Tento příklad dokáže převést číslo z jakékoliv číselné soustavy do císlové číselné soustavy
Po startu aplikace vyžaduje:

Číslo pro konverzi
Zdrojovou číselnou soustavu
Cílovou číselnou soustavu

#include "stdafx.h"
#include 
#include 
#include 
#include 
#include 
#include 
#include 


int Validate(char[], int, int);   
void ConvToDec(char[], int, int, int);  
void EvaluateWhole(long, int);
void EvaluateFract(double, int);
const int MAXSTRING = 30;

void main()
{
  char old_string[MAXSTRING];
  int original_base, new_base ;
 
  cout << "\nEnter number for conversion"
   << " (max-30 characters): " ;
  cin.getline(old_string, MAXSTRING, '\n') ;
  cout << "\nOriginal base (2-binary): " ;
  cin >> original_base ;
  if (!Validate(old_string, original_base, strlen(old_string)))
  cout << "\nNumber does not belong to specified base!" ;
  else
  {
  cout << "\nEnter number for conversion: " ;
  cin >> new_base ;
  ConvToDec(old_string, original_base, new_base, strlen(old_string));
  }
  getchar();
}

int Validate(char str[], int base, int length)
{
  int aski_val ;
  aski_val = '0' + base ;
  if (base>10)
  aski_val += ('A' - '9') -1;   
  for (int i=0; i  {
  if (str[i] >= aski_val)
  return 0;      
  }
  return 1;   
}

void ConvToDec(char str[], int base, int new_base, int length)
{
  double dec_frac =0;
  long dec_num =0;
  int dec_digit =0;
  for (int i=0; i  {
  dec_digit = str[i] - '0';
  if (str[i]>='A')
  dec_digit -= ('A' - '9') -1;   
  dec_num = dec_digit + dec_num*base;
  }
  EvaluateWhole(dec_num, new_base);
  int index;
  if (str[i] == '.')
  {
  for (index = --length ; index > i; index--)
  {
  dec_digit = str[index] - '0';
  if (str[index]>='A')
    dec_digit -= ('A' -'9') -1;  
  dec_frac = (dec_frac + dec_digit)/base;
  }
  EvaluateFract(dec_frac, new_base);
  }
}

void EvaluateWhole(long DecWhole, int base)
{
  char new_string[MAXSTRING] ;
  int i = 0, aski_val;
  while (DecWhole > 0)
  {
  aski_val = DecWhole % base + '0';
  if (DecWhole%base > 9)
  aski_val += ('A' - '9') -1;   
  new_string[i] = aski_val ;
  DecWhole = DecWhole/base ;
  i++;
  }
  cout << "\nThe number converted is " ;
  for (int j=i-1; j>=0; j--)
  cout << new_string[j] ;
}





void EvaluateFract(double DecFrac, int base)
{
  char FracDigit ;  
  int Digit ;
  cout << "." ;    
  for (int i=0; i<10; i++)   
  {
  DecFrac = DecFrac * base ;  
  Digit = (int)DecFrac ;
  DecFrac -= Digit;
  FracDigit =  Digit + '0' ;
  if (base>10 && FracDigit>'9')
  FracDigit += ('A' - '9' - 1) ;
  cout << FracDigit ;
  }
}