HP48  for beginners!  www.geocities.com/~hpfb

FAQ's - Frequently Asking Questions

101- HP48 solves the factorial of 1.25.
What do this mean?
Factorial of negative numbers is not defined.
It returns the this number the Gamma Function of it
according to the formula: 

X! = Gama (X+1) if X > -1

For 1.25 for example it returns 1.13300309632
The factorial function "!" is equivalent to FACT

102-Do the HP48 have any hidden battery 
to maintain the memory while we replace the batteries?
HP48 there are not an hidden battery
See a photo of an opened HP48 in the address below.
http://www.geocities.com/~hpfb/ephoto.html

in order to keep memory working while we change batts
there is a capacitor of 1000 microfarads x 6.3 volts.
It can keep memory for a short interval of time, however
I have seen many calculators that keep the memory for hours
even without batteries.



103-What does the division of two matrices mean?

Division of matrices is not mathematically defined.
HP48 simply permits you multiply a matrix for its inverse using 
a shotcut, i.e. the key "[/]" instead of [1/x] [SWAP] [*].

>I put on the stack the following matrixes:

> [[2 3] [5 6]]
> 
> [[ 2 5] [ 5 7]]
> 
> and I pressed the key [/] and I saw
 
> [[ 1.818181818]
>  [ .2727272727]]

Indeed it returns this 2x2 matrix:

> [[ 1.818181818]
>  [ .2727272727]]

This is the same you get if you press [1/x] [SWAP] [*].
Remember that matrix multiplication is not commutative.

104-How can I make my own serial cable?

There are some pages where you can learn how to make your own cable:

1-
HP48 for beginners! Home Page brings a photographic version

http://www.geocities.com/~hpfb/makeacable.html
with many photos and explanations.

2-
https://members.tripod.com/~area48
Page of HP48 FAQs in Portuguese.
In FAQs there are a section that help to make a cable.

The English and Spanish version of FAQs are also available.

105-What is the external drive for HP48?

External drive or Drive 95, to be accurate is a drive for HP48 made
by DaVinci Technologies (former Sparcom).
It is a drive for 3,5 inches floppies that permits transfer files
directly from HP to a floppy.
It is available at www.sparcom.com

106-Where to find Brasil Disks?

The Brasil Disks is a collectanea of programs for HP48 made by brazilians.
It contains programs of many brazilians authors and the translation of FAQs,
of André Schoorl. They are two and the second volume was launched in january 1999.

You can find it at:

http://geocities.com/~hpfb/brdisks.html

http://hello.to/hpclub
Click on the link BRASIL DISKS

107-What is the Coma Mode? 

Pressing [ON] [SPC] the HP48 enters in the Coma Mode.
In coma mode it spent a minimum of energy, and this become possible save energy.
You can use the coma mode if you are traveling for example and batts are low.
During the coma mode the clock is turned off, so you need adjust it when turn on the calculator.
Press [ON], i.e. turn the calculator on, to exit the coma mode.

108-Where can I buy RAM cards ?

There are some known shops :

http://www.cynox.de (Germany)

http://www.sparcom.com (USA)

Remember that the brand of cards recommended to HP48 is the 
brand HP, made by EPSON.
However, I have a CYNOX RAM card and I never noticed any problem
since I am using it.

109-Does it worth to open the HP48?  
How you know to open HP48 to try some upgrade is highly NOT recommended.
Some people opened their HP48 when it stopped working.
Read below the story of some opening process.


from Alexandre Silveira Soares

Well, I opened, or best, I broken an HP48GX, of a friend whose LCD
was already broken.

I opened it, it damaged a lot, but I was able to close it
and glue it.
I think that if it is still working it didn't worth.
You can open, and if you can't close it, you can, at least,
make a little robot, for fun.

from Carlos Marangon

I opened both calculators and as I can see I just can use it
to satisfy my curiosity and study some components or to photograph
and make some tests with pins of cables.

from Tacio Philip Sansonovski

I opened an HP48G damaged that bought from a friend.
Clog locks it and when you open it is impossible to 
return the original way.

See photos of HP48 opened at hpfb Photo Gallery