7 ms·

The Computer at the Bottom of a Canal

183 points by Kudos 2mo ago

throw83939r0r 2mo ago
Too bad british goverments had to kill companies like that. But the new business plan is going much better!
- psd1 2mo ago
  Your embarrassment could have been avoided by reading TFA.
inigyou 2mo ago
I wonder if you could throw a small microcontroller at the bottom of a canal, powered by water passing through a fan, to hide it. And why you would want to do that.
- ErroneousBosh 2mo ago
  Water quality monitoring. Communicate back to the surface with ultrasonic pulses.
  - arnsholt 2mo ago
    And in case people think ultrasonic signaling isn’t a real thing, it very much is. In the oil and gas industry, it’s how measurements taken while drilling a hole are sent back to the surface through the drilling mud.
    - doodlebugging 2mo ago
      Downhole tools used in MWD/LWD do not use ultrasonic frequencies. Drilling is a very noisy environment. The first tool that I used employed a downhole pulser with a surface transducer and operated at about 0.5-1 Hz. That's not ultrasonic. It was a pretty low frequency signal. Data transmission rates limit the volume of information that can be transmitted from the downhole tool to the surface where they are decoded. Your tool has to set up a pressure wave in the mud column that is detectable miles away from the tool while the well is being drilled. This is a good recent paper authored by an experienced drilling engineer about MWD/LWD drilling history and pulser designs and data rates that can be expected. https://www.aade.org/application/files/1917/4604/2319/AADE-25-NTCE-005_-_Chin.pdf https://www.aade.org/application/files/1917/4604/2319/AADE-2...
      - arnsholt 2mo ago
        Oh derp. It’s been a while since I worked adjacent to this, so I clearly misremembered some important bits. Thanks for the correction!
        doodlebugging 2mo ago
        Boy how I wish it had used ultrasonic frequencies. Sadly enough though, I spent large parts of every day in front of a laptop connected to a transducer waiting for signals to appear in the noisy stream of data coming from the standpipe transducer. Every few seconds if your tool still functioned you would get the first bit of a signal that contained toolface orientation information and gamma ray data if you had a gamma ray sub. It was a binary stream of ones and zeroes where a 1 was a pressure increase and a zero was a decrease to background. You needed to be quick on the decode because the directional driller on the rig floor was using the real-time toolface orientation to help steer the drill bit to the target formation and on to TD (total depth). As the days went by and the hole was progessively deeper it was inevitable that some part of the downhole BHA (bottom-hole assembly) would fail due to erosion from the drilling mud, erosion at the bit/formation interface, friction along the borehole wall, etc. The hope was always that your tool would function well enough until something else failed and necessitated a round trip to replace a critical component. The costs of the round trip were placed on the service company that had the failed equipment so even if your company supplied the MWD/LWD services and the directional drilling services (DD), if your tool failed the cost of the trip fell on your service and impacted your service quality assessment which affected your rig bonus calculation. It was common for a DD with a failing mud motor to hang around the MWD shack or keep the MWD engineers on the phone, harassing the engineers to get them to admit that their tool is nearing the point where the toolface data was so low level that it was undecodable. If he could hang the trip on the MWD he would every time so the MWD engineers were incentivized to struggle through poor signal for as long as possible when they knew from the pressure data that the mud motor was about to crater or that the drill bit needed to be replaced. Battery failures and erosion of the pulser valve components that resulted in signal amplitudes diminishing to the point where they were undetectable were the things you knew would happen and you just hoped that downhole conditions killed someone else's tool before yours inevitably failed.
- lexicality 2mo ago
  canals have negligible water flow (except during disasters!) so I don't think that'd work very well. They also get dredged occasionally so there's a decent chance anything you leave down there won't last more than a couple of years
  - fragmede 2mo ago
    They do have tides though, so make it a big fan that points up.
    - wbl 2mo ago
      Depends on the canal. The UK narrow boat network has locked everywhere so minimal current in most sections similarly the Netherlands. In fact most canals. But then you have something like Suez which is just open to the ocean.
      - fragmede 2mo ago
        The UK locks themselves are water movement though, so if you wanted to power something for "free" on those, you'd attach it to there. Oh man did I love watching those as a kid. You wouldn't do a fan though, you'd have a line and a buoy and use the up and down motion to drive a linear electromagnetic generator to harvest energy.
        fennecbutt 2mo ago
        Yeah but it's not really a lateral flow of water when the locks fill up and empty.
        lexicality 2mo ago
        you do get lateral flow up/downstream during filling and emptying, but it's generally considered rude to do it fast enough to cause turbulence
  - DonHopkins 2mo ago
scottconover 2mo ago
Website design comment: I love the orange/teal theme! Really drawn to the details such as illustrations carrying the orange/teal theme. Inspired me to re-color a project with this split complimentary color.
- g-b-r 2mo ago
  I personally hate the colors; I don't know if it was vibe coded, but it resembles the browns that GPT loves a lot. I'm looking at it from a crappy screen, though.
  - g-b-r 2mo ago
    Ok, I forgot about it, that was with dark mode enabled. Without it it's much better.
Hnrobert42 2mo ago
I console myself that this is why I never got fabulously wealthy. That brilliance is no guarantee of wealth. You need luck, too. But the truth is, you also need to do the work. I used my conclusion about luck as an excuse to not even try. Not even in some grand way. Just in the grinding everyday way. In the way of, "You know what I should do?! I should ... meh. That'll never work." Take it from me, kids. If you want to do something great, do it while you are still young enough to believe it's possible.
Taniwha 2mo ago
Thing is capability machines (like this and the 432 and lots of research machines) were very much the thing at the time - cutting edge even. The research literature was full of them. I did a paper design at the time. What ate them up was "what can you fit all on a chip with not many pins", followed by "what can you fit along with a cache on a chip with more pins", things move so much faster if everything's on the same die. Tagged architectures are old, Burroughs mainframes had them back in the 70s along with rudimentary hardware objects (pageable even)
- ishanmahapatra 2mo ago
  Can you expand on your paper computer? It sounds fascinating.
  - Taniwha 2mo ago
    It was more than 40 years ago, before I had the skills to build chips, I'm afraid I've kept nothing of that design
    - ishanmahapatra 2mo ago
      No worries. Before your comment, I didn’t even know about this type of computer. This is my new rabbit hole. Thank you for that.
- tclancy 2mo ago
  The end of the article seems to admit all of what you say but then suggest it is time to revisit; do you think that’s valid or no?
  - Taniwha 2mo ago
    I'm in 2 minds, I'm strongly in the RISC camp these days, I know how hard it is to build a truly performant CPU and think that simpler is better as far as ISAs go. Adding segmentation hardware into the addressing path means more clocks and makes it's harder to detect loads/stores that interfere with each other (all load/stores have to block each other until the addressing/tlb lookup has been done ie detecting aliasing ). A true capability architecture needs separate register files for pointers and data with protections enforced when the address registers are loaded/stored, it's a step away from our models of linear address spaces that many of the languages we use today are based on. And any new CPU that requires everyone to learn a new language is probably a non-starter as a mainstream CPU
tibbydudeza 2mo ago
I read about them in Byte Magazine - the names were memorable - Objek - Numerik and a third chip - there were no silicon afaik but jsut emulator circuit boards run by a Sun workstation.
- EdwardCoffin 2mo ago
  Objekt, Numerik, Logik, Klock, according to Wikipedia [1] [1] https://en.wikipedia.org/wiki/Rekursiv#Physical_packaging https://en.wikipedia.org/wiki/Rekursiv#Physical_packaging
fuzzfactor 2mo ago
>In my essay a distribution of one I argued that bespoke software was the original, correct arrangement, that fifty years of productised general-purpose software were a compromise forced by the economics of scarce programmers, and that AI has ended the compromise. I would also say that productised general-purpose software was an undue bonanza taking unfair advantage of copyright, which shouldn't have allowed so many restrictions on code which is necessary to make devices perform their intended tasks. Fortunately AI has been able to get started accomplishing some of the much-needed workarounds to these annoying copyright issues, like few humans have been able to do. Regardless of whether programmers are scarce or abundant. On a tangent, it sounds like a famous canal, but I would figure there are a number of little-known waterways where there might be a high-performance 21st century PC resting underwater along with some poor soul's bitcoin wallet :(
- leoc 2mo ago
  The "A Distribution of One" argument seems less convincing than the "The Computer at the Bottom of a Canal" one. I'm no expert, but if you've ever read some of the computing press from the time you'll know that custom software was still rather popular well into the '80s: and unfortunately custom software written for in-house use by a non-software company was the classic venue for all the Software Crisis war stories, which probably has a lot more to do with why it went out of fashion than progammer wages on their own. Whether the main problem was the difficulty of extracting requirements from users and management or the lack of sufficiently good software developers, maybe the arrival of LLM software cannons will be what it takes to fix it, but a hae ma doots.
dpedu 2mo ago
What remains of this computer? Diagrams? Code? Anything that would let us take a closer look at how it works?
JSR_FDED 2mo ago
It’s crazy what a small group of smart people can achieve if they’re not captive to conventional wisdom. They got crushed by the commodity curve and Moore’s Law. But still a great story - and thankfully written by a real person. The author’s idea that the commodity curve is over and that hardware is now cheap enough to make special purpose hardware viable is intriguing. Standardization used to be important because you needed to convince scarce programmers to invest in the platform, but AI has ended the scarcity of programmers so dedicated purpose hardware is more viable than ever.
- imglorp 2mo ago
  There are several cycles that bring tech ideas in and out of fashion because of market conditions, intersecting tech cycles, other implications of Moore's Law, or whatever. Another trend, for example, might be centralized vs distributed: terminals (thin clients) and mainframes gave way to fat client PCs on prem, and then back to thin clients with cloud stuff.
ozhero 2mo ago
A fascinating story. I owned a Linn Sondek turntabe in the 70's with a Denon cartridge. Spent a crazy amount on Hi-Fi chasing the audiophile dream :-)
needSomeCoffee 2mo ago
Very interesting and well written article. This sentence in particular: "Linn Products is the Glasgow company Ivor Tiefenbrun founded in 1972, and if you know it at all you know it for the Sondek LP12, still widely regarded by its partisans as the finest record deck ever made." I was a big audiophile right at that time. Auditioned both Sondek and Sota Star Saphire. Went with the latter which I still proudly own (Alphason Tonearm). Note how carefully the author phrased "...by its partisans..." when describing the Sondek as the best. Nothing, not even programing code style zealots today can compare to audiophiles and their "take" on what made for the best playback. Pretty sure the author did not want to open that can of worms by simply declaring the Sondek the best. Turntables back then were pretty damn detailed re: technology. Not surprised Linn could make a great computer (in the day). HTH, NSC
- stavros 2mo ago
  Yeah but also saying "it's considered the best by the people who love it" is a tautology.
  - n49o7 2mo ago
    Therein lies the humor, imo.
fwipsy 2mo ago
I don't think this is AI, but the writing style keeps reminding me of AI. I'm trying to isolate why. I think it's something to do with the information density. The sentences twist and turn, have lots of related ideas, digressions, and little details without much lead-in. The wording is also very precise, which is another characteristic of AI writing. This sounds like a critique, but I actually find it charming. This sentence is a strong illustration of what I'm talking about: > Since only OBJEKT ever knew where anything physically lived, objects could be relocated freely without touching a reference, so garbage collection went into the silicon too: a two-space compacting collector that walked the live objects and slid them into the other half of DRAM while execution carried on above, oblivious. I mean, come on. Run-ons are one thing, but this is practically a lecture in a single sentence. :P
- Luc 2mo ago
  Very well-written text, not a whiff of AI generation to it. Your example is not even a run-on sentence! I enjoyed reading it, many thanks to the author.
  - fwipsy 2mo ago
    Yeah I'm not sure, just identifying that subjectively, this is the impression I get. Maybe I just associate any style which is especially fluent and avoids vernacular with AI at this point.
  - tclancy 2mo ago
    I really enjoyed it, but I think there’s more than a whiff. > That curve is gone. The compromise is going with it; and the workload-shaped machine, the thing Harland was building in 1984, is what comes back.
    - deleted 2mo ago
      [deleted]
    - Luc 2mo ago
      Nope, and Pangram agrees with me, 100% human written with high confidence. I really enjoy this style and I think it's not _that_ close to AI output (it's much better in fact).
tmzt 2mo ago
The 40-bit hashed address seemed familiar, then I realized that I (and Claude) had used a similar concept in a VM we built for the OS I've been building. It's a capability and typing system that enables import boundaries to be enforced and third-party packages are unable to perform security sensative operations without being specially signed. It's also a "distribution of one" concept as the user builds their own UI to their specification personalising the OS.

183 points by Kudos 2mo ago

throw83939r0r 2mo ago

Too bad british goverments had to kill companies like that. But the new business plan is going much better!

psd1 2mo ago
Your embarrassment could have been avoided by reading TFA.

inigyou 2mo ago

I wonder if you could throw a small microcontroller at the bottom of a canal, powered by water passing through a fan, to hide it. And why you would want to do that.

ErroneousBosh 2mo ago
Water quality monitoring. Communicate back to the surface with ultrasonic pulses.
- arnsholt 2mo ago
  And in case people think ultrasonic signaling isn’t a real thing, it very much is. In the oil and gas industry, it’s how measurements taken while drilling a hole are sent back to the surface through the drilling mud.
  - doodlebugging 2mo ago
    Downhole tools used in MWD/LWD do not use ultrasonic frequencies. Drilling is a very noisy environment. The first tool that I used employed a downhole pulser with a surface transducer and operated at about 0.5-1 Hz. That's not ultrasonic. It was a pretty low frequency signal. Data transmission rates limit the volume of information that can be transmitted from the downhole tool to the surface where they are decoded. Your tool has to set up a pressure wave in the mud column that is detectable miles away from the tool while the well is being drilled. This is a good recent paper authored by an experienced drilling engineer about MWD/LWD drilling history and pulser designs and data rates that can be expected. https://www.aade.org/application/files/1917/4604/2319/AADE-25-NTCE-005_-_Chin.pdf https://www.aade.org/application/files/1917/4604/2319/AADE-2...
    - arnsholt 2mo ago
      Oh derp. It’s been a while since I worked adjacent to this, so I clearly misremembered some important bits. Thanks for the correction!
      - doodlebugging 2mo ago
        Boy how I wish it had used ultrasonic frequencies. Sadly enough though, I spent large parts of every day in front of a laptop connected to a transducer waiting for signals to appear in the noisy stream of data coming from the standpipe transducer. Every few seconds if your tool still functioned you would get the first bit of a signal that contained toolface orientation information and gamma ray data if you had a gamma ray sub. It was a binary stream of ones and zeroes where a 1 was a pressure increase and a zero was a decrease to background. You needed to be quick on the decode because the directional driller on the rig floor was using the real-time toolface orientation to help steer the drill bit to the target formation and on to TD (total depth). As the days went by and the hole was progessively deeper it was inevitable that some part of the downhole BHA (bottom-hole assembly) would fail due to erosion from the drilling mud, erosion at the bit/formation interface, friction along the borehole wall, etc. The hope was always that your tool would function well enough until something else failed and necessitated a round trip to replace a critical component. The costs of the round trip were placed on the service company that had the failed equipment so even if your company supplied the MWD/LWD services and the directional drilling services (DD), if your tool failed the cost of the trip fell on your service and impacted your service quality assessment which affected your rig bonus calculation. It was common for a DD with a failing mud motor to hang around the MWD shack or keep the MWD engineers on the phone, harassing the engineers to get them to admit that their tool is nearing the point where the toolface data was so low level that it was undecodable. If he could hang the trip on the MWD he would every time so the MWD engineers were incentivized to struggle through poor signal for as long as possible when they knew from the pressure data that the mud motor was about to crater or that the drill bit needed to be replaced. Battery failures and erosion of the pulser valve components that resulted in signal amplitudes diminishing to the point where they were undetectable were the things you knew would happen and you just hoped that downhole conditions killed someone else's tool before yours inevitably failed.
lexicality 2mo ago
canals have negligible water flow (except during disasters!) so I don't think that'd work very well. They also get dredged occasionally so there's a decent chance anything you leave down there won't last more than a couple of years
- fragmede 2mo ago
  They do have tides though, so make it a big fan that points up.
  - wbl 2mo ago
    Depends on the canal. The UK narrow boat network has locked everywhere so minimal current in most sections similarly the Netherlands. In fact most canals. But then you have something like Suez which is just open to the ocean.
    - fragmede 2mo ago
      The UK locks themselves are water movement though, so if you wanted to power something for "free" on those, you'd attach it to there. Oh man did I love watching those as a kid. You wouldn't do a fan though, you'd have a line and a buoy and use the up and down motion to drive a linear electromagnetic generator to harvest energy.
      - fennecbutt 2mo ago
        Yeah but it's not really a lateral flow of water when the locks fill up and empty.
        lexicality 2mo ago
        you do get lateral flow up/downstream during filling and emptying, but it's generally considered rude to do it fast enough to cause turbulence
- DonHopkins 2mo ago

scottconover 2mo ago

Website design comment: I love the orange/teal theme! Really drawn to the details such as illustrations carrying the orange/teal theme. Inspired me to re-color a project with this split complimentary color.

g-b-r 2mo ago
I personally hate the colors; I don't know if it was vibe coded, but it resembles the browns that GPT loves a lot. I'm looking at it from a crappy screen, though.
- g-b-r 2mo ago
  Ok, I forgot about it, that was with dark mode enabled. Without it it's much better.

Hnrobert42 2mo ago

I console myself that this is why I never got fabulously wealthy. That brilliance is no guarantee of wealth. You need luck, too. But the truth is, you also need to do the work. I used my conclusion about luck as an excuse to not even try. Not even in some grand way. Just in the grinding everyday way. In the way of, "You know what I should do?! I should ... meh. That'll never work." Take it from me, kids. If you want to do something great, do it while you are still young enough to believe it's possible.

Taniwha 2mo ago

Thing is capability machines (like this and the 432 and lots of research machines) were very much the thing at the time - cutting edge even. The research literature was full of them. I did a paper design at the time. What ate them up was "what can you fit all on a chip with not many pins", followed by "what can you fit along with a cache on a chip with more pins", things move so much faster if everything's on the same die. Tagged architectures are old, Burroughs mainframes had them back in the 70s along with rudimentary hardware objects (pageable even)

ishanmahapatra 2mo ago
Can you expand on your paper computer? It sounds fascinating.
- Taniwha 2mo ago
  It was more than 40 years ago, before I had the skills to build chips, I'm afraid I've kept nothing of that design
  - ishanmahapatra 2mo ago
    No worries. Before your comment, I didn’t even know about this type of computer. This is my new rabbit hole. Thank you for that.
tclancy 2mo ago
The end of the article seems to admit all of what you say but then suggest it is time to revisit; do you think that’s valid or no?
- Taniwha 2mo ago
  I'm in 2 minds, I'm strongly in the RISC camp these days, I know how hard it is to build a truly performant CPU and think that simpler is better as far as ISAs go. Adding segmentation hardware into the addressing path means more clocks and makes it's harder to detect loads/stores that interfere with each other (all load/stores have to block each other until the addressing/tlb lookup has been done ie detecting aliasing ). A true capability architecture needs separate register files for pointers and data with protections enforced when the address registers are loaded/stored, it's a step away from our models of linear address spaces that many of the languages we use today are based on. And any new CPU that requires everyone to learn a new language is probably a non-starter as a mainstream CPU

tibbydudeza 2mo ago

I read about them in Byte Magazine - the names were memorable - Objek - Numerik and a third chip - there were no silicon afaik but jsut emulator circuit boards run by a Sun workstation.

EdwardCoffin 2mo ago
Objekt, Numerik, Logik, Klock, according to Wikipedia [1] [1] https://en.wikipedia.org/wiki/Rekursiv#Physical_packaging https://en.wikipedia.org/wiki/Rekursiv#Physical_packaging

fuzzfactor 2mo ago

>In my essay a distribution of one I argued that bespoke software was the original, correct arrangement, that fifty years of productised general-purpose software were a compromise forced by the economics of scarce programmers, and that AI has ended the compromise. I would also say that productised general-purpose software was an undue bonanza taking unfair advantage of copyright, which shouldn't have allowed so many restrictions on code which is necessary to make devices perform their intended tasks. Fortunately AI has been able to get started accomplishing some of the much-needed workarounds to these annoying copyright issues, like few humans have been able to do. Regardless of whether programmers are scarce or abundant. On a tangent, it sounds like a famous canal, but I would figure there are a number of little-known waterways where there might be a high-performance 21st century PC resting underwater along with some poor soul's bitcoin wallet :(

leoc 2mo ago
The "A Distribution of One" argument seems less convincing than the "The Computer at the Bottom of a Canal" one. I'm no expert, but if you've ever read some of the computing press from the time you'll know that custom software was still rather popular well into the '80s: and unfortunately custom software written for in-house use by a non-software company was the classic venue for all the Software Crisis war stories, which probably has a lot more to do with why it went out of fashion than progammer wages on their own. Whether the main problem was the difficulty of extracting requirements from users and management or the lack of sufficiently good software developers, maybe the arrival of LLM software cannons will be what it takes to fix it, but a hae ma doots.

dpedu 2mo ago

What remains of this computer? Diagrams? Code? Anything that would let us take a closer look at how it works?

JSR_FDED 2mo ago

It’s crazy what a small group of smart people can achieve if they’re not captive to conventional wisdom. They got crushed by the commodity curve and Moore’s Law. But still a great story - and thankfully written by a real person. The author’s idea that the commodity curve is over and that hardware is now cheap enough to make special purpose hardware viable is intriguing. Standardization used to be important because you needed to convince scarce programmers to invest in the platform, but AI has ended the scarcity of programmers so dedicated purpose hardware is more viable than ever.

imglorp 2mo ago
There are several cycles that bring tech ideas in and out of fashion because of market conditions, intersecting tech cycles, other implications of Moore's Law, or whatever. Another trend, for example, might be centralized vs distributed: terminals (thin clients) and mainframes gave way to fat client PCs on prem, and then back to thin clients with cloud stuff.

ozhero 2mo ago

A fascinating story. I owned a Linn Sondek turntabe in the 70's with a Denon cartridge. Spent a crazy amount on Hi-Fi chasing the audiophile dream :-)

needSomeCoffee 2mo ago

Very interesting and well written article. This sentence in particular: "Linn Products is the Glasgow company Ivor Tiefenbrun founded in 1972, and if you know it at all you know it for the Sondek LP12, still widely regarded by its partisans as the finest record deck ever made." I was a big audiophile right at that time. Auditioned both Sondek and Sota Star Saphire. Went with the latter which I still proudly own (Alphason Tonearm). Note how carefully the author phrased "...by its partisans..." when describing the Sondek as the best. Nothing, not even programing code style zealots today can compare to audiophiles and their "take" on what made for the best playback. Pretty sure the author did not want to open that can of worms by simply declaring the Sondek the best. Turntables back then were pretty damn detailed re: technology. Not surprised Linn could make a great computer (in the day). HTH, NSC

stavros 2mo ago
Yeah but also saying "it's considered the best by the people who love it" is a tautology.
- n49o7 2mo ago
  Therein lies the humor, imo.

fwipsy 2mo ago

I don't think this is AI, but the writing style keeps reminding me of AI. I'm trying to isolate why. I think it's something to do with the information density. The sentences twist and turn, have lots of related ideas, digressions, and little details without much lead-in. The wording is also very precise, which is another characteristic of AI writing. This sounds like a critique, but I actually find it charming. This sentence is a strong illustration of what I'm talking about: > Since only OBJEKT ever knew where anything physically lived, objects could be relocated freely without touching a reference, so garbage collection went into the silicon too: a two-space compacting collector that walked the live objects and slid them into the other half of DRAM while execution carried on above, oblivious. I mean, come on. Run-ons are one thing, but this is practically a lecture in a single sentence. :P

Luc 2mo ago
Very well-written text, not a whiff of AI generation to it. Your example is not even a run-on sentence! I enjoyed reading it, many thanks to the author.
- fwipsy 2mo ago
  Yeah I'm not sure, just identifying that subjectively, this is the impression I get. Maybe I just associate any style which is especially fluent and avoids vernacular with AI at this point.
- tclancy 2mo ago
  I really enjoyed it, but I think there’s more than a whiff. > That curve is gone. The compromise is going with it; and the workload-shaped machine, the thing Harland was building in 1984, is what comes back.
  - deleted 2mo ago
    [deleted]
  - Luc 2mo ago
    Nope, and Pangram agrees with me, 100% human written with high confidence. I really enjoy this style and I think it's not _that_ close to AI output (it's much better in fact).

tmzt 2mo ago

The 40-bit hashed address seemed familiar, then I realized that I (and Claude) had used a similar concept in a VM we built for the OS I've been building. It's a capability and typing system that enables import boundaries to be enforced and third-party packages are unable to perform security sensative operations without being specially signed. It's also a "distribution of one" concept as the user builds their own UI to their specification personalising the OS.