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41: What's the significance of the alpha mark (ᵀ) prefix on catalog 2 entries?
01-24-2020, 01:28 AM
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RE: 41: What's the significance of the alpha mark (ᵀ) prefix on catalog 2 entries?
(01-23-2020 11:03 PM)Dave Britten Wrote:  
(01-23-2020 11:00 PM)Thomas Okken Wrote:  Supporting ALPHA arguments for arbitrary programmable functions was a bit difficult on the 41 because the opcode space was pretty much used up, and XROM functions don't support arguments at all. Squeezing that in would have required some rather drastic measures in the command interpreter.

They did eventually make those changes, on a machine that had more RAM and especially ROM so that functionality could be put to good use. I'm referring, of course, to the 42S.

That would certainly explain it, then (emphasis mine). It's just a shame the 42S didn't have any ROM expansion capabilities to take advantage of it!

XROMs do support arguments on the HP-41. This was used by the PRP function in the printer to select a program to print. In fact, the command interpreter on the HP-41 is quite capable of handling arguments for XROMs, but it saw limited use. Probably due to this, the command interpreter also had a couple of bugs related to XROMs that I have fixed in the IFG ROM variant for the 41CL.

The main problem with supporting arguments with XROMs on the HP-41 is that they cannot be stored into programs. This is because the user can unplug a module and then there is no way to know whether it would use any argument, making it impossible to properly display a program. There are a couple of ways around this to make this somewhat possible. One is the semi-merged feature I use in the Ladybug module, being generalized in a coming OS extension module that I am currently working on.
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RE: 41: What's the significance of the alpha mark (ᵀ) prefix on catalog 2 entries? - hth - 01-24-2020 01:28 AM



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