Images: ; CLICK to enlarge.
Left to right: The circuit-closing press ("card reader"); diagram of press; hand insertion of card into a sorter compartment that opened automatically based on the values punched into the card; tallying the day's results. "Each completed circuit caused an electromagnet to advance a counting dial by one number. The tabulator's 40 dials allowed the answers to several questions to be counted simultaneously. At the end of the day, the total on each dial was recorded by hand and the dial set back to zero ."
This apparatus works unerringly as the mills of the gods, but beats
them hollow as to speed.
–The Electrical Engineer, 11 Nov 1891.
The 1890 tabulator was capable only of counting. Subsequent models, developed by Hollerith himself, were also able to add, thus broadening their scope to accounting, warehousing, and shipping applications. Between 1902 and 1905, Hollerith also developed an automatic card feed and a method for reading cards in motion and settled on a standard card format. In 1928, IBM produced its first tabulator (the Type IV) with both addition and subtraction capability.
Left: The Pantographic card punch in operation. The operator holds the stylus over the template. The card is in the punch station above the template. Right: After the cards are punched, they are fed into the Hollerith tabulators.
Above: A punch-card template from a Pantographic punch used the 1890 US census (image: US Library of Congress). Notice there are 12 rows (as in modern punch cards), of which only the bottom 10 were used, and only 20 columns; the curved shape is due to the Pantographic mechanism, an early ergonomic device allowing operators to punch 500 cards per day with good accuracy and minimal physical strain (compared to the handheld "train conductor" punches used in previous trials, which could cause near paralysis with prolonged use -- carpal tunnel syndrome did not start with PCs! -- and with which correct placement of holes was problematic). The Pantographic punch operator positioned a stylus over the desired hole in the template and pressed it to punch a hole in the corresponding position of the rectangular card. The template has areas marked off for various demographic categories.
Above: The "reading board" for a punched card from the 1890 census (the cards themselves were blank; this is like the "decoder ring" for the holes, which itself needs a second "decoder ring" to decipher the alphanumeric codes). Cards had one one corner cut diagonally to protect against upside down and/or backwards cards that might not otherwise be detected and the reading board had the same cut for obvious reasons (image from ). The card measures 3.25 by 7.375 inches, the same size as the 1887 US paper currency because Hollerith used Treasury Department containers as card boxes (pictures not actual size, but all to the same scale):
US banknotes were reduced in size by 20% to their present dimensions in 1928:
Using round holes, the card column density eventually reached 45 prior to the 1928 80-column rectangular-punch standard. Here is the modern (or at least, final) standard, corner-cut, 80-column general-purpose IBM punch card, introduced in 1928, and popularly known as the "IBM card":
Holes in the 80-column card are rectangular, rather than round as in earlier models. The bottom ten rows are labeled with digits; the top two rows are unlabeled and are used in an alphanumeric character code first standardized (by IBM) in 1931 as BCDIC, a 40-character set that included digits, uppercase A-Z, space, minus sign, asterisk, and ampersand , eventually expanded to a large family of 256-character Extended BCDIC (EBCDIC) codes, IBM's Country Extended Code Pages. This type of card was a mainstay of data processing and computing from 1928 through the 1980s and was still in use in voting machines through the 2000 USA presidential election, in which they were discredited when the number of swing ballots might have been less than the number questionably-punched cards and therefore contested ballots (we'll never know, since they weren't counted). Although the poorly punched cards were due primarily to unmaintained machines (many of them more than 40 years old), most localities resolved to replace punched-card technology with something more modern, like optical scanners. Whether the new technology is more reliable, accurate, cost effective, durable, and resistent to fraud and tampering is a concern, but there is apparently no going back.
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|Columbia University Computing History||Frank da Cruz / email@example.com||This page created: January 2001||Last update: 17 April 2021|