Question

So I was doing some testing with the new data type long long when I stumbled upon a little “problem” (example came from C++ Primer 6th edition). I was using the climits library to tell me the maximum number supported by long and long long and both came out to 9223372036854775807. How is that possible?

#include <iostream> 
#include <climits>

int main()
{
    std::cout << "int size is " << sizeof(int) << " bytes." << std::endl;
    std::cout << "short size is " << sizeof(short) << " bytes." << std::endl;
    std::cout << "long size is " << sizeof(long) << " bytes." << std::endl;
    std::cout << "long long size is " << sizeof(long long) << " bytes." << std::endl;

    std::cout << "Maximum values: " << std::endl;
    std::cout << "int: " << INT_MAX << std::endl;
    std::cout << "short: " << SHRT_MAX << std::endl;
    std::cout << "long: " << LONG_MAX << std::endl;
    std::cout << "long long: " << LLONG_MAX << std::endl;

    return 0;
}

Answer 1

The C99 standard specifies ranges of values each type must be able to represent (§5.2.4.2.1). The specified values are minimum magnitude, so nothing prevent from having bigger range. I converted this value to the least number of bits needed to represent number in these ranges on a digital computer.

• int should be at least 16 bits (range from –32,768 to 32,767)
• long should be at least 32 bits (range from –2,147,483,648 to 2,147,483,647)
• long long should be at least 64 bits (range from –9,223,372,036,854,775,808 to 9,223,372,036,854,775,807)