100000000000
.FILL b0000010000000000
.FILL b0000001000000000
.FILL b0000000100000000
.FILL b0000000010000000
.FILL b0000000001000000
.FILL b0000000000100000
.FILL b0000000000010000
.FILL b0000000000001000
.FILL b0000000000000100
.FILL b0000000000000010
.FILL b0000000000000001
.END