Breakfast Bytes Blogs

I was idly watching YouTube over the break when "the algorithm" recommended that I watch a Computerphile video called How the Mouse Works. In some ways, it is a history of the computer mouse. But the history of the mouse goes back a lot further. So I'll dig into the ancient history, and then embed the video at about the point in the history that it picks up.

Light Pens

But I can go back further to about 1971 when I first used a graphics device when I worked at the Cambridge University Engineering Department for some of my time between high school and university. It wasn't color. It was a big monochrome cathode ray tube (CRT) on an Elliot 509 (obscure British) computer. You did have a pointing device though, a light-pen. This could sense when the cathode ray traced over the objects on the screen and thus which object you were pointing at. I think that there was a rudimentary cursor that you could "pick up" with the light-pen and move around, since otherwise there would be no way to point at a blank screen and indicate where you wanted to draw something. It had one button, which was a food-pedal.

Anyway, it is so old that I can't even find a picture of one on the Internet.

The First Mouse

The original mouse was invented by Doug Engelbart at SRI (and was actually built by Bill English). Very few people got to see it until December 9, 1968 when Doug presented what subsequently became known as "The Mother of All Demos". I wrote about it on its 50th anniversary (almost, the anniversary fell on a weekend) in my post The Mother of All Demos.

As I said in that post:

At the beginning of the demo, expectations were low since Doug was regarded as very eccentric. Two hours later, computer science had an agenda that would inspire it and occupy it for decades. Arguably, only now has the full implementation of those ideas spread around the world in the form of the smartphone.

Xerox PARC

The scene now moves up the road to the Xerox Palo Alto Research Center (PARC) and the Alto mice. The Alto was the first machine designed for personal use, with windows, a graphical user interface (GUI), and a mouse. See my post The Alto: The Machine That Changed the World for more details about the Alto, if you don't already know the history.

There were three generations of mice. The third generation was the first optical mouse, invented by Dick Lyon. There is a wonderful historical document The Optical Mouse from that era. Surprisingly, it doesn't seem to have a date.

Before it gets to the optical mouse, this document also has pictures of the earlier generations, the "wheel" mouse, and the "ball" mouse. As you can see in the images, the "wheel" mouse was similar to Engelbart's mouse, with horizontal and vertical wheels. The "ball" mouse was more like the first commercially available mechanical mice, with a ball that rolled on the top of the desk (or more likely on a mousepad) with other wheels inside that captured the horizontal and vertical motion. Without too using much electronics, both mice just sent up, down, left, and right pulses to the Alto that did the work of working out how the mouse was moving and moved the cursor on the screen. Of course, they sent the button state, too.

The big problem with all mechanical mice is that they get gummed up with dirt and need to be cleaned periodically. Also, the ball doesn't always grip perfectly and so the cursor sometimes skitters across the screen annoyingly.

The optical mouse worked on a different principle. Unlike optical mice today, it had to be used on a patterned surface of white background with black circles. Optical sensors were not big enough in that era to just use the texture of the desk as modern mice do. A lamp illuminated the patterned surface, and a tiny bit of optics focused the incoming light onto the unpackaged chip.

This is the chip. You can see how simple it is compared to modern chips. You can clearly see the 4x4 optical sensor array to the top left of the chip (inside the pad ring, of course). At the bottom is a programmable logic array (PLA) that implements the state machine that converts changes in the optical pattern as the mouse moves into the same pulses that the mechanical mice generated. The optical mouse was designed to be compatible with the mechanical mice so that they could be used interchangeably, and the Alto hardware/software did not need to be changed in any way.

I'm not sure if this optical mouse was ever "in production" in the sense that many people used it, or whether Dick just built one and used it himself. He does say in the document that:

A complete optical mouse has been in use for many months, with only one minor problem: when one is forced to use a workstation with an electro-mechanical mouse after becoming accustomed to the optical mouse, the erratic performance is an annoying contrast.

The Video

The Signalling Switch

So the first commercial mice were very like the mechanical Alto ball mouse in that they were mechanical, connected to the computer with a wire (which also delivered power, so the mouse did not require batteries), and just sent the pulse trains as the mouse moved and left the calculation of where that meant the mouse/pointer ended up to the host computer.

Some computers were designed from the beginning for use with a specific mouse like the Mac or the Atari ST. But the IBM PC was designed for a command-line-interface and didn't have a mouse port. So this required a different kind of mouse so that the PC's serial port could be used. These mice required more electronics to convert the pulse train into a few characters and encode them as the serial port expected. Instead of just pulses, the electronics added them up and regularly sent an update as to how fast the mouse was moving vertically and horizontally.

Optical Mice

The next change was to switch from mechanical to optical technology. Sensors were much better than in the Alto era so it was no longer necessary to have a special patterned pad. Despite this, optical mice often work better on a pad, especially if your desktop (the real one, not the one on the screen) is shiny, and you have no chance if you have a glass desktop without something under the optics on which they could get some traction. However, the interface was just the same, so that you could switch from optical to mechanical.

Wireless Mice

Once BlueTooth came along, it was an obvious development to lose the cord. Actually, it wasn't entirely a positive change since the cord was also how the mouse was powered before, so wireless mice required batteries. At first, these were regular batteries, but gradually rechargeable batteries got built into the mice as battery technology developed. In a totally bizarre decision, Apple decided that the recharging port for the mouse should be on the base of the mouse, which means that it is not possible to use the mouse while it is charging!

Buttons

The number of buttons on a mouse has been another subject of discussion. The original Alto mice had three buttons (known as red, yellow, and blue despite being all black, I suspect because that was what graphical trackpads had used (although they had a fourth button, too). The Macintosh famously started with a one-button mouse. Some mice had scroll-wheels, too (which usually is also a button).

Today

On a worldwide basis, most access to the internet is using smartphones. Although they have a graphical user interface, they don't have a cursor and, instead of a mouse, you use your fingertip. There's a sense in which we've come full circle from having graphics, and something to point with (a light-pen), but no mouse to...graphics, and something to point with (your finger), but no mouse.

And if you want to relate mice to time to market, read my post It's the Second Mouse That Gets the Cheese,

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