function adapted from assembly routine

Who said you can't do two things at once, or at least in the same day. With that in mind I started learning assembly.

I took this assembly language routine and converted it to c++ and just wanted to show it off for critiquing. Here is the asm code, then the c++.

note the assembly language routine comes from Jeff Duntemans book Assembly Language Step by Step

Code:

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Byte2Str:
    mov DI, AX                        ; Duplicate byte in DI
    and DI, 000FH                  ; Mask out high 12 bits of DI
    mov BX, Digits                  ; Load offset of digits into BX
    mov AH, BYTE [BX+DI]      ; Load digit from lookup table
    mov [SI+1], AH                  ; store digit into string
    xor AH, AH                        ; trick to zero out AH
    mov DI, AX                        ; move byte into DI
    shr DI,4                              ; Shift high nyble of bite to low
    mov AH, BYTE [BX+DI]        ; Load digit from digits table into string
    mov [SI], AH                      ; store digit into string
    ret

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The C++ with some adaptation

Code:

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// Hex2.cpp : Defines the entry point for the console application.

#include <iostream>
using std::cin;
using std::cout;
using std::endl;

#include <string>
using std::string;

#include <stdlib.h>

string byte_to_hexstring(short int);


int main(int argc, char* argv[])
{
        short int number;
       
        // fetch number must be short int
        cout << "Enter a number [0-255]: ";
        cin >> number;
    cout << endl;
   
        // display hexstring equivalent
        cout << "In hex : " << byte_to_hexstring(number);
        cout << endl;
       
        cin.ignore(1);
       
        system("PAUSE");
        return 0;
}

string byte_to_hexstring(short int decimal)
{
       
        string digits="0123456789abcdef";
        string hexstring="  ";

        int temp_digit=0;
        int mask=15;                                // bit mask to eliminate high order nybl
        temp_digit=decimal & mask;      // eliminate high order hex digit;
       
        hexstring[1]=digits[temp_digit];// use digits as look up table to refrence char
       
        temp_digit=decimal >> 4;        //move high order nyble first hexdigit to low order position
        hexstring[0]=digits[temp_digit];//first char of string equals highorder nyble of decimal

        return hexstring;
}

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