Number input routine

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me239

Joined: 06 Jan 2011
Posts: 200

me239 19 Jul 2011, 06:27

Hey guys, I was wondering if anyone had any routines for accepting input from the cli that converts the number entered into a WORD value.

19 Jul 2011, 06:27

AsmGuru62

Joined: 28 Jan 2004
Posts: 1671
Location: Toronto, Canada

AsmGuru62 19 Jul 2011, 11:09

Get the text from user using INT 21H (AH=0Ah).
Then convert received text into a number using following pseudo-code:

Code:

RESULT=0

repeat until no more digits left within input text
    AL = load next digit
        SUB AL,'0'
        RESULT = 10*RESULT + AL
end repeat

Here http://www.codexxi.com/MyTools.html#atFASMW I have some code like this in a sample project for IDE. Look in PROJECTS folder - IntCalc sub-folder.

19 Jul 2011, 11:09

me239

Joined: 06 Jan 2011
Posts: 200

me239 20 Jul 2011, 00:55

AsmGuru62 wrote:

Get the text from user using INT 21H (AH=0Ah).
Then convert received text into a number using following pseudo-code:
Code:
RESULT=0

repeat until no more digits left within input text
      AL = load next digit
        SUB AL,'0'
        RESULT = 10*RESULT + AL
end repeat
    
Here http://www.codexxi.com/MyTools.html#atFASMW I have some code like this in a sample project for IDE. Look in PROJECTS folder - IntCalc sub-folder.

Can you explain what's wrong?

Code:

mov word[num], 0
    mov si, msg
    mov cx, 5
@@:
    lodsb
    mov ah, 0
    xchg ax, bx
    mov ax, [num]
    mov dx, 10
    mul dx
    add ax, bx
    mov word[num], ax
    loop @b
    mov ax, [num]
    int 20h   
num dw  0
msg db  '1234', 0

20 Jul 2011, 00:55

LocoDelAssembly
Your code has a bug

Joined: 06 May 2005
Posts: 4624
Location: Argentina

LocoDelAssembly 20 Jul 2011, 02:13

You forgot to subtract '0' (48). You use "sub bx, '0'" just before "add ax, bx" to fix this. Also note that you are setting up CX wrong, it should be 4 for your example to work properly.

20 Jul 2011, 02:13

me239

Joined: 06 Jan 2011
Posts: 200

me239 20 Jul 2011, 03:10

LocoDelAssembly wrote:

You forgot to subtract '0' (4. You use "sub bx, '0'" just before "add ax, bx" to fix this. Also note that you are setting up CX wrong, it should be 4 for your example to work properly.

Thanks! I got it now. Here is my whole routine

Code:

org 100h
start:
    mov word[num], 0
    mov si, msg 
@@:     
    lodsb
    cmp al, 0
    jz  @f
    mov ah, 0  
    sub al, 30h
    xchg ax, bx
    mov ax, [num]
    mov dx, 10
    mul dx
    add ax, bx
    mov word[num], ax  
    jmp @b   
@@:    
    mov ax, [num]  
num dw  0
msg db  '1234', 0

20 Jul 2011, 03:10

bitshifter

Joined: 04 Dec 2007
Posts: 796
Location: Massachusetts, USA

bitshifter 20 Jul 2011, 03:53

I hope something more goes here ...

Code:

mov ax, [num]   
...
num dw  0

20 Jul 2011, 03:53

me239

Joined: 06 Jan 2011
Posts: 200

me239 20 Jul 2011, 04:20

bitshifter wrote:

I hope something more goes here ...
Code:
mov ax, [num]   
...
num dw  0
    

actually it's a RET

20 Jul 2011, 04:20

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