This is documentation for Mathematica 3, which was
based on an earlier version of the Wolfram Language.
 SetPrecision SetPrecision[ expr , n ] yields a version of expr in which all numbers have been set to have a precision of n digits. When SetPrecision is used to increase the precision of a number, the number is padded with zeros. The zeros are taken to be in base 2. In base 10, the additional digits are usually not zero. SetPrecision returns an arbitrary-precision number, even if the precision requested is less than \$MachinePrecision. When expr contains machine-precision numbers, SetPrecision[ expr , n ] can give results which differ from one computer system to another. SetPrecision will first expose any hidden extra digits in the internal binary representation of a number, and only after these are exhausted add trailing zeros. 0.004`25 generates a number with all trailing digits zero and precision 25 on any computer system. SetPrecision[ expr , n ] does not modify expr itself. See the Mathematica book: Section 3.1.5. See also: N, Precision, Chop, SetAccuracy, \$MinPrecision, \$NumberMarks. Further Examples Here is a machine-precision real number approximation of 1/3. In[1]:= Out[1]= You can increase the precision to 40 digits. In[2]:= Out[2]= The additional digits are 0 in base 2, not in base 10. (Mathematica uses base 2 internally to represent numbers.) In[3]:= Out[3]//InputForm=