I've used the term 'Filing Systems' to describe Acorns Cassette, Disk and Networking systems even though you'd be hard pressed to call the very basic cassette load and save of the System 1 a Filing system and of course the Networking system, Econet, does much more than just provide a filing system.
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The earliest of Acorn's computers only had the facility to save and load programs (files) to and from compact cassette. The System 1 provided only a very basic facility in the Monitor program contained in the machine's PROMs. The follow on System 2's Cassette Operating System, COS, provided a much improved cassette storage capability.
Again in the early days of Acorn Computers floppy disks were really only available to education or commercial users (or very well off hobbyists) because of their prohibitive costs, in 1979 a single floppy disk drive cost almost £400, about £2000 in todays money ! The Acorn System 3 was provided with a Disk Operating System, DOS which supports 5.25" floppy disks via an Intel 8271 controller. This same DOS was used in the later Atom Computer and of course its legacy continued in the BBC Computer.
Econet was Acorns networking solution, it provided a low cost, simple to set-up networking capability which was widely used by schools and colleges, it enabled the sharing of expensive disk storage and printers between many individual computers e.g. in a classroom. It seems to have started life connecting Atom Computers sharing a System 3 File Server but was supported by all their later machines as well.
Acorn System Computers never moved beyond Floppy Disks however Winchester Disks did become available for the BBC/Master Computers and were also used on their FileStore. I have included some information on these products here.