![]() Quite complex manipulations, including sorting were possible using these techniques. Combining the cards from two different selections produced a logical or. Using two or more needles produced a logical and function. As the needles were lifted, the cards that were notched in the hole positions where the needles were inserted would be left behind as rest of the deck was lifted by the needles. Instead, they were manipulated by passing one or more slim needles through selected holes in a group of cards. Edge-notched cards, however, were not intended to be read by machines such as IBM card sorters. To allow a visual check that all cards in a deck were oriented the same way, one corner of each card was beveled, much like Hollerith punched cards. More-complex data was encoded using a variety of schemes, often using a superimposed code which allows more distinct categories to be coded than the number of holes available. ![]() For example, one hole might record the answer to a yes/no question on a survey, with the presence of a notch meaning "yes". ![]() The holes were assigned a meaning dependent upon a particular application. To record data, the paper stock between a hole and the nearest edge was removed by a special notching tool. The center of the card might be blank space for information to be written, or contain a pre-printed form, or contain a microform image in the case of edge-notched aperture cards. While there were many variants, by the mid-20th century a popular version consisted of 5-by-8-inch (13 by 20 cm) paperboard cards with holes punched at regular intervals along all four edges, a short distance in from the edges. An early instance of something like this methodology appeared in 1904. Edge-notched cards are a manual data storage and manipulation technology used for specialized data storage and cataloging applications through much of the 20th century.
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