Conversion of character string to integer (unsigned long type) and storing pointer in last character string
unsigned long strtoul(const char *str, char **ptr, int base);
Returns the converted value if the partial character string could be converted. If it could not, 0 is returned.
If an overflow occurs, ULONG_MAX is returned, and macro ERANGE is set to global variable errno.
This function is the same as strtol except that the type of the return value is of unsigned long type.