Punched card input/output

From Wikipedia, the free encyclopedia
Jump to: navigation, search
An IBM 80-column punched card of the type most widely used in the 20th century
IBM 1442 card reader/punch for 80 column cards

A computer punched card reader or just computer card reader is a computer input device used to read executable computer programs and data from punched cards under computer control. A computer card punch is a computer output device that punches holes in cards under computer control. Sometimes computer card readers were combined with computer card punches and, later, other devices to form multifunction machines.

Most early computers, such as the ENIAC, and the IBM NORC, provided for punched card input/output.[1] Card readers and punches, either connected to computers or in off-line card to/from magnetic tape configurations, were ubiquitous through the mid-1970s.

Punched cards had been in use since the 1890s; their technology was mature and reliable. Card readers and punches developed for punched card machines were readily adaptable for computer use.[2] Businesses were familiar with storing data on punched cards and keypunch machines were widely employed. Punched cards were a better fit than other 1950s technologies, such as magnetic tape, for some computer applications as individual cards could easily be updated without having to access a computer.

Operation[edit]

The standard measure of speed is cards per minute, abbreviated CPM: The number of cards which can be read or punched in one minute. Card reader models vary from 300 to around 2000 CPM.[3] If all columns of an 80 column card encode information this translates to approximately 2500 characters per second (CPS).

Cards may be read using mechanical brushes that make an electrical contact for a hole, and no contact if no punch, or photoelectric sensors that function similarly. Timing relates the signals to the position on the card. Cards may be read serially, column by column, or in parallel, row by row.

Card punches necessarily run more slowly to allow for the mechanical action of punching, up to around 300 CPM or 400 characters per second.[4]

Some card devices offer the ability to interpret, or print a line on the card displaying the data that is punched. Typically this slows down the punch operation. Many punches read the card just punched and compare its actual contents to the original data punched, to protect against punch errors. Some devices allow data to be read from a card and additional information to be punched into the same card.

Readers and punches include a hopper for input cards and one or more stackers for cards read or punched. A function called stacker select allows the controlling computer to choose which stacker a card just read or punched will be placed into.

Card readers/punches[edit]

CDC[edit]

Documation[edit]

Documation Inc., of Melbourne, Florida, made card readers for minicomputers in the 1970s:

  • M-200 card reader, 300 cards/minute[5] also sold by DEC as the CR-11 card reader for the PDP-11[6]
  • M-600 card reader, 600 cards/minute
  • M-1000-L card reader 1000 cards/minute[7]

IBM[edit]

See also List of IBM products#Punched card and paper tape equipment

References[edit]

  1. ^ Stern, Nancy (1981). From ENIAC to UNIVAC: An Appraisal of the Eckert-Mauchly Computers. Digital Press. p. 50. ISBN 0-932376-14-2. 
  2. ^ The IBM 711 Punched Card Reader's card-feeding mechanism was similar to the IBM 402's card-feeding mechanism
  3. ^ Roy, Gautam (2007). Computer Studies for Engineering Students. Mumbai, IN: Allied Publishers Limited. p. 10. ISBN 979-81-8424-211-8. Retrieved July 28, 2016. 
  4. ^ IBM Corporation (1971). IBM 3505 Card Reader and IBM 3525 Card Punch Subsystem. Retrieved July 28, 2016. 
  5. ^ Documation M-200 Card Reader Manual, 1972
  6. ^ Documation M-200 photo
  7. ^ Documation M1000L Card Reader

See also[edit]

Punched card equipment[edit]