The precision of the number

I have problem in Mathematica with unnecessary rounding which is caused by high precision. For example I have value a = 2.052685846*10^-1865, when I make b = 1 - a the result is b == 1.
What can I do to have a better precision, without rounding?

Answer

Works for me on Mathematica 8.0.
however, you can try using N to have the value number with the number of significant digits as you like:

b = N[ 1-a, 2000]

$2000$ digits after the decimal point in this case Mathematica does not perform rounding to $1$.

Comments

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