It depends on wether your compiler is ansi complient or not but you should have one or all of the following sprintf,fprintf,itoa. which can do the job.the most usefull routine ,itoa,looks something like this:-

/*-------------------------------------------------------------------------
 integer to string conversion

 Written by:   Bela Torok, 1999
               bela.torok@kssg.ch
 usage:

 _ultoa(unsigned long value, char* string, int radix)
 _ltoa(long value, char* string, int radix)

 value  ->  Number to be converted
 string ->  Result
 radix  ->  Base of value (e.g.: 2 for binary, 10 for decimal, 16 for hex)
---------------------------------------------------------------------------*/

#define NUMBER_OF_DIGITS 32

void _ultoa(unsigned long value, char* string, unsigned char radix)
{
unsigned char index;
char buffer[NUMBER_OF_DIGITS];  /* space for NUMBER_OF_DIGITS + '\0' */

  index = NUMBER_OF_DIGITS;

  do {
    buffer[--index] = '0' + (value % radix);
    if ( buffer[index] > '9') buffer[index] += 'A' - '9' - 1;
    value /= radix;
  } while (value != 0);

  do {
    *string++ = buffer[index++];
  } while ( index < NUMBER_OF_DIGITS );

  *string = 0;  /* string terminator */
}

void _ltoa(long value, char* string, unsigned char radix)
{
  if (value < 0 && radix == 10) {
    *string++ = '-';
    value = -value;
  }
  _ultoa(value, string, radix);
}