atof error

[sandodo]

Thanks Paul McKenzie for the helpful link.

1/3 cannot be represented by a decimal number, because 3 is not a divisor of 10.
Similarly, 1/5 cannot be represented by a binary float, because 5 is not a divisor of 2.

Numbers that can be represented by binary floats are sums of powers of two.
It's easy to see that these numbers can be expressed with this form:

integer*2**i where i is a negative or positive integer.

Thanks. the example of 1/3 cannot be represent by decimal number is very good.

However for

integer*2**i

, cannot understand......