How to turn off GRAD on HP41C


WHat is and how to turn off the word GRAD on display on HP41C?


400 grads = 1 revolution (360 degrees). To switch out of that mode, press either:





--- Les Bell, CISSP


Thanks Les,

It works, GRAD disappeared. Do you know
how I could have gotten there? The key
strokes were nontrivial and I have never
use the grad/degree/rad functions ever.



deg/rad/grad angular modes are set by executing directly their "names", as in [XEQ] [ALPHA] DEG [ALPHA]. This key sequence will result in their respective functions - DEG, RAD or GRAD - and these functions mau be part of a program. The GRAD annunciator (and respective mode) may be set by a running program.

Hope it helps.

Best regards.


I have to check, but I think to remember that the DEG/RAD/GRAD modes can also be activated by flags (SF for Pat).

I'll have a look at the manual and confirm.


The corresponding Angular Mode Flags are 42 and 43; Set/Clear combinations of them result in any of the Angular Modes. Status at reset is clear/clear, which represents DEG (if I remember right). The remaining meanings of combinations (which I do not remember) are easily obtained by experiment (just try each of the combinations clear/clear, clear/set, set/clear, set/set for Flags 42/43) :-)



The only problem is that you can't control flags 42 and 43 using SF and CF.
You can do it with synthetic programming (of course), or by using one of the 3rd party modules that contains a flag control program that will work with any flag (the PPC ROM being the best known I think).


Well, yes, Tony, you're right, my oversight! However, is there any deeper reason why those flags - which are controlling a "user-function" after all - are not accessible for the user at all? I mean, you may set them indirectly by XEQ DEG, GRAD or RAD after all, so where's the reason that HP refused to operate on them directly? OK, you need 3 combinations for the 3 Angular Modes, whereas Flags 42,43 supply 4 combinations. So, I guess, the 4th combination is actually controlling a system state that's not supposed to be changed by the user?


Maybe the answer is that to control 3 modes, you need at least 2 bits...


Do you mean, HP intended to prevent confusion of the "average" user? Might well be. What about similar situations? E.g. Modes (SCI, ENG, FIX): they are controlled by more than 1 Flag and they are "user-functions" as well; I can't remember whether their respective Flags can be controlled by the user directly (by means of SF, CF) or not. However, if your guess is right, HP should have disabled direct control of these too ...


Flags between 0 and 10 are controlled only by the user, and have no meaning for the system.

Flags between 11 and 29 are controlled by the user with SF or CF and also by specific functions like [USER], [ALPHA]; and have meaning for the system such as selecting radix and digits grouping, enabling or disabling the beeper, error handling, writing private cards, , overwriting write protected cards, controlling printer modes, enabling Autorun (we could call it AUTOEXEC nowadays), etc.

Flags 30 to 55 are system flags, the user cannot set or clear them except by specific functions like FIX, SCI, ENG, DEG, RAD, GRAD, ON; and some combinations are not enabled or not documented. The user can test them with FS?, FC?; but in some cases the results will be meaningless.

Synthetic programming, and the Extended Functions STOFLAG, RCLFLAG and X<>F instructions allow for advanced flag manipulation; these are the usual ways to test "invalid" flags combinations. I did some experimenting some years ago, without any remarkable result.


Thanks for the summary of Flag control and manipulation, Andres! B.t.w., I liked espec. your comparison of Flag set{11,...,29} with AUTOEXEC :-) Intersesting point of view ...


If Flag 11 is set (if I recall correctly), when the calculator is turned on it will start running the program at the point it was when turned off (as if an automatic R/S have ocurred). That is why I mentioned Autoexec. Keep in mind that Flag 11 is tested and reset each time the calculator is turned on.

For instance, the following program is a fun example:


02 LBL 01

03 SF 11 ; Prepare for autoexec when turned on ...

04 OFF ; Turns itself OFF, waits HERE for someone to turn the calculator ON ...

05 GTO 01 ; Repeat as fast as possible!

06 END


I agree, FL11 used this way certainly is the most obvious that can be compared with AUTOEXEC as it AUTOmatically EXECutes the program you wish on turn on. On the other hand, as all Flags out of the remaining set {12,...,29} will put your calculator in a customized state, would it make sense to compare it with a nowadays_CONFIG.SYS?




If ResetSequence=True Then
End If


You see, no emm386, no himem, no UMB, no conflict.... That's the way (ha-ha ha-ha) we like it !


Whether added by a module or built into the 41CX:

X-Functions = "emm386".

Unfortunately, X-memory is more like a swap space than extended memory. 2.2 kB RAM can be constraining, as users of the 28C found out...


System flags, the ones related to SCI,FIX,ENG or DEG,GRAD and RAD can not be set directly but can be tested in user program so that the program could know which mode the calc is set.


If you have a 41CX, or a 41C/CV with an Extended Functions Module, a RCLFLAG operation may have caused GRAD to appear.


You have to handle Flag 42.
3 methods in order to turn "GRAD" off.
2- Using Synthetic Programming and working on "d" register.
3- Using a PPC ROM for instance: 42 XEQ ALPHA I F ALPHA.
Good luck!


[ for M
\ for N
] for O

01 LBL "IF"
02 ABS
03 24
04 +
05 STO [
06 8
07 ST/ [
08 MOD
09 RCL d
10 X<> [
11 INT
14 X<>Y
15 X<> ]
16 X<> \
17 X<> d
18 FC?C IND ]
19 SF IND ]
20 X<> d
21 STO [
22 RDN
23 12
24 -
27 X<> ]
28 STO d
29 RDN
30 CLA
31 RTN


IF you're using an interface (HP82164A RS232c or HP82169A HPIB/HPIL for instance) and HP82183A Extended I/O module, please INP a file (IF.BIN why not?)containing the following codes line:



Note that all that hex data must be one one line. There must be no spaces, newlines, etc in the middle of it. INP will complain if there are.
Is the format of the INP (and OUTP) data documented anywhere, or didyou figure it out the hard way like I did?


Please use Synthetic HP-41C QRC for SP in order to "understand" those curious hex codes:
49 I
46 F
61 ABS
12 2
14 4
40 +
91 STO
75 M
18 8
95 ST/
75 M
90 RCL
7E d
You use similar codes with program "LB" (Load Bytes).


I am well aware of the hex coding for HP41 Focal instructions. I've worked with it often enough, and my SP QRG (the 40 page booklet) is in front of me as I type.
The point is that INP and OUTP hex streams have (IIRC) the program length sent first (as 2 bytes / 4 hex characters) and a checksum on the end (1 byte, 2 hex characters). The exact format of that, and how the checksum is calculated, seems to be undocumented.
Before you ask, yes _I_ think I understand how it's done...


Thanks for the instructions ... they worked and the
GRAD annunicator is now gone.

I have one Financial and three Memory Modules installed
but they were not used. I had not run any other programs
so how did I got into this state remains a mystery. Glad
I am out of it. Thanks for all the help I received.


Was the USER indicator turned on ?

Maybe one of the keys were assigned to "GRAD"... I remember I did this in my trigs classes as some exercices were expressed in degrees and other in radians...


Good point!!


When we give a glance to our favourite claculator, really, aren't we impressed on how powerful it is ?


When we give a glance to our favourite claculator, really, aren't we impressed on how powerful it is ?

This machine has been developped to be USED rather than to be a technology showcase...



may I extend this "compliment" to all of them? At least, the "original HP equipment"? I myself posted this opinion more than one time in here, and it's good to know I'm not alone in my thoughts.

And let's also consider THE users: we see a thread in here were everyone shown his knowledge in a way all others agreed and kept adding suggestions, opinions, solutions, about a single angle mode. We know the machine can do it all, we know many of us know it all, and we feel fine reading and posting more and more info (as this bunch of words in here). For fun, pleasure, needing.

It's a pity (a shame?) the recent Hewlett-Packard Co. can no longer see or understand it all.

Good words. Good thread.


I love the early machines and all the capabilities packed into them. I have never been a power user and although I am old enough, I wasn't involved in the "heyday" when people were trying to figure out how to use them for the first time, when HP calculators represented as much computing power as an ordinary person could afford.

I want to give some credit to later computer companies, including HP, for the amount of computer power that is now available to ordinary users at an inexpensive price. I worked for a personal computer manufacturer and I know that all the emphasis was on making the machines easier for unskilled people to use so more people would buy them, and over time this has led to a great reduction in the entry price and a tremendous increase in the calculating power. (That so much of that power is being used to deliver pornographic images is beside the point!)

With the graphical user interface, preferences and online help, you don't so much figure out how to use the computer as tell it how to work. (I know this isn't true, but it's the company line, and like communism, it appears to be a beautiful dream that will never become reality.)

Well, I've always preferred trying to figure out how things work to actually using them. To me, "Plug and Play" is a cruel joke - what fun is there in that? I have an amatuer radio book from the 1930's or 40's (not the ARRL handbook, but a book for more general use). One chapter is about a facsimile system that was being tested at the time. Broadcast stations would transmit newspapers overnight, you wouldn't even have to step outside to get your paper in the morning. It was a graphical system that printed on electrosensitive paper. You would buy the printing unit and connect it to the output of your radio. A critical step in the project was wiring a switch to disconnect your radio's speaker, otherwise you would hear a terrible din all night! That's the kind of high technology I can get excited about!


You're welcome.
It was a pleasure.
Good luck!

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