DM42 arrived today! Stack layout?

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48GX
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DM42 arrived today! Stack layout?

Post by 48GX » Wed May 27, 2020 10:54 pm

I currently have XYZT enabled.

What does XYZTL and XYZTA do? Just give an extra register on the stack? Why the difference in the last letters?

Please forgive me if this has been asked before. I’m on my phone and can’t find anything using search.

Love the 42!! Feels solid in the hand. Will probably order another one or two soon.
HP48GX since 1994
DM42 (2), HP42s, HP35s

rprosperi
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Re: DM42 arrived today! Stack layout?

Post by rprosperi » Wed May 27, 2020 10:59 pm

"L" is the LAST X register

"A" is the Alpha register

Alpha is obvious, but coming from RPL, the LAST X is likely not familiar. But it's actually just that, the last value that was in the X register before it's value was changed by the prior operation. Traditionally it was a bit difficult to learn what was there, unless you made some detailed stack diagrams, but since the DM42 let's you see it, it will quickly become obvious what's there, and why it's useful.
--bob p

DM42: β00071 & 00282, DM41X: β00071, DM10L: 071/100

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48GX
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Re: DM42 arrived today! Stack layout?

Post by 48GX » Thu May 28, 2020 12:21 am

Thank you, Bob. I appreciate the X description.

Coming from RPL has me completely turned around. I think the 42s stack is one area where without any doubt to me the 48G makes more sense.

What is the Alpha?

Also, if I do,

5 Enter 5 Enter 5 + + The 5s roll off the stack like I expect.

However, if I fill up XYZT with 5s, they don’t roll off (empty) the stack. Why is this? Why does the stack stay full of 5s?

I appreciate you answering my questions. I have a lot to learn.
HP48GX since 1994
DM42 (2), HP42s, HP35s

toml_12953
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Re: DM42 arrived today! Stack layout?

Post by toml_12953 » Thu May 28, 2020 12:52 am

48GX wrote:
Thu May 28, 2020 12:21 am
Thank you, Bob. I appreciate the X description.

Coming from RPL has me completely turned around. I think the 42s stack is one area where without any doubt to me the 48G makes more sense.

What is the Alpha?

Also, if I do,

5 Enter 5 Enter 5 + + The 5s roll off the stack like I expect.

However, if I fill up XYZT with 5s, they don’t roll off (empty) the stack. Why is this? Why does the stack stay full of 5s?

I appreciate you answering my questions. I have a lot to learn.
You really should read the HP-42S manual. It has all the information you need.
http://www.hp41.net/forum/fileshp41net/ ... 42s-us.pdf
Also, to get a fast course in RPN (as opposed to RPL) try here:
http://holyjoe.org/hp/RPN_tutorial.pdf
Tom L

I bought a moving blanket but it just sits there.

DM10L SN: 059/100
DM41X SN: 00023 (Beta)
DM42 SN: 00025 (Beta)
DM42 SN: 00221 (Shipping)

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48GX
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Re: DM42 arrived today! Stack layout?

Post by 48GX » Thu May 28, 2020 1:42 am

Hi toml_12953. Thank you for replying. I had already read through Joe's guide and have read through most of "An Alternative HP-42S/Free42 Manual". I have only skimmed the actual user manual but hope to start on it this weekend.

The Alpha Register seems to be the register that stores the last Alphanumeric entry. Easy enough but it wasn't really spelled out anywhere I could find in "An Alternative HP-42S/Free42 Manual".

I still don't understand the following.

Put a 5 in XYZT and then hit + the stack never changes. Same for filling it with 4 3 2 1 and 4 just falls but T never becomes 0. I'm just trying to understand the basic operation. I have the greatest part of Classical RPN down. I have used a 35s for the past several years.

I seem to fit in the XYZTL camp if such things have camps to pitch a tent.
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DM42 (2), HP42s, HP35s

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Re: DM42 arrived today! Stack layout?

Post by toml_12953 » Thu May 28, 2020 3:06 am

48GX wrote:
Thu May 28, 2020 1:42 am
Hi toml_12953. Thank you for replying. I had already read through Joe's guide and have read through most of "An Alternative HP-42S/Free42 Manual". I have only skimmed the actual user manual but hope to start on it this weekend.

The Alpha Register seems to be the register that stores the last Alphanumeric entry. Easy enough but it wasn't really spelled out anywhere I could find in "An Alternative HP-42S/Free42 Manual".

I still don't understand the following.

Put a 5 in XYZT and then hit + the stack never changes. Same for filling it with 4 3 2 1 and 4 just falls but T never becomes 0. I'm just trying to understand the basic operation. I have the greatest part of Classical RPN down. I have used a 35s for the past several years.

I seem to fit in the XYZTL camp if such things have camps to pitch a tent.
The T register stays at it's last value and propagates downward when the stack rolls down or drops.

Example:

T 10
Z 4
Y 3
X 2

Press + key. Now the stack shows

T 10
Z 10
Y 4
X 5

2 was added to 3 and the stack dropped down one. Whatever was in the T register was copied downward when the stack dropped.

Now if you press + again:

T 10
Z 10
Y 10
X 9

4 was added to 5 and the stack dropped down again.
Tom L

I bought a moving blanket but it just sits there.

DM10L SN: 059/100
DM41X SN: 00023 (Beta)
DM42 SN: 00025 (Beta)
DM42 SN: 00221 (Shipping)

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48GX
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Re: DM42 arrived today! Stack layout?

Post by 48GX » Thu May 28, 2020 3:10 am

Thank you. I understand the logic behind it now (I believe). Finally makes sense. I just thought it stood for Top.
HP48GX since 1994
DM42 (2), HP42s, HP35s

rprosperi
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Re: DM42 arrived today! Stack layout?

Post by rprosperi » Thu May 28, 2020 3:13 am

48GX wrote:
Thu May 28, 2020 1:42 am
I still don't understand the following.

Put a 5 in XYZT and then hit + the stack never changes. Same for filling it with 4 3 2 1 and 4 just falls but T never becomes 0. I'm just trying to understand the basic operation. I have the greatest part of Classical RPN down. I have used a 35s for the past several years.

I seem to fit in the XYZTL camp if such things have camps to pitch a tent.
While most RPN users find RPL initially disorienting, that's nothing compared to how odd RPN seems, having learned RPL first, so don't feel like you're the first to be confused by some of the initially odd quirks of RPN.

In (nearly all) RPN machines, when the stack drops, the original T register is replicated into the new T, which is useful for a variety reasons, though at first it seems to be an arbitrary action. Fill the stack with different values and play around and you'll better understand what's happening. As you become used to using a fixed-depth stack, you will start to see useful side-effects of T register duplicating, and before long leveraging it as you start to learn more advanced stackrobatics.

I too am in the XYZTL camp. Welcome aboard.

But I agree with TomL, reading the original 42S HP manual is the best way to learn to use it well. The 42S manual is well organized and you should start right from the beginning as it does provide a good overview of the 42's various features and gets to work quickly without much religious "RPN is better..." banter.

Good luck and enjoy your DM42 and 'stepping down' to RPN. Before long, you may find it's also a step up. :)
--bob p

DM42: β00071 & 00282, DM41X: β00071, DM10L: 071/100

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akaTB
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Re: DM42 arrived today! Stack layout?

Post by akaTB » Thu May 28, 2020 6:10 am

It is the law of retaliation for you, RPL addicts, to our discomfort for this:
snapshot.png
snapshot.png (2.12 KiB) Viewed 569 times
:lol: :lol: :lol: :lol:
Greetings,
    Massimo
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Re: DM42 arrived today! Stack layout?

Post by Geoff Quickfall » Thu May 28, 2020 6:21 am

Too funny :!:

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