Hey, a nice company used to send me those in the mail, about one a week.
The same company that used to send me free floppy disks? I was mildly annoyed when AOL switched to CDs, because I could at least erase and re-use the floppies.
There was that annoying interval between that and CDs when the floppy disks came with no write-enable tab, which meant you had to tape over the sense hole to erase and rewrite it.
How much did AoL think they saved by using “non-rewritable” floppy disks? 
Isn’t that more like “how they’ve shrunk”?
I have always liked to build stuff, including electronics. Not so long ago I used a little microcontroller; it had 512 bytes of RAM and 8k of program memory. The point is that the entire system, not a single flip-flop or something, was on an 8-pin DIP, and roughly speaking all you have to do is program it, add power, and it’s ready to go— no need for ancilliary components.
In computer technology, “growth” is shrinkage. That’s what Moore’s Law was about: you double the number of transistors by halving their size. (Ok, not literally, more like making them 71% of the previous generation’s size.)
Likewise, shrink the size of any computer feature and you can pack in more capability in the same weight and space, or even less weight or space.
[George Costanza] I was in the pool! Moore’s law! [/George Costanza]
You ain’t seen anything like the analog computer I was chief operator if for about a year in 1955-56. It occupied 7 consoles each about a yard wide and 7 feet tall. It was built to solve chemical rate equations. The general form consisted of simultaneous differential equations of the form
dx_i/dt = \sum_{j=1}^n c_{ij}x_j+\sum_{j,k=1,1}^{n,n}d_{ijk}x_jx_k
Here x_i represents the quantity of one of the chemicals and the c’s and d’s are rate constants. In practice the machine was limited to 7 chemicals (mostly enzymes) and nearly all the rate constants were 0. Electronic multiplication of voltages was a real bear since it is non-linear and it was done using a real trick. My job was mostly figuring out which vacuum tubes had burnt out and replacing them. As soon as Penn got a Univac I, the analog computer was retired and replaced by a bunch of programmers.
It’s easier to build a device that squares a number rather than multiplies it. Adding is easy. So, compute this:
(A+B)(A+B) - (A-B)(A-B)
Which expands to:
(A^2+2AB+B^2) - (A^2 - 2AB + B^2) = 4AB
Multiply by 0.25 (easy for fixed ratios) and you get the AB you wanted.
That was the trick that was used. A square wave was created that varied between A+B at the top and A-B at the bottom and put through a circuit that squared the voltage. The difference between the top and bottom of the output represented 4AB. But squaring was itself difficult. It was done using a circuit built from “diode switches” which were 3 terminal devices, call them a, b, c that passed current between a and b only when c was positive and it was arranged that the number of these switches that were “on” was proportional to the input voltage. So it approximated du/dx = x or u=x^2/2. I never really understood how this worked, but it did.
I found this:
Page 16 has the diagram. Doesn’t seem too bad; as you mention, it uses diodes as a switch, since they only conduct above a certain voltage. You could create any function you wished with this method, though you’d potentially need a lot of devices.
I was a BSEE student just as microprocessors were becoming widely available. One of our class options was to buy a Motorola MEK6800D2 development kit. Oh! The fun of eight-bit programming, even lacking multiplication. The development board was kind of cool, with a hex-style keypad and six seven-segment LEDs that you could program, and a blank breadboard area. It was a kind of fun to play with, but I didn’t have access to an assembler so every program had to be hand-entered in hex on the keypad. I had grand plans to add a keyboard and a video display card, but just couldn’t get the parts to work together. Seeing prices for these vintage items on eBay make me regret trashing it all in one of our household moves.