Why so much difference in output of visual c++ and mingw

In other words
MAC address: "XY-XX-XX-XX-XX-XX" "X" can be anything hexadecimal. The hexadecimal "Y", written in binary format, is Y: "kmnp", where "p" is the least significant bit;

        p=0 --> unicast; 
        p=1 --> multicast; 
        n=0 --> globally assigned MAC; 
        n=1 --> locally administered; 
So, actually MAC can be changed to any combination in which p=0 and n=1;

"Y" can be 2, 6, A or E.

So the possible MAC addresses in Windows 7 for wireless adapters:

#include <stdio.h>
#include <string.h>
#include <string>
#include <cmath>
#include <cassert>
#include <limits>
#include <stdexcept>
#include <cctype>
#include <iostream>

using std::cout;
using std::endl;

static const int CHARS= 57;	

static const char b64_table[65] = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

static const char reverse_table[128] = {
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64,
   64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 64, 62, 64, 64, 64, 63,
   52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 64, 64, 64, 64, 64, 64,
   64,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
   15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 64, 64, 64, 64, 64,
   64, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
   41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 64, 64, 64, 64, 64
};

std::string base64_encode(const ::std::string &bindata)
{
   using ::std::string;
   using ::std::numeric_limits;

   if (bindata.size() > (numeric_limits<string::size_type>::max() / 4u) * 3u) {
      throw ::std::length_error("Converting too large a string to base64.");
   }

   const ::std::size_t binlen = bindata.size();
   // Use = signs so the end is properly padded.
   string retval((((binlen + 2) / 3) * 4), '=');
   ::std::size_t outpos = 0;
   int bits_collected = 0;
   unsigned int accumulator = 0;
   const string::const_iterator binend = bindata.end();

   for (string::const_iterator i = bindata.begin(); i != binend; ++i) {
      accumulator = (accumulator << 8) | (*i & 0xffu);
      bits_collected += 8;
      while (bits_collected >= 6) {
         bits_collected -= 6;
         retval[outpos++] = b64_table[(accumulator >> bits_collected) & 0x3fu];
      }
   }
   if (bits_collected > 0) { // Any trailing bits that are missing.
      assert(bits_collected < 6);
      accumulator <<= 6 - bits_collected;
      retval[outpos++] = b64_table[accumulator & 0x3fu];
   }
   assert(outpos >= (retval.size() - 2));
   assert(outpos <= retval.size());
   return retval;
}

std::string base64_decode(const ::std::string &ascdata)
{
   using ::std::string;
   string retval;
   const string::const_iterator last = ascdata.end();
   int bits_collected = 0;
   unsigned int accumulator = 0;

   for (string::const_iterator i = ascdata.begin(); i != last; ++i) {
      const int c = *i;
      if (::std::isspace(c) || c == '=') {
         // Skip whitespace and padding. Be liberal in what you accept.
         continue;
      }
      if ((c > 127) || (c < 0) || (reverse_table[c] > 63)) {
         throw ::std::invalid_argument("This contains characters not legal in a base64 encoded string.");
      }
      accumulator = (accumulator << 6) | reverse_table[c];
      bits_collected += 6;
      if (bits_collected >= 8) {
         bits_collected -= 8;
         retval += (char)((accumulator >> bits_collected) & 0xffu);
      }
   }
   return retval;
}
struct upload_status 
{
  int lines_read;
};

char (*read_file())[CHARS]
{
	FILE* hFile=NULL;
	char (*fileBuf)[CHARS] =NULL;
	std::string fileName("Hello.txt");
	size_t fileSize,len(0);

	//opening the file
	hFile = fopen(fileName.c_str(),"rb");
	if (hFile == NULL)
		throw "File Does not exist.";

	//get file size
	fseek(hFile,0,SEEK_END);
	fileSize = ftell(hFile);
	fseek(hFile,0,SEEK_SET);

	//Checking file size
	if(fileSize > 1*1024)
	{}

	int no_of_rows = fileSize/54 + 1;
	fileBuf = new char[no_of_rows + 1][CHARS];	//Extra row for our special character to be used in conditional statements,here ""

	for (len=0 ; len < no_of_rows; ++len)
		fread(fileBuf[len],sizeof(char),54,hFile);

	strcpy(fileBuf[len],"");
	return fileBuf;
}

int main()
{
	char *data;
	char (*FEdata)[CHARS] = NULL;
	int len(1);
	struct upload_status upload_ctx;
	upload_ctx.lines_read = 0;
	std::string str,Estr("");
	FEdata = read_file();

	while (len)
	{
	  data = FEdata[upload_ctx.lines_read];
	  if(strcmp(data,"")) 
	  {
		size_t len = strlen(data);
		str = std::string(data);
		Estr += base64_encode(str);
		cout<<base64_encode(str);
		upload_ctx.lines_read++;
		continue;
	  }
	  len = 0;
	}
	cout<<"\n\n\n\n"<<base64_decode(Estr);
	return 0;
}