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When I began high school in 1987 all the computers in the lab were Apple IIe desktop computers. A question has haunted me since then:

if you inserted a floppy disk "upside down" the Apple IIe would make a hideous noise like a vacuum cleaner. Why? What a shocking design; it scared the heck out of me as a newb. Was it usual to do that to a user? I never really recovered from that; I was put off computers for the rest of high school.

Why design a computer like that for newbs? I'd never seen a computer before. Even worse, the noise would not end. It would go on for minutes. Who on earth decided to make it like that? I'd fire the design team.

While some floppy drives have a sensor to determine when the head is at the outermost position, the Apple uses four approaches:

1. On startup, it blindly tries to move the head outward about 40 tracks. When the motor hits the end stop it will be unable to move further and will consequently stop. Once the Apple has done this, it will assume the head is at the outermost track.




2. When formatting a disk, the Apple uses the same procedure to force the head to the outermost track.




3. The Apple will keep track of how it has moved the head in and out since it forced it to the end stop, and will thus generally know where it expects the head to be. Because each track of a formatted disk includes markers that identify it, the Apple will generally assume that if it thinks it's on e.g. track 12, and it sees a marker for track 12, then it is in fact on track 12 and it can proceed on that basis.




4. If the Apple is unable to see markers that indicate that it's where it thinks it should be, it will force the head to the outermost track, then step it by the proper number of steps to reach the proper position, and look again.

The noise you heard was from step 4. When trying to access a valid formatted disk, the Apple will generally not need to run the head against the end stop, but the back side of most disks won't typically be validly formatted.

The short answer is they did it to save money. They could have made the drive behave better when a disk is inserted upside down, but that would have required larger ROM chips to store the firmware or more expensive drives and controllers to detect the problem.

As long as it didn't damage the computer such behaviours were considered acceptable to get the price down.

The obvious answer is that it wasn't designed 'for newbs' but as a general purpose personal computer that would find its way into many homes and businesses as well as educational establishments. Even in the latter, they also had to be suitable for running some fairly advanced software as well as for introductory courses.

By the standards of the 70s, when serious computing was generally the realm of the scientifically literate, the Apple II was pretty user friendly though. It actually had a monitor and keyboard, you didn't need to flip switches and look at lights to boot it up, and programming errors gave fairly comprehensible error messages.

It also had to be built to a budget though, so they couldn't design it to prevent every instance of user error from causing problems without the cost ballooning. Apple computers were already relatively expensive for their time and they'd just have priced themselves out of the market if they'd tried. So yes, they probably knew what would happen if you put the disk in upside down, but since it wouldn't break anything permanently it wasn't seen as worth the cost of fixing.

For what it's worth, you could swap in pretty much any other computer from the 70s and 80s and there'd be plenty of other issues where the clumsy interactions of novice users could cause bad things to happen with them.

If you inserted the disk "upside down" the Apple //e would make a hideous noise like a vacuum cleaner.

Not sure what the 'vacuumer sound' should be. could it be that you're refering to the way the drive returns - and calibrates - to track. I would rather describe it as a fast clicking noise over some scratching.

Also, there was no different operation between "upside down" or not. Simply as the drive had no way to detect which was the'right' side (*1). In either case the II tried to read the disk. The difference may eventually have been that there was nothing to read on the back side (of the disks you used), resulting in an endless attempt to read.

There was effectively no room in the 256 byte ROM of the disk controller for a more sophisticated error recovery than to try again and again and again...

Why? To me what a shocking design;

Because it's an awesome simple design. The head ist moved across the racks by a spiraled disk. Turned in one direction the head moves outward toward track 35, when reversed it turns toward track 0. After power up/reset the head may be positioned at any of the tracks. So it needs to move in a way to get to a defined point - with track 0 being a desirable goal.

There is no way to tell on what track it is, so the computer moves the head back toward track 0. Now, they could have installed a sensor telling when track 0 is reached. Except, Woz tried to minimize parts and logic, so he devised a way to do it without a sensor and electronics. So the spiral disk was made in a way that the head simply hits a stop were track 0 is supposed to be. Now the controller can always turn the head back for full 35 tracks. It'll move until it hits the stop. after that the disk continues to move (until all 25 steps are done), but the slider moving the head just jumps the spiral track, as the head can't move anymore.

Splendid solution to solve an enginering problem without any logic, sensors and whatsoever, just a groove in a disk.

it scared the heck out of me as a newb. Was that usual to do that to a user?

Jup.

I never really recovered from that; I was put off computers for the rest of high school.

If it got you off that easy, I guess there where other things for you to enjoy.

Why design a computer like that for newbs?

The computer wasn't designed for 'newbs' at all, it was designed as a computer for general use. A quite cost efficient design, which BTW saved Apple several times from otherwise disastrous failures.

*1 - A fact that many owners used to double their disk capacity - either by adding a second write notch at the opposite side or by adding a Protected/Standard/Unprotected switch to their floppies.