How to convert String to Number in 8086 assembly?

Question

I have to build a Base Converter in 8086 assembly .

The user has to choose his based and then put a number, after then , the program will show him his number in 3 more bases[he bring a decimal number, and after this he will see his number in hex, oct, and bin.

This first question is, how can I convert the number he gave me, from string, to a number?

the sec question is, how can i convert? by RCR, and then adc some variable?

Here is my code:

data segment

  N=8

       ERROR_STRING_BASE DB ,10,13, "               THIS IS NOT A BASE!",10,13, "               TRY AGINE" ,10,13," $"     
        OPENSTRING DB "                      Welcome, to the Base    Convertor",10,13,"                     Please enter your base to convert     from:",10,13,"                   <'H'= Hex, 'D'=Dec, 'O'=oct, 'B'=bin>: $"

  Hex_string DB "(H)" ,10,13, "$"
  Octalic_string DB "(O) ",10,13, "$" 
  Binar_string DB "(B)",10,13, "$"
  Dece_string DB "(D)",10,13, "$"

  ENTER_STRING DB ,10,13, "      Now, Enter Your Number (Up to 4 digits) ",10,13, "$"
     Illegal_Number DB ,10,13, "      !!!  This number is illegal, lets Start     again" ,10,13,"$"


  BASED_BUFFER  DB N,?,N+1  DUP(0)  
  Number_buffer  db N, ? ,N+1 DUP(0)


  TheBase DB N DUP(0)                           
  The_numer DB N DUP(0)
  The_binNumber DB 16 DUP(0)
  data ends

   sseg segment stack
   dw   128  dup(0)
   sseg ends

    code segment
    assume ss:sseg,cs:code,ds:data

    start:  mov ax,data
    mov ds,ax


      MOV DX,OFFSET OPENSTRING ;PUTS THE OPENING SRTING 
      MOV AH,9
      INT 21H

    call EnterBase 

     CALL  CheckBase




     HEXBASE: CALL PRINTtheNUMBER 
     MOV DX,OFFSET Hex_string
     MOV AH,9
     INT 21h 
     JMP I_have_the_numberH 

     oCTALICbASE: CALL PRINTtheNUMBER 
     MOV DX,OFFSET Octalic_string 
     MOV AH,9
     INT 21h  
     JMP I_have_the_numberO          

     BINBASE:CALL PRINTtheNUMBER 
     MOV DX,OFFSET Binar_string
     MOV AH,9
     INT 21h  
     JMP I_have_the_numberB

     DECBASE: CALL PRINTtheNUMBER   
     MOV DX,OFFSET Dece_string
     MOV AH,9
     INT 21h 
     JMP I_have_the_numberD





    I_have_the_numberH: CALL BINcalculation
                CALL OCTcalculation
                CALL DECcalculation 




    I_have_the_numberO: CALL BINcalculation
                CALL DECcalculation
                CALL HEXcalculation


    I_have_the_numberB: CALL OCTcalculation
                CALL DECcalculation
                CALL HEXcalculation


    I_have_the_numberD: CALL BINcalculation
                CALL OCTcalculation
                CALL HEXcalculation


     exit:  mov ax, 4c00h
      int 21h  



     EnterBase PROC

     MOV DX,OFFSET BASED_BUFFER  ; GETS THE BASE 
     MOV AH,10
     INT 21H 


     LEA DX,BASED_BUFFER[2]
     MOV BL,BASED_BUFFER[1]
     MOV BH,0
     MOV BASED_BUFFER[BX+2],0

     LEA SI, BASED_BUFFER[2]
     XOR CX, CX
     MOV CL, BASED_BUFFER[1]

     LEA DI, TheBase

     LOL_OF_BASE:   MOV DL, [SI]
           MOV [DI], DL
           INC SI
           INC DI
           INC AL


        RET


       EnterBase  ENDP   



       CheckBase proc



       CMP  TheBase,'H' 
       JE HEXBASE

       CMP  TheBase,'h'
         JE HEXBASE


       CMP TheBase,'O'
        JE oCTALICbASE

       CMP TheBase,'o'
       JE oCTALICbASE

        CMP TheBase,'B'
         JE BINBASE 

         CMP TheBase,'b'
       JE BINBASE

        CMP TheBase,'D'
       JE DECBASE

        CMP TheBase,'d'
        JE DECBASE
        CMP TheBase, ' ' 
        je ERRORoFBASE 

      ERRORoFBASE: MOV DX,OFFSET  ERROR_STRING_BASE ;PUTS WORNG BASE Illegal_Number 
      MOV AH,9
      INT 21H 
      JMP START      



    CheckBase  ENDP




   PRINTtheNUMBER  PROC 


    MOV DX,OFFSET ENTER_STRING
     MOV AH,9
     INT 21h 


    MOV DX,OFFSET Number_buffer  ; GETS THE number
    MOV AH,10
    INT 21H 


     LEA DX,Number_buffer[2]
     MOV BL,Number_buffer[1]
     MOV BH,0
     MOV Number_buffer[BX+2],0

     LEA SI, Number_buffer[2]
     XOR CX, CX
     MOV CL, Number_buffer[1]

     LEA DI, The_numer 
     xor AL,AL

     LOL_OF_NUMBER_CHECK:   MOV DL, [SI]
                   MOV [DI], DL
                   INC SI
                   INC DI
                   INC AL 
                   CMP AL,5 
                   JE ERRORofNUMBER 
                   LOOP LOL_OF_NUMBER_CHECK 


    RET 

      ERRORofNUMBER: MOV DX,OFFSET  Illegal_Number ;PUTS WORNG BASE         Illegal_Number 
      MOV AH,9
      INT 21H 
      JMP START        

     PRINTtheNUMBER ENDP








      PROC BINcalculation  
          XOR CX,CX
          XOR AX,AX
          MOV CX,4
          MOV AX,16
          LEA SI, The_binNumber[0]
       TheBinarLoop: RCL  The_numer,1
          ADC [SI],0
          INC SI
          LOOP TheBinarLoop

      ENDP

      PROC OCTcalculation



      ENDP

      PROC DECcalculation

      ENDP

      PROC  HEXcalculation

      ENDP

     code  ends

     end start

It should be look like this:

thanks!

שלו לוי

Answer 1

the algorighm to decode ascii strings from ANY base to integer is the same:

result = 0
for each digit in ascii-string
   result *= base
   result += value(digit)

for { bin, oct, dec } value(digit) is ascii(digit)-ascii('0')
hex is a bit more complicated, you have to check if the value is 'a'-'f', and convert this to 10-15

converting integer to ascii(base x) is similar, you have to divide the value by base until it's 0, and add ascii representation of the remainder at the left

e.g. 87/8= 10, remainder 7 --> "7"
     10/8=  1, remainder 2 --> "27"
      1/8=  0, remainder 1 --> "127"

Answer 2

Copy-paste next little program in EMU8086 and run it : it will capture a number as string from keyboard, then convert it to numeric in BX. To store the number in "The_numer", you have to do mov The_numer, bl :

.stack 100h
;------------------------------------------
.data
;------------------------------------------
msj1   db 'Enter a number: $'
msj2   db 13,10,'Number has been converted',13,10,13,10,'$'
string db 5 ;MAX NUMBER OF CHARACTERS ALLOWED (4).
       db ? ;NUMBER OF CHARACTERS ENTERED BY USER.
       db 5 dup (?) ;CHARACTERS ENTERED BY USER. 
;------------------------------------------
.code          
;INITIALIZE DATA SEGMENT.
  mov  ax, @data
  mov  ds, ax
;------------------------------------------        
;DISPLAY MESSAGE.
  mov  ah, 9
  mov  dx, offset msj1
  int  21h
;------------------------------------------
;CAPTURE CHARACTERS (THE NUMBER).
  mov  ah, 0Ah
  mov  dx, offset string
  int  21h
;------------------------------------------
  call string2number
;------------------------------------------        
;DISPLAY MESSAGE.
  mov  ah, 9
  mov  dx, offset msj2
  int  21h
;------------------------------------------
;STOP UNTIL USER PRESS ANY KEY.
  mov  ah,7
  int  21h
;------------------------------------------
;FINISH THE PROGRAM PROPERLY.
  mov  ax, 4c00h
  int  21h           
;------------------------------------------
;CONVERT STRING TO NUMBER IN BX.
proc string2number         
;MAKE SI TO POINT TO THE LEAST SIGNIFICANT DIGIT.
  mov  si, offset string + 1 ;<================================ YOU CHANGE THIS VARIABLE.
  mov  cl, [ si ] ;NUMBER OF CHARACTERS ENTERED.                                         
  mov  ch, 0 ;CLEAR CH, NOW CX==CL.
  add  si, cx ;NOW SI POINTS TO LEAST SIGNIFICANT DIGIT.
;CONVERT STRING.
  mov  bx, 0
  mov  bp, 1 ;MULTIPLE OF 10 TO MULTIPLY EVERY DIGIT.
repeat:         
;CONVERT CHARACTER.                    
  mov  al, [ si ] ;CHARACTER TO PROCESS.
  sub  al, 48 ;CONVERT ASCII CHARACTER TO DIGIT.
  mov  ah, 0 ;CLEAR AH, NOW AX==AL.
  mul  bp ;AX*BP = DX:AX.
  add  bx,ax ;ADD RESULT TO BX. 
;INCREASE MULTIPLE OF 10 (1, 10, 100...).
  mov  ax, bp
  mov  bp, 10
  mul  bp ;AX*10 = DX:AX.
  mov  bp, ax ;NEW MULTIPLE OF 10.  
;CHECK IF WE HAVE FINISHED.
  dec  si ;NEXT DIGIT TO PROCESS.
  loop repeat ;COUNTER CX-1, IF NOT ZERO, REPEAT.

  ret 
endp    

The proc you need is string2number. Pay attention inside the proc : it uses a variable named "string", you have to change it by the name of your own variable. After the call the result is in BX: if the number is less than 256, you can use the number in BL.

By the way, the string is ALWAYS converted to a DECIMAL number.