.model tiny
    .code
    .386
    org 100h
start:
vvod1:
    xor eax,eax
    xor edx,edx
    call clrscr
    mov ah,9
    mov dx,offset message1
    int 21h
    mov ah,08h
    int 21h
    cmp al,'+'
    je cloj
    cmp al,'-'
    je vich
    cmp al,'/'
    je dele
    cmp al,'*'
    je rr1
    jmp rr
rr1:    jmp umnoj
rr: cmp al,'q'
    je quit
    cmp al,'Q'
    je quit
    jmp short vvod1
quit:
    ret
cloj:
    call clrscr

    call aa1
    push dx
    call bb1
    pop dx
    add ax,dx

    call print

    call endstrd
    mov ah,9
    mov dx,offset message2
    int 21h
    mov ah,08h
    int 21h
    jmp vvod1
vich:

    call clrscr
    call aa1
    push dx
    call bb1

    pop dx
    sub dx,ax
    mov ax,dx

    call print

    call endstrd
    mov ah,9
    mov dx,offset message2
    int 21h
    mov ah,08h
    int 21h
    jmp vvod1

dele:
    call clrscr
    call aa1
    push dx
    call bb1

    pop dx
    xchg dx,ax
    mov cx,dx
    xor dx,dx
    div cx

    call print

    call endstrd
    mov ah,9
    mov dx,offset message2
    int 21h
    mov ah,08h
    int 21h


    jmp vvod1
umnoj:
    call clrscr
    call aa1
    push dx
    call bb1
    pop dx

    mul edx

    call print

    call endstrd
    mov ah,9
    mov dx,offset message2
    int 21h
    mov ah,08h
    int 21h
    jmp vvod1
clrscr:
    xor dx,dx
    mov ah,02h
    int 10h
    mov bl,0000111b
    mov cx,25*80
    mov ax,0920h
    int 10h
    ret
    endp
aa1:
    mov dx,offset aaaa
    mov ah,9
    int 21h
    call mover
    mov dx,ax
    ret
    endp
bb1:
    mov dx,offset bbbb
    mov ah,9
    int 21h
    call mover
    ret
    endp

mover:
    mov dx,offset bufer
    mov ah,0ah
    int 21h
    mov dx,offset endstr
    mov ah,9
    int 21h

    xor di,di
    xor ax,ax
    mov cl,blength
    xor ch,ch
    xor bx,bx
    mov si,cx
    mov cl,10
tohex:
    mov bl,byte ptr bconteg[di]
    sub bl,'0'
    jb  tata
    cmp bl,9
    ja  tata
    mul cx
    add ax,bx
    inc di
    cmp di,si
    jb tohex
    jmp tra
tata:   jmp vvod1
tra:    ret
    endp

print:

    mov ebx,0ah
    xor cx,cx

divloop:
    xor edx,edx
    div ebx
    add edx,'0'
    push edx
    inc cx
    test eax,eax
    jnz divloop
restore:
    pop eax
    mov edx,eax
    mov ah,2
    int 21h
    dec cx
    cmp cx,0
    jne restore
    ret
    endp

endstrd:
    mov dx,offset endstr
    mov ah,9
    int 21h
    ret
    endp
ret
message1 db "PRESS",0dh,0ah
     db "+ for add. a+b.",0dh,0ah
     db "- for sub. a-b",0dh,0ah
     db "/ for div. a/b",0dh,0ah
     db "* for mul. a*b",0dh,0ah
     db "q for quit",0dh,0ah,'$'
message2 db "Press any key",0dh,0ah,'$'
aaaa     db "a=",'$'
bbbb     db "b=",'$'
endstr   db 0dh,0ah,'$'
enderes  db ' ',0dh,0ah,'$'
bufer    db 5
blength  db ?
bconteg:
hexstring equ bconteg
end start