How to convert string to number in Tasm?

Question

I made a program that reads a string and converts it into a number. A string representation of the number entered in the decimal system. The result of of converting is in re

Answer 1

You could, for example, extend your multiplication by 10 from 16 to 32 bits like this:

; file: mul32ten.asm
; compile: nasm.exe mul32ten.asm -f bin -o mul32ten.com

bits 16
org 0x100

    xor     dx, dx
    xor     ax, ax

    mov     si, MyStr

NextDigit:
    mov     bl, [si]
    or      bl, bl
    je      Done
    call    MulDxAxBy10
    sub     bl, '0'
    add     al, bl
    adc     ah, 0
    adc     dx, 0
    inc     si
    jmp     NextDigit

Done:
    ; dx:ax should be equal to 7FFFFFFF now
    ret

MulDxAxBy10:
    push    si
    push    di
    shld    dx, ax, 1
    shl     ax, 1       ; dx:ax = n * 2
    mov     si, ax
    mov     di, dx      ; di:si = n * 2
    shld    dx, ax, 2
    shl     ax, 2       ; dx:ax = n * 8
    add     ax, si
    adc     dx, di      ; dx:ax = n * 8 + n * 2 = n * (8 + 2) = n * 10
    pop     di
    pop     si
    ret

MyStr db "2147483647", 0