File:Punchcard4.jpg
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Figure 4. Punched Cards Top: The punched card used to process the U.S. Census of 1900 (unlike the card used in 1890) had information printed on it to facilitate visual reading of punched information. In both cases punched holes were round and the card size was 6 5/8 inches by 3 ¼ inches. Bottom: The IBM 80-column card, with rectangular-shaped holes, replaced the then-standard 45-column card in 1928. By the early 1930s, the two additional rows shown here at the top of the card were introduced to facilitate alphabetic coding. The 10 holes punched to the left show how the numbers 0 through 9 were represented. The 52 holes punched to the right show how two holes per column were used to represent the 26 letters of the alphabet. The 80-column card and the earlier 45-column card were both 7 3/8 inches by 3 ¼ inches.
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| current | 18:38, 7 January 2013 | | 1,879 × 1,759 (1.44 MB) | Administrator1 (talk | contribs) | |
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| 16:28, 4 December 2009 |  | 550 × 525 (71 KB) | Nbrewer (talk | contribs) | ||
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