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diff --git a/assignment4/sample_code_assignment4_decimal_digits.cpp b/assignment4/sample_code_assignment4_decimal_digits.cpp
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+////////////////   159201   ///////////////////////////////////
+//SAMPLE CODE FOR ASSIGNMENT 4 - Big Numbers
+//2012 
+#include <cstdlib>
+#include <iostream>
+#include <fstream>
+#include <locale>
+#include <sstream>
+#include <string>
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+using namespace std;
+
+/////// PART A
+
+//copy the template class List here
+
+
+/////// PART B
+class BigNumber {
+private:
+//complete here...
+//include here a List of integers, or shorts etc
+
+public:
+//complete here...
+//what methods do you need?  
+  BigNumber();
+  ~BigNumber();
+  void ReadFromString (string decstring );
+  void PrintBigNumber ();
+  void AddBigNumbers(BigNumber B1,BigNumber B2);
+};
+
+BigNumber::BigNumber(){
+// anything here?
+}
+
+BigNumber::~BigNumber(){
+//you can keep that empty
+}
+
+void BigNumber::ReadFromString (string decstring ) {
+  //cout<< "testing string passing: "<< decstring << endl;
+	//read a string, adding a new node per digit of the decimal string
+	// To translate 'digits' to integers: myinteger=decstring[index]-48
+	
+  for(int i = 0; i < decstring.size(); i++) {
+      int temp=decstring[i]-48;
+      cout << "Digit " << i << " is " << temp << endl;  //Comment this out for your final version
+      //You need to use the AddtoFront() 
+  }
+}
+
+void BigNumber::PrintBigNumber () {
+//complete here, print the list (i.e., use FirstItem() and NextItem() )
+//remember that the print out may be inverted, depending on the order you enter the 'digits'
+}
+
+void BigNumber::AddBigNumbers(BigNumber B1,BigNumber B2){
+//complete here.
+//use FirstItem(), NextItem() and AddNode()
+//to add two big numbers, what do you have to do? Be careful about the carry
+//Remember to add the last carry, the resulting number can have one more digit than B1 or B2
+}
+
+/////// PART C
+
+BigNumber B1,B2,RES;
+
+main (int argc, char ** argv) {
+  string numberstring;
+  int stringseq=0;
+  ifstream input_file;
+  if(argc==2) input_file.open(argv[1]);
+  else { cout<< "cannot read the file " << argv[1] << endl; exit(0);}
+  while(!input_file.eof()){
+    getline(input_file,numberstring);
+    if(!input_file.eof()){
+      cout << "reading a big number from file:" << numberstring << endl;//Comment this out for your final version
+      if(stringseq==0){
+        B1.ReadFromString(numberstring);
+        stringseq=1;
+      }
+      else B2.ReadFromString(numberstring);
+    }
+  }
+  //print
+  B1.PrintBigNumber();//PROBLEM: Is the printing inverted? How can you solve this problem? Before or after using AddBigNumbers()?
+  cout << "+" << endl;
+  B2.PrintBigNumber();
+  cout << "=" << endl;
+  //compute the addition
+  RES.AddBigNumbers(B1,B2);
+  //print the result
+  RES.PrintBigNumber();
+}