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A punch card or '''punched card''' (or '''punchcard''' or '''Hollerith card''' or ''IBM card''), is a piece of Stiff Paper that contains digital information represented by the presence or absence of holes in predefined positions. Now almost an Obsolete Recording Medium , punched cards were widely used throughout the 19th century for controlling Textile Looms and through the 20th century in Unit Record Machines for input, processing, and Data Storage . Early Digital Computer s used punched cards as the primary medium for input of both Computer Program s and Data , with offline Data Entry on Key Punch machines. Some Voting Machine s have used punched cards. HISTORY .]] Punched cards were first used around 1725 by ---> From the 1900s, into the 1950s, punched cards were the primary medium for data entry, checks and savings bonds. During the 1960s, the punched card was gradually replaced as the primary means for Data Storage by Magnetic Tape , as better, more capable computers became available. Punched cards were still commonly used for data entry and programing until the mid-1970s when the combination of lower cost Magnetic Disk Storage , and affordable Interactive Terminals on less expensive Minicomputer s made punched cards obsolete for this role as well. However, their influence lives on through many standard conventions and file formats. The terminals that replaced the punched cards displayed 80 columns of text in Text Mode , for compatibility with existing software. Some programs still operate on the convention of 80 text columns, although fewer and fewer do as newer systems employ Graphical User Interface s with variable-width type fonts. Today, punched cards are obsolete outside of a few Legacy System s and specialized applications. CARD FORMATS The early applications of punched cards all used specifically designed card layouts. It wasn't until around 1928 that punched cards and machines were made "general purpose". The rectangular, round, or oval bits of paper punched out are called Chad (recently, ''chads'') or ''chips'' (in IBM usage). Multi-character data, such as words or large numbers, were stored in adjacent card columns known as fields. A group of cards is called a ''deck''. One upper corner of a card was usually cut so that cards not oriented correctly, or cards with different corner cuts, could be easily identified. Cards were commonly printed so that the row and column position of a punch could be identified. For some applications printing might have included fields, named and marked by vertical lines, logos, and more. The most common printed punched card was the IBM 5081. Indeed, it was so common that other card vendors used the same number (see image at right) and even users knew its number. In addition to punching, printing, and handwriting, there were other methods used to record information on punched cards. Two examples were:
Hollerith's punch card formats The punched card Herman Hollerith patented on June 8 , 1887 and used with mechanical tabulating machines in the 1890 U.S. Census , was a piece of cardboard about 90 mm by 215 mm (the same size as 1887 US paper currency), with round holes and 24 columns. This card can be seen at the Columbia University Computing History site. Columbia University Computing History: Hollerith 1890 Census Tabulator Hollerith's 45 column punched cards are illustrated in Comrie's ''The application of the Hollerith Tabulating Machine to Brown's Tables of the Moon''.Plates from: 1 UNIVAC 90-character punch card format |
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