Question about HP 41CX Memory Allocation

[EdFab]

I believe I have a fully functional HP 41CX but there is something I don't understand about memory allocation. I've been reading the online instruction manual for the HP 41C, and it says that the SIZE function will prompt for a 3-digit number between 000 & 318. Since the HP 41C comes with 63 registers, I'm assuming that the 318 limit only realistically applies if extended memory modules are installed. Please correct me if I'm wrong about this assumption.

After doing a memory clear on my HP 41CX, I did a shift->GTO .., and got "00 REG 219" in the display. I interpret this to mean that there are 100 data storage registers allocated, with 219 registers available for programming.

However, I have an X Memory module installed (I believe it's a double X Memory module at that, since CATALOG 4 gives me 600 in the display).

So my question is: Is it possible to allocate some of the registers on the X Memory module for data allocation? Could I enter SIZE 400 for example? (I'm guessing I can't based on the display of 00 REG 219 mentioned earlier when I pressed GTO .. with the X memory module installed).

Incidentally, I get the display of 00 REG 219 whether the X Memory is installed or not. So how does the X Memory module come into play at all?

I'm pretty clueless about this, I admit.

[Les Bell]

(09-06-2014 05:44 AM)EdFab Wrote:  Incidentally, I get the display of 00 REG 219 whether the X Memory is installed or not. So how does the X Memory module come into play at all?

The idea you're missing is that Memory and Extended Memory are two different things.

The SIZE command re-allocates main memory, which is shared between memory registers and program storage (plus key assignments and alarms, but let's not make it too confusing). A 41CX has 319 registers of memory.

Extended Memory, on the other hand, is devoted to files. A 41CX has 124 registers of extended memory, and it appears that you have a double Extended Memory module, which brings your calc up to the maximum of 600 registers of X-MEM.

The two cannot be merged or traded off. Rather, you can save programs (SAVEP), blocks of registers (SAVER, SAVERX) or the current X register value (SAVEX) to a named file (the file name is usually in the ALPHA register) and you can retrieve them using GETP, GETR, GETRX and similar commands. Data files are created using the CRFLD command.

So, think of X-MEM as being file storage, and you'll have the right idea. You really need to get a manual, perhaps on the Museum DVD.

[Joe Horn]

EDIT: Oops, Les beat me to an answer. Oh well, I hope something in the following is useful. -jkh-

(09-06-2014 05:44 AM)EdFab Wrote:  I believe I have a fully functional HP 41CX but there is something I don't understand about memory allocation. I've been reading the online instruction manual for the HP 41C, and it says that the SIZE function will prompt for a 3-digit number between 000 & 318. Since the HP 41C comes with 63 registers, I'm assuming that the 318 limit only realistically applies if extended memory modules are installed. Please correct me if I'm wrong about this assumption.

No, extended memory modules do not expand regular memory, they only expand "extended memory" which is different from main memory. A useful analogy is to think of extended memory as a tiny built-in disk drive, which you can store stuff onto, and recall stuff from, but which doesn't increase your main RAM.

(09-06-2014 05:44 AM)EdFab Wrote:  After doing a memory clear on my HP 41CX, I did a shift->GTO .., and got "00 REG 219" in the display. I interpret this to mean that there are 100 data storage registers allocated, with 219 registers available for programming.

Yep.

(09-06-2014 05:44 AM)EdFab Wrote:  However, I have an X Memory module installed (I believe it's a double X Memory module at that, since CATALOG 4 gives me 600 in the display).

Yes, it's a dual X memory module.

(09-06-2014 05:44 AM)EdFab Wrote:  So my question is: Is it possible to allocate some of the registers on the X Memory module for data allocation? Could I enter SIZE 400 for example?

No.

(09-06-2014 05:44 AM)EdFab Wrote:  Incidentally, I get the display of 00 REG 219 whether the X Memory is installed or not. So how does the X Memory module come into play at all?

Read Section 13 (pages 204-227) in the 41 CX Owner's Manual, and Appendix E (pages 370-373) and the table of Extended Memory Functions (pages 425-428). Then you'll be an expert at using extended memory.

[Garth Wilson]

(09-06-2014 06:40 AM)Les Bell Wrote:  The two cannot be merged or traded off. Rather, you can save programs (SAVEP), blocks of registers (SAVER, SAVERX) or the current X register value (SAVEX) to a named file (the file name is usually in the ALPHA register) and you can retrieve them using GETP, GETR, GETRX and similar commands. Data files are created using the CRFLD command.

Note there are also ASCII files (which I use a lot). I wish it had key-assignment files like the 71 has. Are there any modules that create and handle other types?

[Geoff Quickfall]

One of the modules ccd? Has a key assignment ability which is stored in extended memory. I have to do some research as I have a 'keya' file in extended right now but have forgotten how to recall it.

Geoff

[Sylvain Cote]

(09-06-2014 03:29 PM)Geoff Quickfall Wrote:  One of the modules ccd? Has a key assignment ability which is stored in extended memory. I have to do some research as I have a 'keya' file in extended right now but have forgotten how to recall it.

Geoff

Yep! you got a very good memory.
CCD Manual, Chapter 8
p8: [alpha] "KEYS" [alpha] SAVEK (save keys to specified extended memory file)
p9: [alpha] "KEYS" [alpha] GETK (get keys from the specified extended memory file)
p12: [alpha] "KEYS" [alpha] MRGK (merge keys from the specified extended memory file)

Sylvain

[Geoff Quickfall]

That's it!

Thanks Sylvain.

I have gotten lazy thanks to my two CLs. They remember everything in RAM including the entire calculator state.

Geoff

[EdFab]

Thank you for all the replies...yes, thinking of the X Memory module as a built-in drive for storage helps me visualize the concept.