Re: How so?
Message #11 Posted by Frank Wales on 17 May 2006, 1:36 p.m.,
in response to message #10 by Mike
Quote:
I'm surprised that they didn't have a 3.5" disc that didn't have a shutter at all (or did they?).
No; as far as I know, the shutter was a feature of every 3.5" disk design.
Quote:
Or, one that was completely manual, requiring manual movement to open and close it.
Whereas, the first version of the 3.5" was just like this.
Quote:
The use of the word "automatic", seems to reflect an innovation (or change) from a non-automatic version.
Exactly.
The very first Sony/HP 3.5" disks had a metal shutter that the user slid open by hand, and slid closed by hand. There was no mechanism at all inside the first drives to slide the shutter back and forth, since the disks that these replaced in the market were the 5.25" drives which only had sleeves to protect the recording surface of the disk, and any kind of shutter was a big improvement.
However, you can't insert a 5.25" disk into its drive without removing the sleeve, so no-one forgot to do that. But the shutter on the 3.5" disk is a part of it, and enough people got occasionally frustrated with the disks when they forgot to open the shutter first. Consequently, making the shutter open and close automatically was a natural incremental improvement, especially when it became apparent that the 3.5" drive was going to be in the market for a long time. But this improvement required the drive to have a new mechanism internally to engage with the shutter, which introduced a physical compatibility problem with earlier drives, and it would have been commercially stupid to introduce an incompatible design, so this compromise design appeared.
These semi-automatic disks were the engineering solution that smoothed over the transition, since they worked in the newer drives (which didn't push the shutter all the way open, so they could close by themselves upon being ejected), while being manually lockable in the open position for the older drives. This is why, on a manually-opened automatic disk, the hole in the shutter seems too far over compared with the hole in the plastic -- inside an automatic drive, the shutter isn't pushed over so far, so as not to engage with the little locking tab in the corner.
As it happens, these also became a fidget-widget; people would often be found mindlessly opening a disk's shutter, and then gradually squeezing the corner until it snapped shut, only to open it and do the same again over and over to relieve the boredom of a tedious task, such as printing a whole sheet of paper, or writing many thousands of bytes to permanent storage, or talking with a salesman.
There were other changes to the design of 3.5" drives over time too, such as going double-sided, or increasing the information density, but these were all generally introduced in backward compatible ways, so that the newer disks always worked in the older drives.
The only incompatibility I think I remember is that the very first single-sided, single-density drives had trouble if you attempted to format a disk in them that had already been formatted for the later drives (for the longest time, blank disks were *blank* -- the user had to format them first, because of the variety of systems they could be used in). I'm sure someone here who still has a 1983 drive can correct me if I'm wrong about this.
Edited: 17 May 2006, 1:43 p.m.
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