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FACTORIAL PLUS by Daniel J. Bishop, April 2000   PUBLIC DOMAIN

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If you have used the TI-83's factorial operator (MATH/PRB/4), you may have noticed that you get an error message when trying to find the factorial of large numbers.  This is because the TI-83 cannot store numbers higher than 9.999999999e99.  Since 70! is greater than 10^100, you cannot calculate N! on the 83 when N >= 70.

Until now.

Factorial Plus can calculate the factorial of any integer.  All you need to do is copy the FCTORIAL.83P file onto your calculator, run it, and enter a value for N.

Examples:

N=?100            ; 100 is user input
100!=
9.332621544e157

N=?1000
1000!=
4.023872598e2567

Notice that there is a significant delay for 1000!.  Since execution time is proportional to N, it is not practical to use this program to find N! when N has more than four digits.  On the other hand, this is a vast improvement over not being able to find 70! (which, of course, is 1.197857167e100).

You can use this program as a subroutine in your own programs.  Just remove all the I/O statements.

prgmFACTORIAL
precondition:
     N=the number whose factorial you want to find
postconditions:
     M=the mantissa of N!
          (if N=1000, M=4.023872598)
     E=the exponent of N!
          (if N=1000, E=2567)
     F=base-10 log of N!
          (if N=1000, F=2567.604644)
other variables used:
     I=loop counter

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If you have any questions or comments, please e-mail me at danb2k@hotmail.com

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Other programs by Daniel J. Bishop at www.ticalc.org:

     The Algebra Toolkit v1.1  (freeware)
          location: 83\basic\math\algtool.zip
          Solves quadratic equations and sytems of 2 or 3 linear equations.  Graphs conic
          sections.  Finds area, side lengths, angle measures of oblique triangles.

     Bishop's Games Package  (public domain)
          location: 83\basic\games\games.zip
          Blackjack, craps, Day Trader, bricks, and tic-tac-toe.

     Day of the Week  (freeware)
          location: 83\basic\misc\dayofwk.zip
          On which day of the week was the most important event in your life?
          If you remember the date, you can use this program to find out.

     TI-83 Phone Book  (freeware)
          location: 83\basic\misc\phone.zip (?)
          Store the phone numbers of all your friends.

     SOLID Personal Organizer  (freeware)
          location: 83\basic\misc\solid.zip (?)  Not yet available.
          release date: 20 May 2000
          Successor to Phone Book allows longer names.  Also stores memos, displays monthly
          calendars, and converts between U.S. and metric units.

     The Statistics Toolkit v4.0  (freeware)
          location: 83\basic\math\stattk.zip
          Useful for AP Statistics students.  Includes univariate chi-squared test, normality
          test, Spearman's correlation coefficient, residual plots, and fake mem clear.

     VAPOR Personal Organizer  (public domain)
          location: 83\asm\misc\vapor.zip  ** DO NOT DOWNLOAD THIS FILE! **
          This program is being recalled because of an error message complaint.  It will be
          replaced by SOLID.          

     Weak Acid/Weak Base Solver  (freeware)
          location: 83\basic\science\acidbase.zip (?)
          finds the pH, pOH, [H+], [OH-], final acid concentration, and final base concentration
          of any weak acid/base solution if you know the Ka/Kb and initial concentrations.