jmp start
;****************************
;* Program to read in two   *
;* numbers and add them     *
;* and print out the result *
;****************************
  number db 7 dup 0             ; string which will store input and output
  n1     dw 0                   ; two input variables
  n2     dw 0
  res    dw 0                   ; one output variable
  cr     dw 13,10,"$"           ; carriage return, line feed
start:
  mov dx,number
  mov bx,dx
  mov b[bx],5                   ; maximum 5 characters to read
  mov ah,0ah
  int 21h                       ; read in a string from keyboard
  mov bx,number +1
  mov cx,00
  mov cl,[bx]                   ; cl now contains number of digits
  mov ax,00                     ; ax will contain the number input
  usedigit:
    inc bx                      ; get next digit
    shl ax,1                    ; multiply by 10 using 2 shift ops and an add...
    mov dx,ax                   ; ... x*8 + x*2 = x*10 is the principle.
    shl ax,2
    add ax,dx                   ; ax is now multiplied by 10
    mov dx,00
    mov dl,[bx]                 ; dl has new character
    sub dx,48                   ; subtract 48 = ascii('0') to get number value
    add ax,dx                   ; add to ax
  loop usedigit                 ; loop statement= jmp if cx > 0
  cmp n1,00                     ; see if this is first or second number read
  jnz second
  mov n1,ax                     ; assign it to the first variable
  jmp start                     ; read in another number
second:
  mov n2,ax                     ; or assign to second variable and continue
print_cr:
  mov ah,09
  mov dx,cr              ; print out a carriage return character
  int 21h
addnos:
  mov ax,n1                     ; move numbers to registers ...
  mov bx,n2
  add ax,bx                     ; ...and add
  mov res,ax                    ; store the result
  mov cx,00
setup_string:
  mov bx,number+7        ; put a $ at end of buffer.
  mov b[bx],'$'                 ; we will fill buffer from back forwards
  dec bx
  mov ax,res
convert_decimal:
  mov dx,10
  div dl                        ; divide by 10
  add ah,48                     ; convert remainder to character
  mov [bx],ah                   ; and move to buffer for output
  dec bx
  mov ah,00                     ; quotient becomes new value
  cmp ax,00                     ; if we haven't got all digits divide again
  jnz convert_decimal
printout:
  mov dx,bx
  inc dx                        ; we decremented once too many, go forward one.
  mov ah,09
  int 21h                       ; output the string
close:
  mov ah,4ch
  mov al,00
  int 21h                       ; end program