# Set Global Maximum Precision

I'm sure this has been asked before, but I've looked around and can't figure it out:

How do I set a global maximum precision for a notebook (or in general, globally)?

I have a large notebook in which I'm trying to get Mathematica to do all computations to a precision of 15 digits. The objective is to compare the results of the computation at the end with the default precision to the 15 I am enforcing. What are the options that I have to set at the beginning of the notebook to make this happen?

Thanks!

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Look up $MinPrecision and $MaxPrecision. –  Ｊ. Ｍ. Oct 30 '12 at 6:03
Bear in mind that Mathematica's concept of precision is rather different to that of e.g. Maple, and there is in fact no "default precision". Numbers in Mathematica are either machine precision (53 bits, no precision tracking) or arbitrary precision with a specified number of digits and significance arithmetic enabled. If you want to work at fixed precision you must use $MinPrecision =$MaxPrecision = prec and always use arbitrary-precision numbers (machine precision ones will poison the calculation, so avoid introducing them at all). –  Oleksandr R. Oct 30 '12 at 13:14