Big Factorial program for the HP-15C

Description

This program computes the factorial of large numbers up to 1x10^8.

It computes the mantissa separately from the exponent. Enter the number to factorialize in the X register. Then press the A function key.
The value in the Y register is the Mantissa, and the value in the X register
is the exponent.

Program Resources

Labels

Name Description
 A Start the program

Storage Registers

Name Description
 0 The original number
 1 Stores the exponent

Program

Line Display Key Sequence Line Display Key Sequence Line Display Key Sequence
000 019 1 1 038 45 0 RCL 0
001 42.21.11 f LBL A 020 8 8 039 20 ×
002 44 0 STO 0 021 4 4 040 40 +
003 1 1 022 0 0 041 45 0 RCL 0
004 2 2 023 20 × 042 43 26 g π
005 20 × 024 1 1 043 20 ×
006 15 1/x 025 3 3 044 2 2
007 45 0 RCL 0 026 9 9 045 20 ×
008 43 11 g 027 34 x↔y 046 11 √x̅
009 2 2 028 10 ÷ 047 43 13 g LOG
010 8 8 029 30 048 40 +
011 8 8 030 1 1 049 44 1 STO 1
012 20 × 031 40 + 050 42 44 f FRAC
013 15 1/x 032 43 13 g LOG 051 13 10ˣ
014 40 + 033 45 0 RCL 0 052 42 31 f PSE
015 45 0 RCL 0 034 1 1 053 45 1 RCL 1
016 3 3 035 12 054 43 44 g INT
017 14 036 10 ÷ 055 43 32 g RTN
018 5 5 037 43 13 g LOG