org 100h
	cpu 8086

;0=00111111=3F
;1=00000110=6
;2=01011011=5B
;3=01001111=4F
;4=01100110=66
;5=01101101=6D
;6=01111101=7D
;7=00000111=7
;8=01111111=7F
;9=01101111=6F
;A=01110111=77
;B=11111111=FF
;C=00111001=39
;D=10111111=BF
;E=01111001=79
;F=01110001=71

INPUT	equ 0h
LED	equ 0h
SEGM	equ 90h


;           0    1    2      3    4      5    6     7    8      9     A     B     C      D      E    F
segtext	db 0x3F, 0x6, 0x5B, 0x4F, 0x66, 0x6D, 0x7D, 0x7, 0x7F, 0x6F, 0x77, 0xFF, 0x39, 0xBF, 0x79, 0x71
res	db 0x0


	jmp WDH

WDH:	in ax, INPUT
	mov res, ax
	and ax, 00001111b;get second nibble
	out LED, ax;debug, output to leds
	push ax;write result to stack


	mov ax, res
	mov cl, 4
	shr ax, cl;shift right 4 times
	and ax, 00001111b;might not be needed
	out LED, ax;debug, output to leds
	push ax;write result to stack


	pop ax;get from stack
	pop bx;get from stack
	
	sub ax, bx
	
	out LED, ax;output to led

	out SEGM, al;output to seven segment display
	jmp WDH