There are only 3 forms of bit storage, historically.

1) Poking holes in things ( tape, DVD, etc ) 2) Magnets ( core memory, drum memory, tape, disks ) 3) Circuits ( DRAM, NAND, etc )

Examples of all three of these still exist.

What's interesting about XPoint is it is literally a fourth form that has never been commercially available: melting a substance and cooling it quickly or slowly, forming either a crystal or amorphic solid, which then has different properties. We don't know what the substance is, but it's cool that we now have this 4th thing.

> melting a substance and cooling it quickly or slowly, forming either a crystal or amorphic solid, which then has different properties

This is exactly how rewritable optical media works.

There are only 3 forms that really survive to this day. There are a couple of notable obsolete ones:

4) Delay lines. I would definitely not categorize these as circuits. The bits are stored as pressure waves in motion.

5) Electrostatic charge. Talking about the Williams tube. The bits are stored as residual charge on a phosphor surface.

... and magnetic bubble memory, which is a very odd hybrid somewhere between tape and delay lines.

Also, phase-change optical (as in rewritable CDs/DVDs).

Also also, printing stuff out at high bit-density with good ECC, and scanning it back in again.

Also also also, chemically encoded bits (as in the DNA-based storage that was demonstrated recently).

There are more, not in common use or very scalable (e.g., mechanical switches).

I think it's a bit conspicuous how you mention good ECC for printing stuff out, since good ECC is a staple of many forms of storage (especially hard drives, optical drives, tape) and we don't mention e.g. "storing bits on spinning rust with good ECC and reading it back in again".

I think the problem with paper is thot it's not really part of the computer any more. You need a human to take the paper out of the printer, store it, and put it back in the scanner. At least with tape and optical, we have robots to do that for us.

I hadn't thought of that. Your average "crappy thumb drive" probably has more ECC than you'd need on a physical piece of paper. You're right.

Although when crappy thumb drives fail the whole thing tends to be unreadable or doesn't even show up as a USB device.

Generally no amount of ECC will help the default failure mode of these.

Is #5 that much different from dynamic RAM, with bits stored as capacitive charge?

Memristors would technically be another form of storage but after the hype HP have been a bit quiet on this for the last 3 years.

MO drives heated the medium to the Curie point. 3D XPoint isn't all the revolutionary.

Drum memory was still spinning rust, the only difference is the axis of rotation.

My floppies would like to have a word with you.

It lives on in the save icon. But in all seriousness you're right, floppy as a medium for data storage is dead.

Unless you're the US gov. According to Wikipedia: "In May 2016 the United States Government Accountability Office released a report that covered the need to upgrade or replace legacy computer systems within Federal Agencies. According to this document, old IBM Series/1 minicomputers running on 8-inch floppy disks are still used to coordinate "the operational functions of the United States’ nuclear forces..." The government plans to update some of the technology by the end of the 2017 fiscal year." [1]

1. https://en.wikipedia.org/wiki/Floppy_disk#Use_in_the_early_2...

Optical discs are relegated to back shelves too. Hard to beat cheap rewritable nand flash.

ps: I'd be curious about a tiny, 2017 laptop friendly optical disc storage. Say a 2.5" RW BD layer in cartridge. A modern mini disc.

There are people using optical media for long term storage. So I am not counting it out as a storage medium. In my classification I would put it in cold storage tier.

Surely. Although I'd have thought for long time storage magnetic tapes were cheaper.

I doubt anything could be compact enough to be laptop friendly in the sense of being a physical part of the machine - but external USB 3 BD burners are quite small (powered over usb, too), I have a Samsung which works fine.

i don't know, a small radius "may" help remove mecanical constraints, and with a non stacked lens design sdcard reader height device.

I was mostly wonder about the psychological aspect of form factor. naked optical disks are non-personal, mini discs weren't. You interacted with them freely, carried them as is in your pocket. A large enough yet tiny enough reincarnation might be "fun".

On one hand, people complain about government spending. On the other, they complain about government's old equipment.

Floppies are pretty much dead unless you use industrial computers that can't be upgraded.

Floppies are a type of spinning rust.

spinningrust.io the new web 2.0 tech start up that performs data science statistical arbitage techniques on your customer data.

Floppy drives themselves can generally be replaced by emulators, at least from a technical perspective. Like with a FlexiDrive or HxC.

That's not to say it'd always be possible, I presume that there may be regulatory issues in some cases.