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I am experimenting with a graphics pen and tablet and it got me thinking about the difference between it and my mouse. One huge difference is that the tablet's working area covers the whole screen, so that you can tap on an absolute position. My mouse always outputs relative x/y from its last position. This is obviously a huge benefit because it does not restrict the mouse to one part of your desk. I am wondering if this was how the original mice/trackballs/whatevers did, or were they absolute position?

Michael Stachowsky
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    A useful test case for this: Move your mouse towards the top of the mouse pad, then turn it 90 degrees and move it down to the bottom. How would one capture that absolute path? At a bare minimum it either needs to encode the information on the mat or have a 3rd axis to capture the mouse turning. – Cort Ammon Dec 04 '19 at 04:50
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    Um, how could they possibly do absolute position? GPS onboard?? J/K, GPS doesn't have that much resolution. The mouse simply does not have the sensors to know its absolute position. This will be clearer if you throw away your mouse pad and use any available surface for the mouse. Mice don't actually need mouse pads; they are the fuzzy dice of computers. – Harper - Reinstate Monica Dec 04 '19 at 16:23
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    @Harper-ReinstateMonica - perhaps, but the question was more general and included track balls, which could conceivably produce an absolute position (although why they would I do not know) – Michael Stachowsky Dec 04 '19 at 16:51
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    @Harper-ReinstateMonica, Re, "The mouse simply does not have the sensors..." I guess that depends on what you call a "mouse." I worked with computers that had a thing that we called "the mouse." It fit nicely in the palm of my hand, it had four buttons on top, conveniently close to my finger tips. I used it to push on-screen buttons, and drag things around. But, its "tail," plugged in to the Wacom tablet that it sat upon. Is "mouse" defined by its shape and how you use it? or is "mouse" defined by some particular technology? – Solomon Slow Dec 04 '19 at 20:38
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    "track balls, which could conceivably produce an absolute position" -- How could they, without knowing the size of your displays and their configuration? The mouse informs the computer of its state, but not the other way around. The computer is not going to inform the mouse when a new display is connected/disconnected or when its position changed. You could make a mouse protocol that does, breaking compatibility afforded from pre-existing mice, but it would be much more complex for no benefit. – JoL Dec 04 '19 at 21:00
  • And if range of the absolute coordinates was fixed (i.e. 0% to a 100%), to not need to know information about the displays, it would cause the speed of the mouse to vary depending on the quantity and sizes of the displays. If an N degree horizontal rotation moves the mouse from the left border to the right border of a display, and then you add a new display left of that one, those same N degrees are going to move you from the left of the left display to the right of the right display, doubling the speed of x movement. – JoL Dec 04 '19 at 21:20
  • Also, in that case, because granularity of movement is surely fixed (e.g. can't communicate anything smaller than 1 degree of rotation), the more displays you add or the bigger their size, the larger the steps the mouse would have to make. Eventually, you wouldn't be able to click on stuff because they'd be positioned in between the possible positions that the mouse could take in the displays. – JoL Dec 04 '19 at 21:24
  • Some optical mice used to have a reflective tablet with lines in it so it would have been theoretically possible for them to report absolute position (Although it would have taken more electronics than could fit in the mouse at the time). Now that I think about it--I think that by definition this would have made the thing a tablet and not a mouse. So a mouse is relative by definition, a tablet is absolute by definition (Regardless of how the thing you are holding is shaped) – Bill K Dec 04 '19 at 22:57
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    @JoL I had just that sort of track ball back in the Apple II days. It emulated a joystick instead of a mouse, providing a 256x256 window IIRC. But the stupid thing had a larger internal window. You could easily move "off screen" and get lost. It was the most frustrating thing ever. – Ukko Dec 05 '19 at 15:10
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    The “gridded” mousepads of Sun workstations could not be “absolute” as there was no way to distinguish which of the many lines you were crossing. And the optics of the mouse could detect things other than the lines. A popular prank where I worked was to put someone’s mouse against the screen. A few seconds of CRT scan would fill up the mouse buffer and lock up Solaris until all the pulses were processed. – WGroleau Dec 05 '19 at 15:46
  • @Harper-ReinstateMonica: Today mousemats may be the fuzzy dice of computers, but I don’t think they always were. I remember the mice of my childhood (’80s–’90s) being quite fussy about what surfaces they worked well on — the right combination of evenness/friction (for mechanical mice) or reflectivity (for optical mice) — and in particular, they often didn’t work well on plain desk surfaces, so the consistent well-suited surface provided by a mousemat was definitely of real value. – Peter LeFanu Lumsdaine Dec 06 '19 at 12:04
  • @PeterLeFanuLumsdaine I find the opposite. The newest mice are finicky about surface, because the onboard camera can't register movement on a surface that looks the same, and there's no fixing this. In the old days, when a mouse failed to track, I popped the ball out and cleaned the rollers, solved. Regardless, my point here is to disabuse any notion that mouse pads are digitizers capable of coding absolute position, e.g. With inductive wires laid in them, because OP might think that. – Harper - Reinstate Monica Dec 06 '19 at 12:16
  • Some osu! (a game about mouse accuracy) players do this by putting their tablet pen inside their mouse: https://www.youtube.com/watch?v=xBihPhHy8po – Artikash-Reinstate Monica Dec 11 '19 at 00:10

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The first mouse tracked relative motion along two axes, and as far as I know all standalone mice produced since have followed suit. It would be difficult to build and use a mouse relying on absolute positioning: it would have to track its movement very accurately, with no slippage, or else allow for regular recalibration; as you mention, it would only be usable in a specific area; and it wouldn’t support varying sensitivity (i.e. slow movement being translated at higher resolutions than fast movement).

Even early optical mice, which used specific mouse mats (as used for example on Sun workstations), didn’t track their position on the mat itself, only their relative movement.

There are mouse-like devices which produce absolute coordinates: pucks on graphical digitisers. These are used on large tablets, and are not practical replacements for mice in most cases.

Stephen Kitt
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    If my memory serves me correctly, early mouse protocols (for PCs at least) did not have the concept of reporting absolute positions. So not only would the hardware have been difficult, the communications protocol lacked the very idea. – JdeBP Dec 03 '19 at 21:28
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    Aside from the space the tablet takes up, digitizers make great mice. The "File" menu or whatever is always in the same place on the tablet so you can just move the mouse there and click. –  Dec 04 '19 at 02:26
  • Also note that with absolute positioning, your movement would have to be limited to the size of the mat. Mouse sensitivity would be then calculated as the proportion of screen size and mat size. That wouldn't really work well. – Sulthan Dec 04 '19 at 09:24
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    I think it's pretty obvious a mouse has to work in relative coordinates because you can pick them up and put them down somewhere else. Without some fixed reference point, like a tablet, absolute coordinates can't possibly work. – JeremyP Dec 04 '19 at 09:54
  • The trackpads on the Psion MC200 and MC400 use absolute positioning. – Alex Taylor Dec 04 '19 at 11:01
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    In his parting lecture, Niklaus Wirth (i.e. the guy who brought the first prototype mouse to europe) mentioned that the beauty of the mouse is that the concept still works with a low fidelity device, because the human is compensating for any positioning errors as part of a feedback loop. If the mouse pointer is not were you want it (due to hardware inaccuracy), you just move it a little bit more. On the other hand, graphical digitisers that produce absolute positions must use very accurate (and therefore expensive) hardware. – Georg Patscheider Dec 04 '19 at 11:01
  • A lot more common than that "puck" you linked to would be the CAD Digitizer tablets. They were very common in the CAD industry (which are alluded to in the wiki article but not shown). – JPhi1618 Dec 04 '19 at 18:33
  • @RossRidge I second that. I have used an absolute digitizing tablet as a mouse. The two biggest drawbacks of it that I remember were, (a) finding space for the tablet on my desk, and (b, distant second) managing the garden-hose-like GPIB cable that connected the tablet to the computer cabinet. – Solomon Slow Dec 04 '19 at 20:44
  • A pad is not necessarily a great mouse, because the on-screen pointer can’t tell you where you are getting ready to touch the pad. I found it nearly impossible to write Chinese characters on a trackpad for that reason. – WGroleau Dec 05 '19 at 15:51
  • I worked on GIS systems from around 1987, and we had A0-sized digitising panels on an adjustable easel that you stood up to use. We could digitise electrical cable runs and equipment directly off engineering drawings and Ordnance Survey maps. The package let us set up by just digitising the four corners of the map into corresponding real-world coordinates, and then it interpolated all the on-map points we entered to compensate for shrinkage and skew, and entered them into database as real-world millimetres from the origin somewhere off the UK's south-western corner. – Paul_Pedant Dec 05 '19 at 18:40
  • @JdeBP Early mouse protocols on the PC didn't matter much, because they were proprietary anyway. They self-standardized early on, because absolute positioning just isn't all that useful for most of the ways you used the mouse, especially in text mode and with non-square pixels in graphics mode. And when you want absolute positioning, there's other devices, like light pens, with better ergonomy for that use. – Luaan Dec 06 '19 at 08:14
  • @RossRidge On some operating systems. Not on windows, or any variety of linux that I've used. – Hearth Dec 06 '19 at 14:12
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It was by no means a mass market device, but Hayward and Ramstein's Pantograph (1993) encoded linkage positions as absolute coordinates. It also provided force feedback, and could ‘drive’ itself based on screen contentPantograph

scruss
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  • Of course there have been explicite mass market devices using similar mechanics like this ad from 1983 showing a drawing arm from 1983 for Apple, Atari, Commodore and alike. – Raffzahn Dec 04 '19 at 11:07
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    oh my, that device (a Plot-II graphics table [sic], also sold as the VersaWriter) looks perfectly terrible! Two potentiometers on bendy plastic arms can't be very accurate: at least the disk in the picture's safe from electromagnetic graphics tablets' legendary ability to wipe disks. – scruss Dec 04 '19 at 15:53
  • Back In The Day (tm) I had a robotic plotter that crawled around on a piece of paper, drawing as it went. Hideously inaccurate, to the point of being useless as a plotter - but it was a cool bit of tech. :-) – Bob Jarvis - Слава Україні Dec 05 '19 at 03:58
  • @BobJarvis-ReinstateMonica was it that one from Linear Graphics for the Beeb? I remember those! – scruss Dec 05 '19 at 14:05
  • @scruss: I don't remember who made this thing, but it had a dock that it sat in to which it was connected by a ribbon cable. I would crawl out of its dock and wander around the piece of paper. However, its wheels would slip and spin unless the paper was sufficiently rough, which my paper wasn't, so it would get all messed up. I think it was a Sirius Cybernetics product, because its fundamental design flaws were completely hidden by its superficial design flaws or, in other words, the joy that one got from getting it to do anything made you ignore the fact that it did nothing useful. – Bob Jarvis - Слава Україні Dec 05 '19 at 14:19
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    @scruss: FOUND IT! http://www.computinghistory.org.uk/det/20994/Penman-Robotic-Turtle-Plotter-Printer/ – Bob Jarvis - Слава Україні Dec 05 '19 at 14:23
  • @BobJarvis-ReinstateMonica, like putting a stepper motor on each knob of an Etch-a-Sketch? – WGroleau Dec 05 '19 at 15:53
  • @WGroleau - yes, except you turn the Etch-a-Sketch upside down, turn the knobs at right angles so they become wheels, and before you known it they've taken over the world and killed Kenny. THE BASTARDS!!!!! :-) – Bob Jarvis - Слава Україні Dec 05 '19 at 18:30
  • My friend Mike and I built one of these as a high school science fair project in Syracuse in 1979. A jointed arm with two joints (shoulder and elbow) with a shaft encoder at each joint. Cromemco Z-80. We plotted the coords on the screen using ASCII graphics - super low res. It worked, and we won! So were we the first? Who knows? – GaryO Dec 06 '19 at 19:21
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Some of the HP Omnibook series of laptops and sub-notebooks from the mid 1990s had a curious pop-out “mouse on a stick”:

HP Omnibook 800 Mouse, from 1996 manual

While hardly part of the original mouse timeline dating back to the 1960s, this HP mouse used encoders built into the computer body. The encoders — as shown in this Omnibook repair video from 10' 40" on — appear to track the extension and angle of the mouse stick. In order to produce PS/2 mouse compatible movement counter signals, the (∆r, ∆θ) from the internal encoders would have to be temporarily converted to an absolute (X, Y) position from which (∆x, ∆y) signals were derived.

From memory, the Omnibook mouse would continue to produce (∆x, ∆y) signals if it hit the relevant end stops, so there were perhaps some additional limit switches in the mouse hardware. It was a fairly terrible mouse, and completely unusable by left-handed people.

scruss
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  • What an absolutely odd device. Thanks for showing it off – Michael Stachowsky Dec 04 '19 at 17:48
  • Glad to, @MichaelStachowsky. For a while, HP were very keen on their encoder technology and this device must've gained its designer a great bonus that year as it's likely to use a couple of HP showcase components. Shame the mouse was an ergo-disaster though – scruss Dec 04 '19 at 17:53
  • It might be more useful to readers if you concatenate the answers to give an overview about various technologies - as there are quite some. – Raffzahn Dec 04 '19 at 20:59
  • Left-handed people were obviously not the sort of minority customer HP was interested in courting. Humph! :-) (Full disclosure: I have a left-handed daughter. She has a Mac :-). – Bob Jarvis - Слава Україні Dec 05 '19 at 04:00
  • Looks like a crude version of the old Toshiba/Thinkpad joysticks: https://en.wikipedia.org/wiki/Pointing_stick – Lawnmower Man Dec 05 '19 at 04:51
  • @LawnmowerMan the Trackpoint uses force-sensitive resistors and produces relative output. The charity I work for uses them in its open-source LipSync sip-and-puff mouse. – scruss Dec 05 '19 at 14:02
  • +1 for remembering that one! I used to own one of those laptops, but I totally forgot about the stick mouse. The laptop itself, BTW, was just barely Windows compatible. Not really practical for much else besides editing Microsoft Office documents and maybe checking your mail. (I don't actually remember how/if it connected to the outside world.) – Solomon Slow Dec 05 '19 at 14:12
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    @scruss: re “completely unusable by left-handed people” — I’m left-handed, but habitually use my right hand for mouse/trackpad, and I know plenty of other left-handed people who do the same. – Peter LeFanu Lumsdaine Dec 06 '19 at 12:00
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    @PeterLeFanuLumsdaine Likewise. I even remember that there was a period where I used the mouse left-handed as a child. I can't remember why I switched but I'm guessing it was just less hassle to develop a bit of ambidextry than to have to reconfigure every computer I sat down at. – ssokolow Dec 09 '19 at 08:14
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I am experimenting with a graphics pen and tablet and it got me thinking about the difference between it and my mouse. One huge difference is that the tablet's working area covers the whole screen,

No, that's scaling of your software. The tablet has its own coordinate set, which gets adjusted to your document and/or screen. Usually by the drawing application using it in absolute mode. For screen the driver may be configured to do it, or offer it as relative to fit usual mouse handling.

so that you can tap on an absolute position.

Jo. After all, with a tablet, the detection is not done by the moving device, but the fixed surface.

It's imperative for drawing tablets to work absolute, as for one there's no detected movement when the pen is (way) up. Only absolute detection will work to catch it when going down again. But more importantly, with a mouse a user usually 'homes in' to a target - meaning the movement is controlled via an optic feedback on the screen - while with a tablet the user expects to hit the point like with a pen on paper. No matter how much movement has happened in between.

My mouse always outputs relative x/y from its last position.

In general, without a fixed reference can only detect relative movement. Even a 'simple' device like an odometer only adds up data delivered as relative. And like everything working relative, it adds up errors. Thus relative recording isn't a great idea with tablets anyway, as the user assumes the device to read the exact spot he targets.

This is obviously a huge benefit because it does not restrict the mouse to one part of your desk.

The same can be done for tablets by scaling and panning. Take touch pads for example, here a cursor can be moved several times in one direction by repeated moves. Despite the fact that it delivers absolute coordinates. Similar is done for drawing tablets.

I am wondering if this was how the original mice/trackballs/whatevers did, or were they absolute position?

Always relative. Anything else would be incredibly complex and end up in a system resembling a drawing tablet. There have been combinations that looked like a mouse, but had to be used on a tablet (or with a fitting tablet like sensor setup), but they were incredibly expensive while combining disadvantages of mice and tablets.

For a generic, not very exact input device, relative is the way to go. Even more when the task is about relative positioning anyway.

manassehkatz-Moving 2 Codidact
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Raffzahn
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  • "It's imperative for drawing tablets to work absolute, as for one there's no detected movement when the pen is (way) up. Only absolute detection will work to catch it when going down again." - What? Could you explain this further? It's not at all clear to me why absolute detection is required to resume tracking the stylus after it's left detection range. – 8bittree Dec 11 '19 at 23:09
  • The stylus is not tracked when it's lifted. All the tablet sends is "touch detected at (x, y)" messages that are integrated by the driver over time. Those "(x, y)" are absolute coordinates, or at least relative to some fixed origin of (0, 0). – Stephen M. Webb Jan 18 '24 at 19:57
  • @StephenM.Webb This is not always true but depends on tablet type. Inductive ones can (and do) track pen/puck when lifted. – Raffzahn Jan 18 '24 at 20:20
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The Commodore 1351 mouse, created as an afterthought for the C64 and C128 and (ab-)using those systems' analog paddle inputs to transfer mouse position data (since no mouse support was planned when those computers were designed), maintains an internal sort-of-absolute position on a wrapping 64x64 pixel grid which it then provides to the computer. While mouse-supporting software running on those computers will have to convert those 64x64 grid positions to really absolute values by correcting for the wrapping and optionally applying some sort of acceleration algorithm, this type of mouse does not transfer relative position in terms of signed x/y displacement values.

TeaRex
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  • It's interesting to note that the paddle inputs work by measuring how long it takes an external resistor to charge a capacitance, but the mouse works by waiting a precisely-controlled amount of time after it sees the capacitor discharged before it charges it essentially instantly. As such, it could achieve accuracy that's much better than such inputs should seem capable of supporting. – supercat Dec 06 '19 at 21:20
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As Stephan Kitts mentions, the mouse puts out relative coordinates. In reality the mouse sends its x/y movement (not coordinates) in mickeys (yes that's the name of the unit) to the PC in the form of interupts. The software can intercept these interupts and process them to do whatever: move a cursor, scroll, move an item in a game or more. Not necessarily anything to do with position on a screen. That is only a (now the most common) usage of a mouse.

sijpie
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When I was an older kid or early teen, my uncle took me to his office and let me play around on his computer. It was a dedicated CAD workstation, with a mouse that did actually encode absolute position on its pad (or whatever you would call it). The tail of the mouse was attached in the opposite position from modern mice, coming out under your wrist as you were holding it and plugging in to the "mouse pad" at the bottom, while a second cable connected the pad to the actual computer. At the top of the mouse, where the tail would normally connect, there was instead a crosshair that could be used to select icons that were actually printed on the "mouse pad" itself.

I remember getting frustrated because none of its four buttons were labelled, so you just had to remember which button did something with the mouse cursor on the screen, and which activated the function that the crosshair happened to be pointing at.

This is all from memory from quite a while ago, so I don't really have any more information about it, like a manufacturer or model or anything.

HiddenWindshield
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