Science Fair Project Encyclopedia
Key punch
A key punch is a machine for manually entering data onto punch cards. The key punch looked like a small desk. It had a keyboard similar to a typewriter and hoppers for blank and punched cards. Later model key punches printed the value of each column punched at the top of the card. In some cases decks of punched cards were then sent to a second machine called a verifier, which looked a lot like a key punch. Its operator entered the exact same data as the keypuncher, but the verifier machine merely checked to see if the data was the same. Valid cards had a small notch punched on the right hand edge.
Key punch machines could be programmed by wrapping a specially punched IBM card around a small metal drum. The patterns of holes on the drum card could control tabbing and automatic duplication of fields from the previous card, among other things.
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Post-WW II IBM Key punches for 80-column cards
IBM 024
Basic keypunch with no printing.
IBM 026
This key punch could print the encoded character above each column. There were two popular versions with slightly different character sets. The scientific version printed parentheses, equal sign and plus sign in place of four less frequently used characters in the commercial character set: percent, lozenge, pound, and ampersand.
IBM 029
Introduced with System 360, the 029 had new character codes for parentheses, equal and plus as well as other new symbols used in the EBCDIC code. The '029 also printed on the top of the card the punched character. The character was printed using a 5x7 dot matrix array of wires; the ROM from which it derived the shape of the character was actually a metal plate with hundreds of strategically placed pins. By correctly positioning the plate and pressing it against one end of the array of printing wires, only the correct wires were pressed against the ribbon and then the punched card.
The '029 made a distinctive "chunk, chunk" sound as characters were punched.
For applications that required the filling-in of specific fields within the punched cards, the machine could be programmed (using another punched card, of course) to automatically advance to the beginning of each field, only accept certain character types within the field, copy a template card, and so on.
IBM 129
Transistorized key punch with many more features
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