/* The below code does not do input validation. It assumes the input string is a sequence of numbers */

ReallyBigRegister D;
char c;
char EOL = 0x0D;
char Subtract1 = 0x30;
char Subtract2 = 0x37; // Might require some fine-tuning

Start:

For each character in String
c = String[x];
   If c =/= EOL        // Check if character is end of line
        If c > 39
           c = c-Subtract1;
           Goto Shift
        Else
           c = c-Subtract2;
   Else


Shift:

D=(D<<4)|c;
//Could also use (D<<4)+c;
Goto Start