Hi,

I am trying to reverse engineer a formula from from an HP67 programme. Most of it is pretty clear, however I don't understand what the following program steps from 38 to 45 are doing so can anybody help:

037
038 STO1
039 CHS
040 2
041 ENT
042 Pi
043 x
044 +
045 STO2
046

Thanks,

Bob

It looks like whatever is in X gets stored to register 01 then X is sign-changed, added to 2pi and stored to register 02.

Hi, Bob:

Assuming you've got a value, say N, in the display (X register)
at the beginning, after you execute these steps you'll have:


    In Register 1:      

             N 

    In both Register 2 and the display (X register):

            -N + 2*Pi

but you should delete step 041 ENT, (assuming you mean ENTER),
because ENTER isn't needed to separate the numeric entry "2"
from the constant value "Pi".

Quote:

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but you should delete step 041 ENT, (assuming you mean ENTER),
because ENTER isn't needed to separate the numeric entry "2"
from the constant value "Pi".

---

Doesn't that ENTER mean that you would have

• R1 = N
  
• X = 2Pi+2
  
• Y = -N
  
• R2 = 2Pi +2
  

I'm on the opposite North American coast from my 67, but I have my 41 with me. That distribution is what I get when I run the following program:

• 01 LBL 'TST
  
• 02 STO 01
  
• 03 CHS
  
• 04 2
  
• 05 ENTER^
  
• 06 PI
  
• 07 *
  
• 08 +
  
• 09 STO 02
  

Regards,
Howard

Hi, Howard:

Howard posted:

"Doesn't that ENTER mean that you would have

  R1 = N 

  X = 2Pi+2 

  Y = -N 

  R2 = 2Pi +2 

It depends on whether [ENTER] disables stack lift for the
following numeric entry (so that it overwrites the contents
of the X register) *AND* [PI] is considered a numeric entry
key in the HP-67, which I can't test right now.

I assumed that either that's the case (so that [ENTER], [PI]
does overwrite X) or the original coder wrongly thought it
did, because frankly I find much more plausible that he is trying to compute:


         -N + 2*Pi

which is frequently seen as part of many computations, than:


          2*Pi + 2

which seems pretty useless to me.

Quote:

---

It depends on whether [ENTER] disables stack lift for the following numeric entry (so that it overwrites the contents of the X register) *AND* [PI] is considered a numeric entry key in the HP-67, which I can't test right now.

---

Marcus

Best regards from V.