Example Program to calculate Factorial

[Csaba Tizedes]

... and HP-12C version in engineer style:

The core is 3 steps:

Code:

01: LN
02: \GS-
03: GTO 01

Preparation for use required to clear statistics registers, store your number (N) in R1, then goto the start of program memory, run the program and you'll get the -LN(N!) in R2.
You can get N! if you type

Code:

RCL 2
CHS
e^x

If you like waste some memory you can program it fully (9 steps):

Code:

01: STO 1
02: LN
03: \GS-
04: x=0
05: GTO 07
06: GTO 02
07: RCL 2
08: CHS
09: e^x

Use:
1.) f CLEAR \GS
2.) f CLEAR PRGM
3.) Type N
4.) R/S

Benchmark:
69! = 1.711224655E99, running time: 62 secs on "classic" 12C Made in Brazil (S/N: 3107B...)

Some hints are welcome to optimize the code (twisted GTO 07/02 really terrible)

Csaba