![[punchcard]](pcard1.jpg)
This Web page last updated dated Oct 22 2012
I normally sell and provide tech info on old floppy drives and diskettes. Someone in 2012 asked me for some sample diskettes, and a punched card. Someone else asked about punched paper tapes. So I decided to add "IBM cards" and "punched tapes" to my "sample" inventory. More info is below. To order a few, follow this link. To contact me and for general ordering information follow this link.
Punchcards were in use for most of the 20th century to accumulate and store data. They were an inexpensive media that was reliable, decades at a time. They could be filed with or as documents themselves. They were attached to documents or artifacts, or artifacts were attached to them (microfilm for instance). Physically, they are about the size of a "greenback", an early 20th century US paper currency note - 7-3/8" by 3-1/4". Data is (usually) encoded by a "Hollerith card code" of 80 columns of data, each column of 12 positions vertically as one datum (data point, value). The photo shows a card repeatedly punched with the letters A-Z ascending from left to right. Roughly 143 cards make a one-inch stack.
Punched cards date back to weaving looms of the 19th century, which were controlled by holes punched in cards, strung together. Herman Hollerith developed a machine system of punchcards for the US Census Bureau for the 1890 census. Machines could "tabulate" or read the holes and sort the cards - the data in the columns. Without this innovation, the 1890 census would not have been processed until after the 1990 census! Hollerith's company was part of the company which became IBM in 1924. The term "IBM card" became synomonous with "punchcard" in this format, for much of the history of their use; but other companies made cards in other formats.
Their use declined in the last quarter of the 20th century, as other data storage and transfer media became available and inexpensive; and as computing shifted from large mainframes to minicomputers to microcomputers (personal computers). But there's still machines in use which depend on punched cards, and still some datasets around in that format. The US presidential election in 2000 pivoted on votes cast in Florida, as (non-IBM) punched cards with "swinging chad" as not-quite-punched but human-contestable votes.
Rolls of paper tape with punched holes, were used for decades in the 20th as a way to store information. "Numeric control" factory equipment was driven by data on punched tapes, to operate machinery. Typewriters (mechanical printers with mechanical keyboards) could produce and punch codes in paper tapes, to shift from upper to lower case (the print mechanism would literally SHIFT up or down) and to print letters. Teletypes were printers and keyboards which used a mix of electronics and logic, to send and receive data on pairs of wires - they also used paper tapes.
Not long after computers were developed in the 40's, they read and punched paper tapes. Some were used to produce paper tapes for those numeric-control machines. Or paper tapes were used to store data and programs. Minicomputers of the 1960's and 70's, and microprocessor based computers of the mid-1970's, used these too, until other means of storage became available.
Paper tapes in the last half of the 20th century were either 1-inch wide and were punched with 8 bits of data (plus a tiny feedhole), or 11/16" wide and used 5 holes plus feedhole. Most 8-bit tapes encoded textual data in ASCII; most 5-bit tapes encoded Baudot.
These histories are far from complete; search the Web for further information. Contact me if there are any errors in the above. - Herb Johnson
Copyright © 2012 Herb Johnson