DocumentationMathematicaBuilt-in FunctionsNumerical ComputationOptions
WorkingPrecision is an option for various numerical operations which specifies how many digits of precision should be maintained in internal computations.
WorkingPrecision is an option for such functions as NIntegrate and FindRoot.
Setting WorkingPrecision->n causes all internal computations to be done to at most n-digit precision.
Setting WorkingPrecision->MachinePrecision causes all internal computations to be done with machine numbers.
Even if internal computations are done to n-digit precision, the final results you get may have much lower precision.
See Section 3.9.3.
See also: AccuracyGoal, Precision, Accuracy, N.
New in Version 1; modified in 5.0.