How big can a 64bit signed integer be?

问题

In redis,

The range of values supported by HINCRBY is limited to 64 bit signed integers.

And I'd like to know how big can that 64 bit signed integer be.

回答1:

This article is good for more information about this topic: http://en.wikipedia.org/wiki/Integer_(computer_science)

So the answer to the question should be: From -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, or from −(2^63) to 2^63 − 1

The highest positive number stored in a signed int is represented binary as

----- 63 ones -----

0111111111111111111111111111111111111111111111111111111111111111

If you think carefully you can find out that this number is exactly 2^63 - 1.

回答2:

A signed integer ranges from size −2^(n−1) through 2^(n−1) − 1 so in this case the maximum value would be 2 ^ 63 - 1 or 9,223,372,036,854,775,807

回答3:

    Formula   

    2^(n-1) is the formula of the maximum value of a Bigint data type.

    In the preceding formula N is the size of the data type. The ^ operator calculates the power of the value.

    Now determine the value of N in Bit:

Select (max_length * 8) as 'Bit(s)' from sys.types Where name = 'BIGInt'
=64 Bits

Range:: -9223372036854775808 to 9223372036854775807

来源：https://stackoverflow.com/questions/6003492/how-big-can-a-64bit-signed-integer-be