char* ultoa(unsigned long val, char *s, int radix)
The function ultoa() converts the unsigned long integer value from val into an ASCII representation that will be stored under s. The caller is responsible for providing sufficient storage in s.
The minimal size of the buffer s depends on the choice of radix. For example, if the radix is 2 (binary), you need to supply a buffer with a minimal length of 8 * sizeof (unsigned long int) + 1 characters, i.e. one character for each bit plus one for the string terminator. Using a larger radix will require a smaller minimal buffer size.
If the buffer is too small, you risk a buffer overflow.
radix as base, which may be a number between 2 (binary conversion) and up to 36. If radix is greater than 10, the next digit after '9' will be the letter 'a'.The ultoa() function returns the pointer passed as s.