Big Pi
by Zeda Thomas

  This is a set of BASIC programs to calculate pi to arbitrary
precision.

How to use:
  Send all of the programs to your calculator

  On the homescreen, do something like:
    20:prgmBIGPI
  This computes PI to 20 digits (it outputs more, but those may be inaccurate).

  Read L1 as 5-digit chunks of the expansion of pi!
  The last chunk will probably be off in the last few digits.

  This takes can take a LONG time! It takes a few minutes to evaluate 100 digits.

Tweaks:
  If you open up BIGPI in the editor, you will see a line that
looks like:
    5->I

  This determines the size of the chunks of the digits. Increasing
this will speed up the calculation, but it can cause errors due
to floating-point precision. For example, using a size of 10
digits caused the result to be off after about 40 digits.
  I haven't tested it enough, but a value of 8 should be safe
while speeding up calculation by 60%. 9 *might* be safe, but I
don't know.