define variable

[electronicart]

Hi my friend....I want to define variable that is in HEX value & has 64 bits.but I dont know what I can use.....I use unsigned long long but it doesnt usefull.
can any one help me here?

[vlad from moscow]

Why is not unsigned long long usefull? And what do you mean by saying "in HEX value"?

[JLBorges]

#include <cstdint> // http://en.cppreference.com/w/cpp/header/cstdint

int main()
{
    std::uint64_t i = 0x123456789abcdef ; // unsigned integer type with exactly 64 bits (if available)
    std::uint_fast64_t j = 0x123456789abcdef ; // fastest unsigned unsigned integer type with at least 64 bits
    std::uint_least64_t k = 0x123456789abcdef ; // smallest unsigned unsigned integer type with at least 64 bits
    std::uintmax_t l = 0x123456789abcdef ; // unsigned integer type with the largest width
    decltype(0x123456789abcdef) m = 0 ; // integer type that can hold at least 0x123456789abcdef
}