;
; 	Name: Andrew Ward
; 	Student number: 100898624
;
;	SYSC2001 Lab2
;
; Note that many lines in this program are WRONG. These lines are marked with
; a ***FIX ME comment. You need to figure out how to fix each of these lines.
;

;; CONSTANTS
; In this case we are defining the symbol 'Display' to have the value
;  of 04E9h - the address of the Libra display screen
;
Display	.EQU 04E9h	; address of Libra display

; Define a memory location where the series of numbers to be printed will be start
; ** You will have to manually enter these numbers in memory in Libra prior to running your code!
NumAddr .EQU 0050h


;
;	Program: PrtNum - print the number in AL on the screen by converting to ASCII 
;
;  	
Main:
;
; We must do some initialization
; First, we must initialize our pointer (BX) to point to the first number in memory that 
; we wish to print (You will have to set the contents of memory!)
; To do this, we use immediate addressing mode to set BX==NumAddr
;
	mov BX, NumAddr
	mov DX, Display
;
; The next statement defines another address - the beginning of the print loop
;
mainLoop:
;
; Place the number to print into the 'AH' register
;
	MOV AH,[BX]		; ***FIX ME. Should load next number to be printed into AH

; Now we need to check if it we are done printing. If AH contains a zero, then quit.
;
	cmp AH,30h		; ***FIX ME. Is the number a 0 ?
	JE EndPrt			; ***FIX ME. if so, we are done

; Now check if the number in AH is positive. 
 
	CMP AH,0
	J* posNum		; ***FIX ME. SHOULD jump to 'posNum' label iff AH is positive.

negNum:
; If we get here, then our number is negative. We need to first print a negative sign
; and then convert our number to its positive equivalent before printing

; Print a negative sign
	mov AL, BX		; ***FIX ME. Load the correct character to be printed into AL
	out DX,AL		; Send the character out to the display port
	
; Convert the negative number in AH to a positive number. This can be accomplished with a single instruction!
	* AH			; ***FIX ME. Change to the correct instruction. See the p86reference sheet.

posNum:
; If we get here, then our number is now positive (or always was).
; We need to convert the number to its ASCII equivalent and print it
printPos:
	MOV AL, AH		; ***FIX ME. Should copy number to be printed into register AL
	ADD AL, 30h		; ***FIX ME. Should add required offset to convert number to ASCII representation
	out DX,AL		; print the char

; Print a carriage return, so that the next number is printed on a new line
	MOV AL,0Dh		; ***FIX ME. Should load carriage return (CR) into AL
	out DX,AL		; print the CR
	MOV AL,0Ah		; ***FIX ME. Should load line feed (LF) into AL
	out DX,AL		; print the LF

; Look at the next number to be printed
	inc BX			; step along the array of numbers to the next number
;
; The next statement is an unconditional jump back to the beginning of the loop
; "Unconditional" means that the jump is ALWAYS taken (no CMP needed).
;
	jmp mainLoop; loop back
	
EndPrt:
	HLT			; Stop the Libra processor

.END Main