Comments
Whiskeyjack says: HPR4707 Unix curio - Stack Machines
RE: hpr4707::2026-08-18 UNIX Curio #12 - expr by Vance00:24:27 Listen in ogg, opus, or mp3 format.
I prefer using normal infix notation over RPN, but one of the easiest ways of making an interpreter is to create what is called a "stack machine" which does everything on a stack. Data values get pushed onto a stack, and operators work on the values in the stack. Forth is probably the best known stack oriented programming language.
RPN translates very easily to a stack machine, and dc clearly works with a stack because it gives the error "dc: stack empty" if you make an error such as not providing enough arguments.
I don't know the history of either HP calculators or dc, but I suspect that both may have used RPN more for the reason that it was easiest to implement it that way than because anyone thought it was better from a human perspective.
In episode 4 of my series on industrial controls (HPR4738) I talk about the stack based boolean logic interpreter in the Siemens S5 series PLCs. The concept is fundamental to most industrial controls, although it is often hidden from view.
The Postscript language used in PDF files is also a stack based programming language, so the concept is fairly widely used.
I find the subject of stack based interpreters to be fascinating even though they are not my preferred way of writing programs.
xmanmonk says: Thanks for the episode
RE: hpr4709::2026-08-20 Peertube: my two penneth by Kevie00:18:05 Listen in ogg, opus, or mp3 format.
I'm on sdf (the super dimensional fortress) and have known that they have a toobnix instance running, but never explored that part of the fediverse. I'll check it out now. I've already sent in an email to membership to get a login. Also, I know several of the channels you subscribe to, or at least the people behind them, so I may take a look at those channels/creators as well. Thanks!
Vance says: dc
RE: hpr4707::2026-08-18 UNIX Curio #12 - expr by Vance00:24:27 Listen in ogg, opus, or mp3 format.
Thank you both! Whiskeyjack, you do have a good point. Thirty years ago when I was first learning about UNIX, 'dc' was often included in introductory materials, which is why I said it isn't obscure. However, I probably didn't fully appreciate how the situation has changed since then.
To be blunt, I'm still not a fan of RPN or 'dc' and I don't feel very motivated to dig any deeper into it. But I suppose one never knows; maybe one day it might catch my interest. Actually, regarding the HP calculator I described, its case was as fascinating to me as the device itself - it was the first place I had ever seen Velcro hook-and-loop, which in the 1970s seemed magical!
Whiskeyjack says: Reply to Trey on HPR4708 - PLCs Episode 1
RE: hpr4708::2026-08-19 Programmable Logic Controls - Episode 1 by Whiskeyjack00:19:52 Listen in ogg, opus, or mp3 format.
I am glad that you like the series so far. Episode 1 focuses on the historical relay hardware which preceded PLCs, and from episode 2 and onward I discuss more about the software of PLCs themselves.
You mention cybersecurity. In episode 5, which is HPR4748, I address this issue from the perspective of whether it constitutes a safety issue. You may find that episode interesting.
In episodes 7 and 8, which are not posted yet, I cover more issues relating to PCs in industry.
If you have anything to say about cybersecurity in relation to industrial applications, then I suspect that quite a few listeners would be interested in what you have to say on the subject. You should perhaps think about doing an episode on it. It's not a subject that I think I know enough about from a practical perspective to record an episode about it myself.
Whiskeyjack says: HPR4707 Unix curio - dc
RE: hpr4707::2026-08-18 UNIX Curio #12 - expr by Vance00:24:27 Listen in ogg, opus, or mp3 format.
Having just read some of the background of dc, I would have thought that it would have been worth a "Unix Curio" episode all on its own.
It is obscure in that most people probably didn't know that it exists, it uses RPN notation, which few people use, it didn't become part of the POSIX standard, and it has an interesting relationship to the more commonly used bc.
I might be worth making this a subject of a future Unix Curio.
Trey says: Memories of Ladder Logic
RE: hpr4708::2026-08-19 Programmable Logic Controls - Episode 1 by Whiskeyjack00:19:52 Listen in ogg, opus, or mp3 format.
Hello Whiskeyjack,
Thank you for posting this series. I remember learning about electronics back in the '70s & '80s. I stumbled on some books about ladder logic, and building my first relay based "Holding circuit" blew my mind! What I learned playing with relays and building alarm systems became a foundation on which I have built throughout my career.
For the last few years, I have been researching ICS & OT, primarily from a cybersecurity perspective.
Keep up the fantastic work!
xmanmonk says: Another great show
RE: hpr4707::2026-08-18 UNIX Curio #12 - expr by Vance00:24:27 Listen in ogg, opus, or mp3 format.
I typically use bc or the kde calculator, but there was some stuff here I either forgot or didn't know! Thanks for the info!
Trollercoaster (our of character) says: Woopsie
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
Hey candycanearter07... You sent me a mail, because you were worried you hurt me. That was so nice of you, but I need to apologize: I was too much into my role of grumpy old geek.
So my apologies for worrying you - and thanks a million for reaching out to me. That was so sweet.
Now I'm gonna crouch back into my corner and cry about hurting the world. (don't worry, just slowly sliding back into my role - I'm aye okay, I hope you aretoo)
[note to janitors: I shared this with permission of candycanearter07]
Trollercoaster says: Who's talking about satire?
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
candycanearter07 are you making fun of me?
You're one of those youngsters (definition: under 50), right?
GET OFF MY LAWN!
candycanearter07 says: good satire again
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
i always find your satirical episodes quite enjoyable :)
Trollercoaster says: old guys together
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
Heya old guy,
you weren't supposed to hear this. Ken asked it for those youngsters out there. You can just continue your bug fix for xrandr in Cobol.
old guy says: :-)
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
nice listening, nice rant ... enjoyed it! thx
Trollercoaster says: One left in my six pack
RE: hpr4705::2026-08-14 Free Software Is Wasted On You Teens by Trollercoasterfrom the series Freedom is not Free .00:24:14 Listen in ogg, opus, or mp3 format.
Since Ken didn't come over to pick up that last beer from my six pack... (Delirium Tremens, an old time favorite of mine), I sugeest you look me up when you're coming over for FOSDEM in February. We'll have one together.
Glad you enjoyed the show.
candycanearter07 says: re: Audacity for noise music
RE: hpr4692::2026-07-28 Noise Music Tutorial 2: Using Audacity to Make Noise by TheDUDE00:08:48 Listen in ogg, opus, or mp3 format.
I don't know why it wouldnt be? You could just use localstorage to save the image as a .wav file and use a player to play it, likely.
Jack says: Misleading
RE: hpr4703::2026-08-12 Ebooks and Audiobooks by Ahuka00:07:59 Listen in ogg, opus, or mp3 format.
Slick way of getting an unwarranted dig against the President. Maybe check your facts first.
Kobo raised e-reader prices in the US and Canada by $20 to $30 per device, affecting popular models like the Kobo Clara BW ($159.99), Kobo Clara Colour ($179.99), and Kobo Libra Colour ($259.99). While industry analysts point to broader component and manufacturing cost pressures, Kobo implemented these mid-cycle adjustments directly across retail channels without citing specific tariff policy triggers.
Updated US Pricing Breakdown
Kobo Clara BW: $159.99 (previously $139.99)
Kobo Clara Colour: $179.99 (previously $159.99)
Kobo Libra Colour: $259.99 (previously $229.99)
Archer72 says: Audiobooks and Audible
RE: hpr4703::2026-08-12 Ebooks and Audiobooks by Ahuka00:07:59 Listen in ogg, opus, or mp3 format.
Hi Ahuka,
Thank you for this show. I am going down an Audible rabbit hole that I should have avoided. Thankfully there is Libation set up on my server to Liberate those book in original m4b format and an option for mp3 in long format. I'm sure there is FLOSS tool for making chapters (other than Audacity).
https://getlibation.com
candycanearter07 says: re: a refreshing contrast...
RE: hpr3766::2023-01-09 ACER Nitro 5 laptop review by Bookewyrmm00:09:48 Listen in ogg, opus, or mp3 format.
and now its been 3 years since it was recorded :D i wonder if booke is still around to make a followup on this if theyre still using it...
candycanearter07 says: useful!!
RE: hpr4703::2026-08-12 Ebooks and Audiobooks by Ahuka00:07:59 Listen in ogg, opus, or mp3 format.
i used to love using the little rentable mp3 players from the library, this is totally up my alley :D
candycanearter07 says: useful!
RE: hpr4697::2026-08-04 Correcting the Dates of Files by Vance00:11:57 Listen in ogg, opus, or mp3 format.
since different filesystems have different ways to store dates, this kinda thing is useful in a ton of senarios! thanks
wevaba6950 says: A refreshing contrast between enterprise gear and low-power hardware
RE: hpr3766::2023-01-09 ACER Nitro 5 laptop review by Bookewyrmm00:09:48 Listen in ogg, opus, or mp3 format.
It’s rare to find a long-term review that actually covers two full years of daily use, especially for something as niche as the Pinebook Pro. I was particularly struck by the point about how the ARM architecture forces you to be more intentional with your workflow—knowing exactly what the hardware can and cannot handle before you even open a browser tab.
I spend most of my time working on the opposite end of the performance spectrum, usually configuring enterprise storage arrays with high-end Fibre Channel HBAs and dedicated RAID controllers https://serverorbit.com/hba-and-controllers/fiber-channel/raid-controller-en. In that world, everything is about maximum throughput and zero latency, so the idea of a $200 "daily driver" feels like a real shift in perspective. However, I’ve found that for simple tasks like monitoring a RAID rebuild or checking controller logs via SSH, you really don't need a massive workstation. There’s something very satisfying about using a low-power, fanless machine to manage a high-power server rack. It really makes you appreciate efficiency over raw horsepower.
After two years, do you think the battery degradation on the Pinebook has stayed manageable, or is it starting to feel more like a "desk-bound" laptop now?
Henrik Hemrin says: Exif in digiKam
RE: hpr4697::2026-08-04 Correcting the Dates of Files by Vance00:11:57 Listen in ogg, opus, or mp3 format.
DigiKam, an open source Photo management tool (which I happen to have talked shortly about here at HPR) make use of ExifTool and Exiv2.
I am not the person to explain any of them in more detail. For reference one passage in the digiKam documentation regarding them: https://docs.digikam.org/en/setup_application/metadata_settings.html
Whiskeyjack says: Reply to Archer72 on HPR4708 - PLCs Episode 1
RE: hpr4708::2026-08-19 Programmable Logic Controls - Episode 1 by Whiskeyjack00:19:52 Listen in ogg, opus, or mp3 format.
I am glad you are finding this interesting. Episode 1 focuses on relay technology, as this is important background for understanding what replaced them when hard wired relay based logic was replaced by software in industrial control systems since the latter evolved directly from the former. Industrial control systems largely took a very different evolutionary path from conventional computers in terms of software concepts and programming languages and so it takes some basic grounding in programming with relays to understand what came next.
From episode 2 onward I start dealing with actual PLCs and related systems. If you have previous experience with PLCs, you may still find the historical background interesting as I cover some of the older systems in some detail as their simplicity makes the explanations easier.
The series has a total of 8 episodes recorded and 6 posted so far. I will post the remaining 2 as slots open up in the calendar.
If anyone has any questions about what I cover in this series I will be happy to answer them in a follow up episode if I can. I have skimmed over this topic very lightly and in very simple terms in order to make it more interesting to people who are not familiar with the field. I would be happy to go into more depth on any of these topics.
I am also working on a follow up episode on a closely related topic which will get posted after the series winds up near the end of the year.
Windigo says: Fantastic episode
RE: hpr4581::2026-02-23 Sharp Intake of Breath City (A.K.A.) How I learnt to stop worrying about the fork bomb by not_toby00:36:31 Listen in ogg, opus, or mp3 format.
I deeply enjoyed your introductory episode. I find it fascinating to hear about everyone's different backgrounds and experiences!
A note on "Meanwhile, back at the point": I believe the Linux Outlaws adopted it from the LugRadio podcast (https://lugradio.org/), which is another fantastic (although long-defunct) podcast worth listening to.
I don't know if it goes further back than that. :)
Archer72 says: Thanks you
RE: hpr4708::2026-08-19 Programmable Logic Controls - Episode 1 by Whiskeyjack00:19:52 Listen in ogg, opus, or mp3 format.
Hi,
Thank you for this series. I am just a little ways into the first in the series. With living in 'Toyota country' (Kentucky), this is quite interesting though I am not in the industry anymore.
Being in the electrical/electronic industry by trade in the past makes for good listening.
I may very well get back into this in time.
Cheers,
Archer72
Vance says: Modifying metadata
RE: hpr4697::2026-08-04 Correcting the Dates of Files by Vance00:11:57 Listen in ogg, opus, or mp3 format.
Thanks very much, Jim, glad you found it to be helpful! It appears that "exiftags" does not have the ability to modify EXIF tags, just read them. A quick search turned up "exiftool", "jhead", and "exiv2" as potential utilities to make modifications, but I have no experience with any of them.
I'm not sure I can blame Android for not being able to use an SD card. As mentioned, the old phone seemed to have some hardware problems, so that could be the cause. I would agree that the software environment definitely steers users toward Google's interests and would be interested in an episode about reclaiming some freedom.
Windigo says: Audacity for noise music
RE: hpr4692::2026-07-28 Noise Music Tutorial 2: Using Audacity to Make Noise by TheDUDE00:08:48 Listen in ogg, opus, or mp3 format.
I watched a high school student's presentation on his technique for making noise with audacity.
He used MS paint to create scribbles and drawings, saved them as bitmap images, and imported them as raw audio. He changed the composition of the noise and length of the audio by choosing different colors, making different impressions, and changing the image size. It was pretty wild, although a very manual process!
I wonder if the same kind of technique would be possible with Javascript/HTML canvas?
Archer72 says: Glasses and age
RE: hpr4655::2026-06-05 Tips for Glasses by norrist00:09:50 Listen in ogg, opus, or mp3 format.
Thanks for this too.
Operat0r, a lot of us geeks are over 50 I would guess.
I also keep the font size at 150% and immediately look for the scale setting on a new application. If the application is coded correctly, it is just ++<+>
This scale may increase to 175% depending on the time of day, mostly early in the morning.
Whiskeyjack says: Reply to candycanearter07 in HPR4698 ID3 tags
RE: hpr4698::2026-08-05 ID3 Tags and Vorbis Comments by Whiskeyjack00:32:55 Listen in ogg, opus, or mp3 format.
I only accidentally discovered that HPR MP3 files had both v1 and v2 tags while preparing this episode. I noticed that the tags shown by the ID3 program did not match exactly what was appearing in the Totem music player software. A bit of experimenting showed that both V1 and V2 were indeed there. ID3v2 are at the start of the file (you can use "head" to view them), and ID3v1 tags are at the end (you can use "tail" to see them there). That made for a more interesting podcast than I had planned on.
I have to wonder how common this practice is.
Th3Dud3 says: response to Kevin not being able to get cream ale
RE: hpr4696::2026-08-03 HPR Community News for July 2026 by HPR Volunteersfrom the series HPR Community News.00:50:52 Listen in ogg, opus, or mp3 format.
Now I see why we dumped all your tea.in the harbor since you don't have our watery beer lmao. No in all seriousness it's probably due to the tariffs. They really screwed up a lot of things trade wise. Like I was going to buy a cheap used yamaha keytar, but since due to tariffs and import fees, it cost as much as a new alesis vortex, so I bought that instead. Hopefully within the decade the tariffs will be gone and American hill billy adjunct lager styles can be readily available.
Whiskeyjack says: Reply to xmanmonk in HPR4698 - ID3 Tags
RE: hpr4698::2026-08-05 ID3 Tags and Vorbis Comments by Whiskeyjack00:32:55 Listen in ogg, opus, or mp3 format.
I am glad you liked the episode.
I covered the "tail" method for reading ID3v1 tags including how to get just the ID3 tags at the end without any of the music which comes before it, plus handling non-printable characters.
Since the tags are fixed length strings of known length, you should be able to use "cut" to extract individual fields after using "tail" to get the entire block of data, although I have not tried this particular refinement.
More Information...
Copyright Information
Unless otherwise stated, our shows are released under a Creative Commons Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0) license.
The HPR Website Design is released to the Public Domain.