.model small

.stack 100h

.data
	ten dw 10
	FirstNumber dw 0
	SecondNumber dw 0
	TempVal1 dw 0
	TempVal2 dw 0

.code
; this macro prints a string that is given as a parameter, example:
; PRINTN 'hello world!'
; the same as PRINT, but new line is automatically added.
PRINTN   MACRO   sdat
LOCAL   next_char, s_dcl, printed, skip_dcl

PUSH    AX      ; store registers...
PUSH    SI      ;

JMP     skip_dcl        ; skip declaration.
        s_dcl DB sdat, 0Dh,0Ah, 0

skip_dcl:
        LEA     SI, s_dcl

next_char:
        MOV     AL, CS:[SI]
        CMP     AL, 0
        JZ      printed
        INC     SI
        MOV     AH, 0Eh ; teletype function.
        INT     10h
        JMP     next_char
printed:

POP     SI      ; re-store registers...
POP     AX      ;
ENDM

PRINT   MACRO   sdat
LOCAL   next_char, s_dcl, printed, skip_dcl

PUSH    AX      ; store registers...
PUSH    SI      ;

JMP     skip_dcl        ; skip declaration.
        s_dcl DB sdat, 0

skip_dcl:
        LEA     SI, s_dcl

next_char:
        MOV     AL, CS:[SI]
        CMP     AL, 0
        JZ      printed
        INC     SI
        MOV     AH, 0Eh ; teletype function.
        INT     10h
        JMP     next_char
printed:

POP     SI      ; re-store registers...
POP     AX      ;
ENDM

; this macro prints a char in AL and advances
; the current cursor position:
PUTC    MACRO   char
        PUSH    AX
        MOV     AL, char
        MOV     AH, 0Eh
        INT     10h
        POP     AX
ENDM
	MAIN PROC

		call init
		call clearScreen

		printn 'Zakres liczbowy 0-32765'

		print 'Wpisz pierwsza liczbe: '
		call scan_num

		mov FirstNumber, cx
		xor cx, cx

		call printNewLine

		print 'Wpisz druga liczbe: '
		call scan_num
		mov SecondNumber, cx
		xor cx, cx

		call printNewLine

		printn '(x1+(x1-x2): '
		call printAddNumbers
		call printNewLine


		jmp EndOfProgram

	clearRegisters:
		xor ax, ax
		xor bx, bx
		xor cx, cx
		ret

	printAddNumbers:
		call clearRegisters

		; (x1-x2)
		mov cx, FirstNumber
		mov TempVal1, cx
		sub cx, SecondNumber
		mov TempVal2, cx ; wynik x1 - x2
		xor cx, cx

		; cx + tempVal1
		mov cx, TempVal1
		add cx, TempVal2

		mov ax, cx
		xor cx, cx
		call print_num
		ret

	printNewLine:
		mov ah, 2

		mov dl, 13
		int 21h

		mov dl, 10
		int 21h
		ret

	init:
		mov ax, @data
		mov ds, ax
		ret

	clearScreen:
		mov ax, 3
		int 10h
		ret

	EndOfProgram:
		mov ah, 4ch
		int 21h
		ret
MAIN ENDP

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;;; these functions are copied from emu8086.inc ;;;
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;


; gets the multi-digit SIGNED number from the keyboard,
; and stores the result in CX register:
SCAN_NUM        PROC    NEAR
        PUSH    DX
        PUSH    AX
        PUSH    SI

        MOV     CX, 0

        ; reset flag:
        MOV     CS:make_minus, 0

next_digit:

        ; get char from keyboard
        ; into AL:
        MOV     AH, 00h
        INT     16h
        ; and print it:
        MOV     AH, 0Eh
        INT     10h

        ; check for MINUS:
        CMP     AL, '-'
        JE      set_minus

        ; check for ENTER key:
        CMP     AL, 0Dh  ; carriage return?
        JNE     not_cr
        JMP     stop_input
not_cr:


        CMP     AL, 8                   ; 'BACKSPACE' pressed?
        JNE     backspace_checked
        MOV     DX, 0                   ; remove last digit by
        MOV     AX, CX                  ; division:
        DIV     CS:ten                  ; AX = DX:AX / 10 (DX-rem).
        MOV     CX, AX
        PUTC    ' '                     ; clear position.
        PUTC    8                       ; backspace again.
        JMP     next_digit
backspace_checked:


        ; allow only digits:
        CMP     AL, '0'
        JAE     ok_AE_0
        JMP     remove_not_digit
ok_AE_0:
        CMP     AL, '9'
        JBE     ok_digit
remove_not_digit:
        PUTC    8       ; backspace.
        PUTC    ' '     ; clear last entered not digit.
        PUTC    8       ; backspace again.
        JMP     next_digit ; wait for next input.
ok_digit:


        ; multiply CX by 10 (first time the result is zero)
        PUSH    AX
        MOV     AX, CX
        MUL     CS:ten                  ; DX:AX = AX*10
        MOV     CX, AX
        POP     AX

        ; check if the number is too big
        ; (result should be 16 bits)
        CMP     DX, 0
        JNE     too_big

        ; convert from ASCII code:
        SUB     AL, 30h

        ; add AL to CX:
        MOV     AH, 0
        MOV     DX, CX      ; backup, in case the result will be too big.
        ADD     CX, AX
        JC      too_big2    ; jump if the number is too big.

        JMP     next_digit

set_minus:
        MOV     CS:make_minus, 1
        JMP     next_digit

too_big2:
        MOV     CX, DX      ; restore the backuped value before add.
        MOV     DX, 0       ; DX was zero before backup!
too_big:
        MOV     AX, CX
        DIV     CS:ten  ; reverse last DX:AX = AX*10, make AX = DX:AX / 10
        MOV     CX, AX
        PUTC    8       ; backspace.
        PUTC    ' '     ; clear last entered digit.
        PUTC    8       ; backspace again.
        JMP     next_digit ; wait for Enter/Backspace.


stop_input:
        ; check flag:
        CMP     CS:make_minus, 0
        JE      not_minus
        NEG     CX
not_minus:

        POP     SI
        POP     AX
        POP     DX
        RET
make_minus      DB      ?       ; used as a flag.
SCAN_NUM        ENDP

; this procedure prints number in AX,
; used with PRINT_NUM_UNS to print signed numbers:
PRINT_NUM       PROC    NEAR
        PUSH    DX
        PUSH    AX

        CMP     AX, 0
        JNZ     not_zero

        PUTC    '0'
        JMP     printed

not_zero:
        ; the check SIGN of AX,
        ; make absolute if it's negative:
        CMP     AX, 0
        JNS     positive
        NEG     AX

        PUTC    '-'

positive:
        CALL    PRINT_NUM_UNS
printed:
        POP     AX
        POP     DX
        RET
PRINT_NUM       ENDP



; this procedure prints out an unsigned
; number in AX (not just a single digit)
; allowed values are from 0 to 65535 (FFFF)
PRINT_NUM_UNS   PROC    NEAR
        PUSH    AX
        PUSH    BX
        PUSH    CX
        PUSH    DX

        ; flag to prevent printing zeros before number:
        MOV     CX, 1

        ; (result of "/ 10000" is always less or equal to 9).
        MOV     BX, 10000       ; 2710h - divider.

        ; AX is zero?
        CMP     AX, 0
        JZ      print_zero

begin_print:

        ; check divider (if zero go to end_print):
        CMP     BX,0
        JZ      end_print

        ; avoid printing zeros before number:
        CMP     CX, 0
        JE      calc
        ; if AX<BX then result of DIV will be zero:
        CMP     AX, BX
        JB      skip
calc:
        MOV     CX, 0   ; set flag.

        MOV     DX, 0
        DIV     BX      ; AX = DX:AX / BX   (DX=remainder).

        ; print last digit
        ; AH is always ZERO, so it's ignored
        ADD     AL, 30h    ; convert to ASCII code.
        PUTC    AL


        MOV     AX, DX  ; get remainder from last div.

skip:
        ; calculate BX=BX/10
        PUSH    AX
        MOV     DX, 0
        MOV     AX, BX
        DIV     CS:ten  ; AX = DX:AX / 10   (DX=remainder).
        MOV     BX, AX
        POP     AX

        JMP     begin_print

print_zero:
        PUTC    '0'

end_print:

        POP     DX
        POP     CX
        POP     BX
        POP     AX
        RET
PRINT_NUM_UNS   ENDP

GET_STRING      PROC    NEAR
PUSH    AX
PUSH    CX
PUSH    DI
PUSH    DX

MOV     CX, 0                   ; char counter.

CMP     DX, 1                   ; buffer too small?
JBE     empty_buffer            ;

DEC     DX                      ; reserve space for last zero.


;============================
; Eternal loop to get
; and processes key presses:

wait_for_key:

MOV     AH, 0                   ; get pressed key.
INT     16h

CMP     AL, 0Dh                  ; 'RETURN' pressed?
JZ      exit_GET_STRING


CMP     AL, 8                   ; 'BACKSPACE' pressed?
JNE     add_to_buffer
JCXZ    wait_for_key            ; nothing to remove!
DEC     CX
DEC     DI
PUTC    8                       ; backspace.
PUTC    ' '                     ; clear position.
PUTC    8                       ; backspace again.
JMP     wait_for_key

add_to_buffer:

        CMP     CX, DX          ; buffer is full?
        JAE     wait_for_key    ; if so wait for 'BACKSPACE' or 'RETURN'...

        MOV     [DI], AL
        INC     DI
        INC     CX

        ; print the key:
        MOV     AH, 0Eh
        INT     10h

JMP     wait_for_key
;============================

exit_GET_STRING:

; terminate by null:
MOV     DI, 0

empty_buffer:

POP     DX
POP     DI
POP     CX
POP     AX
RET
GET_STRING      ENDP
end