This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.

Accuracy

 Accuracy[x]gives the effective number of digits to the right of the decimal point in the number x.
• Accuracy[x] gives a measure of the absolute uncertainty in the value of x.
• Accuracy[x] does not normally yield an integer result, and need not be positive.
• Numbers entered in the form are taken to have accuracy a.
• If x is not a number, Accuracy[x] gives the minimum value of Accuracy for all the numbers that appear in x. »
Machine-precision number:
Arbitrary-precision number:
Exact number:
Machine-precision number:
 Out[1]=

Arbitrary-precision number:
 Out[1]=

Exact number:
 Out[1]=
 Scope   (4)
Accuracy is the effective number of digits known to the right of the decimal point:
A zero known to accuracy 20:
The precision of is the same as the accuracy of :
Accuracy of a machine zero:
The uncertainty is effectively the smallest positive machine number:
Specify accuracy as the goal for N:
The accuracy of a symbolic expression is the minimum of the accuracies of its numbers:
 Applications   (2)
Check the quality of a result:
Track loss of accuracy in a repetitive calculation:
For machine-precision numbers, Accuracy[x] is the same as \$MachinePrecision-Log[10, Abs[x]]:
For non-machine numbers, Precision[x]==RealExponent[x]+Accuracy[x]:
Accuracy and Precision in iterating the logistic map: