Microfiches are sheets of photographic film on which a large number of pages of information are stored by photographically reducing images of the information. This was a common method of output for computer data, allowing a large quantity of data to be stored in a small and easily stored format. High-density microfiche can store 3000 pages of information on a single 105 x 148mm (4 x 6 inch) sheet of fine-grained film. To read the information, a viewing device with very high magnification and resolution is required, together with a rapid-scan capability.
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