Processing and preservation
Today, most computer users find it hard to imagine life before downloads or compact disc
technology (let alone before floppy discs). But that is the environment into which the new computerised Archive was born.
The first computer storage medium was paper - data were recorded using holes punched into paper tape or punch
cards. The Archive received data in this format for over twenty years and, until 1981, disseminated data to using
paper media - primarily stacks of 80 byte punch cards (users had to take great care not to get their cards 'chewed' by
their card readers and heaven help them if they dropped the stack).
By the late 70s and early 80s, most the Archive's data were backed up on large reels of magnetic tape
holding up to 40 megabytes (MB) of data. Some studies such as the big Government surveys, were also deposited
at the Archives with this media.
Although these tapes were a great improvement on paper technology, they were by no means convenient. They
had to be read from end to end making searches cumbersome and time consuming and, as Ivor Crewe remembers, the
racks upon racks of magnetic tapes that built up made the Archive less than popular with the University of Essex
Computer Department where they were housed.
The Archive began to disseminate data to users on floppy discs in 1981, followed ten years
later by CDs and of course, now most users download the data they need directly from the Internet.
Today, the Archive uses Super Digital Linear Tapes (SDLT) as one of its storage and preservation strategies. These
can hold up to 800 gigabytes (GB) of data - the equivalent of 10,000,000,000 punch cards.
You wouldn't want to drop that stack - laid end to end, they would circumnavigate the world, not just once, but 160 times!
Further details on processing and preservation
over forty years.