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Alongside the punched card, paper tape remains fixed in the public mind as symbolic of mid-20th century computing. Developed as storage for teletypes — huge electromechanical devices that were a cross between a typewriter and a telegraph — paper tape came in variable length and could thus store variable amounts of data.
Like punched cards, the holes in the tape triggered optical sensors which turned the patterns in the paper or plastic back into electrical symbols, 5 bits at a time.
One of the most famous uses of paper tape was in Colossus, the reprogrammable electronic computer used by Bletchley Park to crack high-level German codes in the second world war. By replacing the usual mechanical sprocket synchronisation with an optical method, the machine could ingest data from paper tape at a highly respectable 5,000 characters per second. Although the electronics was capable of more, at higher speeds the paper disintegrated.
Paper tape's last hurrah was among radio amateurs, who used it to control radioteletypes until the all-conquering microprocessor saw them off in the mid-1980s.
Photo credit: Rupert Goodwins