Need some 41CX, Quick Start Answers


I was reviewing some catalog functions and was wondering what the distinction was between function names. Some are just names and others begin with the raised 'T'. What is the distinction between these two function name types?

Also, I was testing the File Editor and am confused. I reset all memory. So I have 219 registers for program space and 100 registers for data.

I know that as I create programs the program space decreases and is noted by a reduction of the 219 to some lower value as the program grows.

But when I created a 10 register Text file, I don't see the program space decrease; don't see the register space decrease; don't see any of the data in the text file anywhere in the data registers.

So, where is this text data actually kept. If it is program space, why does the program space not show that it has been reduced by 10 registers?

Lastly, what is the largest memory configuration for the 41CX, including all external memory?


Text files are created in extended memory. The max extended memory (with two extended memory modules) is 600 registers. The main memory is 319 registers.

As for "external" memory - since the 41C can access floppies, tapes and PCs, I guess "unlimited" is the best answer.


Well maybe I'm missing something here. I have a 41CX with NO ext memory modules. In fact, there are no modules plugged in at all.

I still show 219 program registers and 100 data registers after I create a 10 register text file. I created the text file and entered the alphabet as text. Then went back and looked at program space and register space. Maybe the wrong test?

Where is the extended memory? Or does the 41CX come with extended memory in addition to 319 main memory? Like I said, I have NO external modules installed.


I found a command on the 41CX (EMROOM) that shows there is already extended memory. Didn't know that. Guess I need a manual:-)


The "functions with the "T" are programs, which have a "global" label such as 'MYPROG.

The built in functions appear without the "T", for example SIN.

If you would like to write a program that calculates the sine of an angle, it would like as:

01 LBL 'SIN ....... global name that gives the program its name

02 SIN ............ calls the SIN function which actually does the work

03 END ............ ends the program

If you enter this program, when you press the SIN key you will call the built in SIN function, but if you press XEQ SIN, the calculator will search first for a program with that name, and execute the program. If no program is found, then the search will look for a built in function and execute it if one is found.

Usually you will not create such trivial programs that add nothing to built in functions, and also will not name any program with a function name; this example is based on a atypical case on purpose.

I hope it may be of help for you.


How much memory is an interesting question.

The HP41 architecture seperates RAM and ROM into different address spaces. In fact the different address spaces even have different word sizes!

8 bit bytes in RAM and 10 bit bytes in ROM.

The RAM address space is 1024 registers, but because of the requirement for gaps in certain areas, the practical maximum would be less.

The status registers take up 16 registers (T, Z, Y, X, L, M, N, O, P, Q, |-, a, b, c, d, e).

Then comes 64 registers for a C or 320 registers for a CV or CX.

Then there's a gap

Then at a fixed memory address the first there's 128 (not exactly sure of this) registers of Extended memory for the Extended functions module (internal on the CX)

With each additional extended mem module you add a further 238 registers of extended memory.

So the fully expanded RAM is 16 + 320 + 128 + 238 + 238 registers (a total of 940 registers or 7520 bytes)

Note also that some peripherals appear to have memory mapped to them. The card reader in early versions would corrupt extended memory when you executed some of the 7xxxx functions. I'm not sure if this reflects some use of RAM, or some sloppy coding.

ROM is another matter. The HP41 has 16 pages of 4K. This is a total of 64K, but there are some tricks...

Firstly the first 3 (?) pages are the HP41 Operating system.

One page is reserved for a diagnostic ROM

One page is pretty much reserved for the printer.

That leaves 11 pages.

But you can only have 4 modules plugged in! Some modules are actually double (i.e. they are 8K). In addition Port extenders were made by 3rd parties that allowed you to have more ports) Also some brave souls broke open their modules and fitted more than one inside each case (I have a X-FN + 2 x EM in one case).

But there's more. With the CX, HP demonstrated that it is possible to bank switch the HP41 ROM. Some additional ROM hides at the same address as the printer (from memory)

Some clever soul determined that it was possible to bank switch any bank, so it would be possible to address 128K of ROM (however bank switching the HP41 OS would be rather dangerous)

So In RAM, your CX has about 3.6 Kb and probably around 20K of ROM. With 4 ROM modules you would add between 16 and 32Kb to that.

And does anyone know if it was possible to do 4 way bank switching -- I seem to remember something about that????

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