C++ Binär > Hex und andersrum

#include <math.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>

#define FirstDigit 48

void BinToHex(char* BinData, char* HexData)
{
   long int Number = 0;
   int BinLength = strlen(BinData);

   for(int i=0; i<BinLength; i++)
   {
      Number += ((BinData[BinLength - i - 1] - FirstDigit) * pow(2, i));
   }

   ltoa(Number, HexData, 16);
}

int main()
{
   char* BinBuffer = "11110101";
   char HexBuffer[256];

   BinToHex(BinBuffer, HexBuffer);
   printf("Bin: %s\nHex: %s", BinBuffer, HexBuffer);
   getch();
   return 0;
}