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Many times, I've wished to plug in my backup hard disks into my PC without the risk of any of the data being deleted, overwritten, or modified in any manner. Purely for "inspection" and copying over certain files from it.

But, unlike on the old floppies, there's just no hardware switch anywhere to enable "read-only" mode, or "write-protected mode". Why?

This very simple, mechanical thing was a thing back then, but later, "we" decided that it was unnecessary?

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I'm not entirely sure that this question is on topic, but nonetheless, I suspect it has a simple answer.

Physical write protection mechanisms predate floppy disks. At my school holiday job in the 1980s, my desk had a drawer full of write rings for reels of 9 track tape. If the ring is in place, you can write to the tape.

9 track magnetic tape with write ring

There are certainly flash devices with physical write protection mechanisms. Many older USB drives have them. Memory Stick and SD both have a write protection lock. You can see it on the left-hand side of an SD card.

SD card with lock tab

Micro SD cards don't have them because there's no way to effectively make them "micro". And I suspect that's the main reason why they went out of vogue. Once it became unimportant for one removable medium, many of the rest followerd.

The history of storage is about maximising speed, and minimising size and price. Adding a write protection lock adds to both size and price when devices are very small.

In addition, moving parts wear out faster than devices with no moving parts. Unlike disks or tape, flash memory has no moving parts by default. Adding a write protection lock means adding a moving part, which effectively shortens its usable life.

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  • $\begingroup$ There is a SCSI command for write protecting a device, but I am not sure whether that made it into the subset of the SCSI Command Set that is used by the USB Storage Device Class. $\endgroup$ Feb 5 at 7:01

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