%define CURRENT_ADDR cs:di

; Prints a null terminated string of your choice.
; Arguments:
;     CS:DI - pointer to the string you want to print
;     BL - 0 prints newline, otherwise no
print
	pusha
	mov ah, 0Eh ; teletype print
.write2
	mov al, [CURRENT_ADDR] ; get current char and put it in al
	cmp al, 0 ; check if al is null (string terminator)
	je .newline ; if it is, start a new line
	int 10h ; otherwise write the char
	inc di ; increment pointer to string
	jmp .write2 ; jump back to this section
.newline
	cmp bl, 1
	je .done
	mov al, 0Dh ; carriage return
	int 10h
	mov al, 0Ah ; line feed
	int 10h
.done
	popa
	ret ; return

; Prints a word (16-bit value) in hex format.
; Arguments:
;     DX - word to print
;     BL - 0 will print a newline, 1 won't
print_word
	pusha ; push all regs to stack
	mov di, HEX_OUT+5 ; set destination index to last char in HEX_OUT
	mov ax, dx ; copy argument to accumulator
	and al, 00001111b ; extract the low nibble of the low half of the accumulator
	call .compare ; fill in the string with correct value
	dec di ; decrement string pointer
	mov ax, dx ; copy argument to accumulator
	and al, 11110000b ; extract high nibble of low half of accumulator
	shr al, 4 ; shift high nibble to low nibble
	call .compare ; fill in string with correct value
	dec di
	mov al, ah ; copy high portion of accumulator to low
	and al, 00001111b ; 
	call .compare
	dec di
	mov al, ah
	and al, 11110000b
	shr al, 4
	call .compare
	mov di, HEX_OUT
	call print ; write string
	popa
	ret

.compare
	cmp al, 0 ; compare al with 0
	jne .one ; if not equal, compare with 1
	mov byte [CURRENT_ADDR], '0' ; set character to ASCII 0
	ret ; return
.one
	cmp al, 1
	jne .two
	mov byte [CURRENT_ADDR], '1'
	ret
.two
	cmp al, 2
	jne .three
	mov byte [CURRENT_ADDR], '2'
	ret
.three
	cmp al, 3
	jne .four
	mov byte [CURRENT_ADDR], '3'
	ret
.four
	cmp al, 4
	jne .five
	mov byte [CURRENT_ADDR], '4'
	ret
.five
	cmp al, 5
	jne .six
	mov byte [CURRENT_ADDR], '5'
	ret
.six
	cmp al, 6
	jne .seven
	mov byte [CURRENT_ADDR], '6'
	ret
.seven
	cmp al, 7
	jne .eight
	mov byte [CURRENT_ADDR], '7'
	ret
.eight
	cmp al, 8
	jne .nine
	mov byte [CURRENT_ADDR], '8'
	ret
.nine
	cmp al, 9
	jne .ten
	mov byte [CURRENT_ADDR], '9'
	ret
.ten
	cmp al, 0Ah
	jne .eleven
	mov byte [CURRENT_ADDR], 'A'
	ret
.eleven
	cmp al, 0Bh
	jne .twelve
	mov byte [CURRENT_ADDR], 'B'
	ret
.twelve
	cmp al, 0Ch
	jne .thirteen
	mov byte [CURRENT_ADDR], 'C'
	ret
.thirteen
	cmp al, 0Dh
	jne .fourteen
	mov byte [CURRENT_ADDR], 'D'
	ret
.fourteen
	cmp al, 0Eh
	jne .fifteen
	mov byte [CURRENT_ADDR], 'E'
	ret
.fifteen
	mov byte [CURRENT_ADDR], 'F'
	ret

HEX_OUT db "0x0000", 0