Depending on your architecture, the size of double is around 64 bits, this means it can hold a value of 2^64 which comes no where near your claimed value consisting of 308 digits.

The claimed article confirms thisNow with signed/unsigned in mind, you need to know that one bit is used as the signed bit which in total gives it a max value of +/- 2^63

when considdering it as signed.

Like Pam said, double is a floating point data type, meaning it is designed to ease floating point arithmetic, not meaning giving more storage space for your integer calculations.

In my mind "

*Teaching yourself <anything> in 21 days*" isn't the best learning experience, I would considder using a real book, like Osborne "

*The complete C++ Reference*"

And do keep in mind, C++ is

Teaching yourself programming in 10 years
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