#include <stdlib.h>unsigned long long int strtoull(const char *start, char **end, int radix);
strtoull( ) was added by C99.
The strtoull( ) function is similar to strtoul( ) except that it returns an unsigned long long int. If the result cannot be represented as an unsigned long integer ULLONG_MAX is returned and the global variable errno is set to ERANGE. If start does not point to a number, no conversion takes place and zero is returned.
Related functions are strtol( ) and strtoul( ).