Magnetic tape filesystem
Nico de Jong
nico at farumdata.dk
Mon Feb 9 13:03:17 CST 2015
> All this talk about magtapes brought some memories to the fore.
> While a single tape drive was the rule for personal computers, it
> certainly wasn't that way for mainframes. In particular, one very
> important aspect was sorting (and, by extension, merging). The wonder of
> a polyphase (or better yet, oscillating) sort running on a bank of 8 300
> ips drives was mesmerizing.
> Undoubtedly, the folks before me who spent their time shuttling trays of
> punched cards around an IBM 082 have a similar reaction to the "easiness"
> of tape sorts as compared to card sorts...
I remember a regular job (every week....) in my servicebureau where I had to
sort about 40.000 200-byte records on a DOS machine. DOS did have a SORT
command, but it was horribly insufficient.
I therefore had to get back to my experience as IBM 82 operator (!), and do
it more or less that way. The first stop was to create x files, each
containing about 1000 key fields. When the input was read, I would sort one
keyfile at a time internally and write it to a new file. After the sorting,
I merged two indexfiles and write a new file, etc. When all indexfiles were
merged into one, I found the respective full records, and wrote the output
It took about 15 minutes or so for the whole job, but the customer was
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