Calc

section .data

result: times 0FFh DB 0

input: times 0FFh DB 0

derr: DB 'Division by zero'

section .text

global _start

_getchar:   push edx

        push ecx

        push ebx

        push eax

        mov eax,3

        mov ebx,0

        mov ecx,result

        mov edx,1

        int 80h

        pop eax

        mov al,[ecx]

        pop ebx

        pop ecx

        pop edx

        cmp al,0Ah

        je _new

        cmp al,1Bh

        je _exit

        ret

_new:       pop eax

        call _enter

        jmp _firstf

_exit:      call _enter

        mov eax,54

        mov ebx,0

        mov ecx,5401h

        mov edx,input

        int 80h

        add edx,12

        or byte [edx],0Ah

        mov eax,54

        mov ebx,0

        mov ecx,5402h

        mov edx,input

        int 80h

        mov eax,1

        xor ebx,ebx

        int 80h

_printchar: push edx

        push ecx

        push ebx

        push eax

        mov eax,4

        mov ebx,1

        mov ecx,result

        mov edx,1

        int 80h

        pop eax

        pop ebx

        pop ecx

        pop edx

        ret

_add:       mov ecx,0FFh

        mov ebx,result

        add ebx,ecx

        movzx edx,ah

        add esi,edx

        movzx edx,al

        add edi,edx

        xor edx,edx

_ladd:      dec ebx

        dec esi

        dec edi

        cmp ah,0

        jz _noadd1

        add dl,[esi]

        dec ah

_noadd1:    cmp al,0

        jz _noadd2

        add dl,[edi]

        dec al

_noadd2:    cmp dl,0Ah

        jl _addOK

        sub dl,0Ah

        inc dh

_addOK:     mov [ebx],dl

        mov dl,dh

        xor dh,dh

        loop _ladd

        call _write

        call _enter

        jmp _firstf

_sub:       mov ecx,0FEh

        push edi

        push esi

        xor dx,dx

_scm:       cmp cl,ah

        ja _scm1

        mov dh,[esi]

        inc esi

_scm1:      cmp cl,al

        ja _scm2

        mov dl,[edi]

        inc edi

_scm2:      cmp dh,dl

        jl _subm

        jg _subp

        loop _scm

        jmp _subp

_subm:      push ax

        mov eax,4

        mov ebx,result

        mov cl,'-'

        mov [ebx],cl

        mov ebx,1

        mov ecx,result

        mov edx,1

        int 80h

        mov ebx,result

        xor cl,cl

        mov [ebx],cl

        pop ax

        xchg ah,al

        pop edi

        pop esi

        jmp _sb

_subp:      pop esi

        pop edi

_sb:        movzx ecx,ah

        mov ebx,result

        add ebx,0FEh

        add esi,ecx

_sbcp:      dec esi

        mov dl,[esi]

        mov [ebx],dl

        dec ebx

        loop _sbcp

        movzx ecx,al

        add edi,ecx

        mov ebx,result

        add ebx,0FEh

_sbloop:    mov dh,[ebx]

        dec edi

        mov dl,[edi]

        cmp dh,dl

        jge _sbOK

        add dh,0Ah

        mov esi,ebx

_sbdec:     dec esi

        mov al,[esi]

        cmp al,0

        jne _sbne

        mov al,0Ah

_sbne:      dec al

        mov [esi],al

        cmp al,9

        je _sbdec

_sbOK:      sub dh,dl

        mov [ebx],dh

        dec ebx

        loop _sbloop

        call _write

        call _enter

        jmp _firstf

_mul:       xor dx,dx

        mov cx,ax

_loopMul:   movzx ebx,dh

        add ebx,esi

        mov al,[ebx]

        movzx ebx,dl

        add ebx,edi

        mov bl,[ebx]

        mul bl

        mov bl,0Ah

        div bl

        push eax

        movzx eax,dl

        mov ebx,100h

        add ebx,eax

        movzx eax,dh

        add ebx,eax

        movzx eax,ch

        sub ebx,eax

        movzx eax,cl

        sub ebx,eax

        pop eax

        add ebx,result

        ror edx,10h

        mov dh,[ebx]

        add dh,ah

        cmp dh,0Ah

        jl _muOK

        sub dh,0Ah

        inc al

_muOK:      mov [ebx],dh

_loMul:     dec ebx

        mov dh,[ebx]

        add dh,al

        xor al,al

        cmp dh,0Ah

        jl _mulOK

        sub dh,0Ah

        inc al

_mulOK:     mov [ebx],dh

        cmp al,0

        jnz _loMul

        rol edx,10h

        inc dl

        cmp dl,cl

        jne _loopMul

        xor dl,dl

        inc dh

        cmp dh,ch

        jne _loopMul

        call _write

        call _enter

        jmp _firstf

_div:       movzx ecx,al

        mov ebx,edi

_dvzl:      mov dl,[ebx]

        cmp dl,0

        jne _dvnz

        inc ebx

        loop _dvzl

        mov eax,4

        mov ebx,1

        mov ecx,derr

        mov edx,10h

        int 80h

        call _enter

        jmp _firstf

_dvnz:      mov ebx,0FEh

_dloop:     push esi

        push edi

        mov ecx,0FEh

_dvlo:      xor dx,dx

        cmp cl,al

        ja _dcp1

        mov dl,[edi]

        inc edi

_dcp1:      push ax

        movzx ax,ah

        add bx,cx

        cmp bx,ax

        pushf

        sub bx,cx

        popf

        pop ax

        ja _dcp2

        mov dh,[esi]

        inc esi

_dcp2:      cmp dh,dl

        jg _dg

        jl _dl

        loop _dvlo

_dg:        mov ecx,ebx

        mov ebx,0FEh

        sub ebx,ecx

        add ebx,result

        mov dl,[ebx]

        inc dl

        mov [ebx],dl

        pop edi

        pop esi

        push esi

        push edi

        push ax

        push ecx

        movzx ebx,ah

        sub ebx,ecx

        add ebx,esi

        dec ebx

        movzx ecx,al

        add edi,ecx

_dsbloop:   mov dh,[ebx]

        dec edi

        mov dl,[edi]

        cmp dh,dl

        jge _dsbOK

        add dh,0Ah

        mov esi,ebx

_dsbdec:    dec esi

        mov al,[esi]

        cmp al,0

        jne _dsbne

        mov al,0Ah

_dsbne:     dec al

        mov [esi],al

        cmp al,9

        je _dsbdec

_dsbOK:     sub dh,dl

        mov [ebx],dh

        dec ebx

        loop _dsbloop

        pop ebx

        pop ax

        pop edi

        pop esi

        jmp _dloop

_dl:        pop edi

        pop esi

        cmp ebx,0

        je _dpr

        dec ebx

        jmp _dloop

_dpr:       push ax

        call _write

        pop ax

        mov edi,esi

        movzx ecx,ah

        mov ebx,ecx

        add esi,ecx

_dplo:      dec esi

        mov dl,[esi]

        cmp dl,0

        jne _dpy

        loop _dplo

        call _enter

        jmp _firstf

_dpy:       mov eax,4

        push ebx

        mov ebx,result

        mov cl,'('

        mov [ebx],cl

        mov ecx,ebx

        mov ebx,1

        mov edx,1

        int 80h

        pop ecx

        mov ebx,edi

        mov edx,ebx

        add edx,ecx

        dec edx

        call _lowrite

        mov eax,4

        mov ebx,result

        mov cl,')'

        mov [ebx],cl

        mov ecx,ebx

        mov ebx,1

        mov edx,1

        int 80h

        call _enter

        jmp _firstf

_start:     mov eax,54

        mov ebx,0

        mov ecx,5401h

        mov edx,input

        int 80h

        add edx,12

        and byte [edx],0xF5

        mov eax,54

        mov ebx,0

        mov ecx,5402h

        mov edx,input

        int 80h

_firstf:    call _getchar

        sub al,30h

        cmp al,0ah

        jnb _firstf

        mov esi,input

        mov [esi],al

        call _printchar

        inc esi

        mov ecx,0fdh

_firsto:    call _getchar

        cmp al,'+'

        je _operator

        cmp al,'-'

        je _operator

        cmp al,'*'

        je _operator

        cmp al,'/'

        je _operator

        sub al,30h

        cmp al,0ah

        jnb _firsto

        mov [esi],al

        call _printchar

        inc esi

        loop _firsto

_operatorl: call _getchar

        cmp al,'+'

        je _operator

        cmp al,'-'

        je _operator

        cmp al,'*'

        je _operator

        cmp al,'/'

        je _operator

        jmp _operatorl

_operator:  mov dl,al

        call _printchar

_secondf:   call _getchar

        sub al,30h

        cmp al,0ah

        jnb _secondf

        mov [esi],al

        call _printchar

        mov ebx,esi

        mov edi,input

        sub ebx,edi

        mov ah,bl

        mov ecx,0feh

        mov edi,esi

        inc esi

        sub cl,bl

        jz _endinput

_secondo:   call _getchar

        cmp al,'='

        je _endinput

        sub al,30h

        cmp al,0Ah

        jnb _secondo

        mov [esi],al

        call _printchar

        inc esi

        loop _secondo

_endinput:  sub esi,edi

        mov ebx,esi

        mov al,bl

        mov esi,input

        mov ecx,result

        mov bl,'='

        mov [ecx],bl

        call _printchar

        mov ecx,0FFh

        mov ebx,result

        mov dh,0

_clean:     mov [ebx],dh

        inc ebx

        loop _clean

        cmp dl,'+'

        je _add

        cmp dl,'-'

        je _sub

        cmp dl,'*'

        je _mul

        jmp _div

_write:     mov ebx,result

        mov edx,ebx

        add edx,0FEh

        mov ecx,0FFh

_lowrite:   cmp ebx,edx

        jnb _add30

        mov al,[ebx]

        cmp al,0

        je _lwrite

        mov edx,ebx

_add30:     mov al,30h

        add [ebx],al

_lwrite:    inc ebx

        loop _lowrite

        mov ecx,edx

        mov edx,ebx

        sub edx,ecx

        mov eax,4

        mov ebx,1

        int 80h

        ret

_enter:     mov eax,4

        mov ebx,1

        mov ecx,result

        mov edx,0A01h

        mov [ecx],dh

        xor dh,dh

        int 80h

        ret