A scratch disk is a removable storage device for a computer that is designated to hold information but not for very long. Scratch disks can be used to take files from one computer to another, in the rare case that the disk does not go bad before you get it to its destination.
Disks used to be the size of family-size pizzas. They employed fabulous engineering to minimize contact between the disk platters and air, as disk drives would seize up from a speck of dust or a human hair. Dog hair was out of the question, as disk drives were only located in rooms with cooled, filtered air and no pets.
Given the march of progress, scratch disks went from 8-inchers to 5-inchers, then to 3-inchers — while the march of progress on male enhancement oddly went in the opposite direction. Scratch disks became known as diskettes, disquitoes, and then Diskie Babies. However, they were still notoriously unreliable. In this sense, every disk was a scratch disk. Important stuff used to be stored on three disks: the master, the backup, and the second backup, so that you would usually not lose more than your last two edits.
Scratch disks had a catalog, or cat, listing the information on the disk. If the disk got scratched, some of the information might go missing. However, if the cat got scratched, all of the information would go missing. Such a cat scratch often gave the user cat-scratch fever.
Modern scratch disks
In contrast to desperation to keep sand out of one's scratch disk, one now obtains a sand disk with no moving parts nor exposed surfaces. Sand disks are good for everything from scratch disks to games of skittles. Unreliability is no longer a problem with scratch disks. The problem instead is that there is nowhere to label the disk. This is a minor problem, as most people can remember what they put on it long enough to take it off it, unless the person was around in the days when scratch disks were unreliable, in which case his head has become unreliable. Instead of scratch disks, he will scratch his head. In the 2010s, sand disks used to come in rainbow colors and you could remember that
FOO.TXT was on the sand-colored sand disk. In the 2020s, however, the world became more businesslike and all sand disks looked alike. A more major problem is now determining where one put the scratch disk, a problem that is likewise generational. Dogs are allowed back in the computer room, but you can't very well cut Fido open every time you misplace a scratch disk to see if he ate it.
The sand disk is a thumb drive. Recently, new sand disks have come out, which are more like toenail drives. They are impossible to label and impossible to keep from losing, but so reliable that you now have twenty years to carry it across the room to get that file where it is going. (Except that you probably don't have twenty years.)
The future occurred in the 2010s, and the scratch disk went the way of the album. Young computer users cannot be bothered with media but use wires or even Bluetooth (pictured) to carry files from one computer to another without even realizing they are doing so. In the 2020s, they stopped being concerned with individual files at all, as all their information moved onto The Cloud, where someone else with a Pakistani accent does the job of dealing with the occasional scratched disk. You will not remember what all you moved onto The Cloud, but marketeers, dating services, and the FBI will never forget.