Unit record equipment
Starting at the end of the nineteenth century, well before the advent of electronic computers, data processing was performed using electromechanical devices called unit record equipment, electric accounting machines (EAM) or tabulating machines. Unit record machines came to be as ubiquitous in industry and government in the first two-thirds of the twentieth century as computers became in the last third. They allowed large volume, sophisticated, data-processing tasks to be accomplished before electronic computers were invented and while they were still in their infancy. This data processing was accomplished by processing punched cards through various unit record machines in a carefully choreographed progression. This progression, or flow, from machine to machine was often planned and documented with detailed flowcharts that used standardized symbols for documents and the various machine functions. All but the earliest machines had high-speed mechanical feeders to process cards a rates from around 100 per minute, to 2,000 per minute, sensing punched holes with mechanical, electrical, or, later, optical sensors. The operation of many machines was directed by the use of a removable plugboard or control panel. Initially all machines were manual or electromechanical. The first use of an electronic component was in 1940 when a gas triode vacuum tube replaced a relay in an IBM card sorter. Electronic components were used on other machines beginning in the late 1940s.
The largest supplier of unit record equipment was IBM and this article largely reflects IBM practice and terminology.
In the 1880s Herman Hollerith invented the recording of data on a medium that could then be read by a machine. Prior uses of machine readable media had been for lists of instructions (not data) to drive programmed machines such as Jacquard looms and mechanized musical instruments. "After some initial trials with paper tape, he settled on punched cards [...]". To process these punched cards, first known as "Hollerith cards" he invented the keypunch, sorter, and tabulator unit record machines. These inventions were the foundation of the data processing industry. The tabulator used electromechanical relays (and solenoids) to increment mechanical counters. Hollerith's method was used in the 1890 census and the completed results were "... finished months ahead of schedule and far under budget". The company he founded in 1896, the "Tabulating Machine Company" (TMC), was one of four companies that merged to form "Computing Tabulating Recording Company" (CTR), later renamed "International Business Machines" (IBM). IBM manufactured and marketed a variety of unit record machines for creating, sorting, and tabulating punched cards, even after expanding into computers in the late 1950s.
Following the 1900 census a permanent Census bureau was formed. The bureau's contract disputes with Hollerith led to the formation of the Census Machine Shop where James Powers and others developed new machines for part of the 1910 census processing. Powers left the Census Bureau in 1911, with rights to patents for the machines he developed, and formed the Powers Accounting Machine Company. In 1927 Powers' company merged with the Remington Typewriter Company and Rand Kardex Company to form Remington Rand. In 1919 Fredrik Rosing Bull, after examining Hollerith's machines, begins developing unit record machines for his employer. Bull's patents were sold in 1931, constituting the basis for Groupe Bull.
Punched card technology soon developed into a powerful tool for business data-processing with a variety of general-purpose unit record machines from these, and other, competing companies.
- 1884: Herman Hollerith files a patent application titled "Art of Compiling Statistics"; granted U.S. Patent 395,782 on January 8, 1889.
- 1890: U.S. Census is tabulated using equipment built by Hollerith
- 1896: 'Tabulating Machine Company founded by Hollerith
- 1901: Hollerith Automatic Horizontal Sorter
- 1902: The Tabulator Limited was formed to sell Hollerith's machines. In 1909 renamed as British Tabulating Machine Company (BTM).
- 1906: Hollerith Type I Tabulator, the first tabulator with an automatic card feed and control panel.
- 1910: Tabulators built by the Census Machine Shop print results.
- 1911: Computing Tabulating Recording Company (CTR) formed by the merger of the Tabulating Machine Company and three other companies. In 1924 renamed International Business Machines (IBM).
- 1911: James Powers forms Powers Tabulating Machine Company, later renamed Powers Accounting Machine Company. Powers had been employed by the Census Bureau to work on tabulating machine development and was given the right to patent his inventions there. The machines he developed were mechanical, as opposed to Hollerith's electromechanical products.
- 1914: Thomas J. Watson hired by CTR.
- 1914: CTR produces 2 million punched cards per day.
- 1914: The first Powers printing tabulator.
- 1915 Powers Tabulating Machine Company establishes European operations through the Accounting and Tabulating Machine Company of Great Britain Limited, in 1929 renamed Powers-Samas Accounting Machine Limited (Samas, full name Societe Anonyme des Machines a Statistiques, had been the Power's sales agency in France, formed in 1922). The informal reference "Acc and Tab" would persist.
- 1919: Fredrik Rosing Bull, after studying Hollerith's machines, constructs a prototype 'ordering, recording and adding machine' (tabulator) of his own design. About a dozen machines were produced during the following several years for his employer.
- 1920: BTM begins manufacturing its own machines, rather than simply reselling Hollerith equipment.
- 1920: The first CTR printing tabulator, the Hollerith Type 3.
- 1921: Powers-Samas develops the first commercial alphabetic punched card representation.
- 1922: Powers develops an alphabetic printer.
- 1927: Powers Accounting Machine Company merges with Remington Typewriter Company, Rand Kardex and others, to form Remington Rand.
- 1928: The first IBM tabulator that could subtract, the IBM Type IV tabulator. IBM begins its collaboration with Benjamin Wood, Wallace John Eckert and the Statistical Bureau at Columbia University. Leslie Comrie described the use of punched card equipment for interpolating tables of data. The IBM 80-column card.
- 1930: The Remington Rand 90 column card, offering "more storage capacity [and] alphabetic capability"
- 1931: Groupe Bull founded, as H.W. Egli - Bull, to capitalize on the punched card technology patents of Fredrik Rosing Bull. Reorganized in 1933 and renamed Compagnie des Machines Bull, the current Groupe Bull.
- 1931: H.W.Egli - BULL Tabulator model T30 introduced.
- 1931: The first IBM punched card machine that could multiply, the IBM 600 Multiplying Punch. IBMs first alphabetical accounting machine - although not a complete alphabet, the Alphabetic Tabulator Model B was quickly followed by the full alphabet ATC.
- 1931: The term "Super Computing Machine" is used by the New York World newspaper to describe the Columbia Difference Tabulator, a one-of-a-kind special purpose tabulator-based machine made for the Columbia Statistical Bureau, a machine so massive it was nicknamed "Packard". The Packard attracted users from across the country: "the Carnegie Foundation, Yale, Pittsburgh, Chicago, Ohio State, Harvard, California and Princeton."
- 1933: IBM introduces removable control panels.
- 1934: IBM renames Tabulators as Electric Accounting Machines.
- 1935: BTM Rolling Total Tabulator introduced.
- 1937: The first collator, the IBM 077 Collator "By 1937 [...] IBM had 32 presses at work in Endicott, N.Y., printing, cutting and stacking five to 10 million punched cards every day."
- 1938: Powers-Samas multiplying punch introduced.
- 1940: First use of electronics in IBM unit record equipment - a gas triode vacuum tube replaces a relay on the card sorter.
- 1941 Introduction of Bull Type A unit record machines based on 80 column card.
- 1943: "IBM had about 10,000 tabulators on rental [...] 601 multipliers numbered about 2000 [...] keypunch[es] 24,500".
- 1946: The first IBM punched card machine that could divide, the IBM 602, was introduced. Unreliable, it "was upgraded to the 602-A (a '602 that worked') [...] by 1948". The IBM 603 Electronic Multiplier was introduced, "the first electronic calculator ever placed into production.".
- 1948: The IBM 604 Electronic Punch. "No other calculator of comparable size or cost could match its capability".
- 1949: The IBM 024 Card Punch, 026 Printing Card Punch, 082 Sorter, 403 Accounting machine, 407 Accounting machine, and Card Programmed Calculator (CPC) introduced.
- 1952: Bull Gamma 3 introduced. An electronic calculator with delay-line memory, programmed by a connection panel, that was connected to a tabulator or card reader-punch. The Gamma 3 had greater capacity, greater speed, and lower rentals than competitive products.
- 1952: Remington Rand 409 Calculator (aka. UNIVAC 60, UNIVC 120) introduced.
By the 1950s punched cards and unit record machines had become ubiquitous in academia, industry and government. The warning often printed on cards that were to be individually handled, "Do not fold, spindle or mutilate", became a motto for the post-World War II era (even though many people had no idea what spindle meant).
With the development of computers punched cards found new uses as their principal input media. Punched cards were used not only for data, but for a new application - computer programs, see: Computer programming in the punched card era. Unit record machines therefore remained in computer installations in a supporting role for keypunching, reproducing card decks, and printing.
- 1955: IBM produces 72.5 million punched cards per day.
- 1958: The "Series 50", basic accounting machines, was announced. These were modified machines, with reduced speed and/or function, offered for rental at reduced rates. The name "Series 50" relates to a similar marketing effort, the "Model 50", seen in the IBM 1940 product booklet.
- 1959: The IBM 1401, internally known in IBM for a time as "SPACE" for "Stored Program Accounting and Calculating Equipment" and developed in part as a response to the Bull Gamma 3, outperforms three IBM 407s and a 604, while having a much lower rental That functionality combined with the availability of tape drives, accelerated the decline in unit record equipment usage.
- 1960: The IBM 609 Calculator, an improved 608 with core memory. This will be IBMs last punched card calculator.
Many organizations were loath to alter systems that were working, so production unit record installations remained in operation long after computers offered faster and more cost effective solutions. Specialized uses of punched cards, including toll collection, microform aperture cards, and punched card voting, kept unit record equipment in use into the twenty-first century. Another reason was cost or availability of equipment: for example in 1965 an IBM 1620 computer did not have a printer as standard equipment, so it was normal in such installations to punch printed output onto cards, using two cards per line if required and print these cards on an IBM 407 accounting machine and then throw the cards away.
- 1969: The IBM System/3, renting for less than $1,000 a month, the ancestor of IBM's current midrange computer product line, aka. minicomputers, was aimed at new customers and organizations that still used IBM 1400 series computers or unit record equipment. It featured a new, smaller, punched card with a 96 column format. Instead of the rectangular punches in the classic IBM card, the new cards had tiny (1 mm), circular holes much like paper tape. By July 1974 more than 25,000 System/3s had been installed.
- 1971: The IBM 129 Card Data Recorder (keypunch and auxiliary on-line card reader/punch) is the last, or among the last, 80-column card unit record product announcements (other than card readers and card punches attached to computers).
- 1975 Cardamation founded, a U.S. company that supplied punched card equipment and supplies until 2011.
- 1976: The IBM 407 Accounting Machine was withdrawn from marketing.
- 1978: IBM's Rochester plant made its last shipment of the IBM 082, 084, 085, 087, 514, and 548 machines. The System/3 was succeeded by the System/38.
- 1980: The last reconditioning of an IBM 519 Document Originating Punch.
- 1984: The IBM 029 Card Punch, announced in 1964, was withdrawn from marketing.
- 2010: A group from the Computer History Museum reported that an IBM 402 Accounting Machine and related punched card equipment was still in operation at a filter manufacturing company in Conroe, Texas. The punched card system was still in use as of 2013.
- 2011: The owner of Cardamation, Robert G. Swartz, dies, and the company, perhaps the last supplier of punch cards and equipment, ceases operation.
Punched cards 
The basic unit of data storage was the punched card. For the IBM 80-column card, introduced in 1928, each column represented a single digit, letter or special character. A data value consisted of a field of adjacent columns. An employee number might occupy 5 columns; hourly pay rate, 3 columns; hours worked in a given week, 2 columns; department number 3 columns; project charge code 6 columns and so on.
IBM Stub cards or Short cards required unit record equipment with interchangeable feeds. For 51-column stub cards such feeds were available for the IBM 077, 080, 082, 402, 403, 419, 514, 519, and 523. Other stub cards could be read only by the IBM 514 and 519.
Original data was usually punched into cards by workers, often women, known as keypunch operators. Their work was often checked by a second operator using a verifier machine. Cards were also produced automatically by various unit record machines and later by computer output devices.
An activity in many unit record shops was sorting card decks into the order necessary for the next processing step. Sorters, like the IBM 80 series Card Sorters, sorted input cards into one of 13 pockets depending on the holes punched in a selected column and the sorter's settings. The 13th pocket was for blanks and rejects. Sorting an input card deck into ascending sequence on a multiple column field, such as an employee number, was done by a radix sort, bucket sort, or a combination of the two methods.
Reports and summary data were generated by accounting or tabulating machines. The original tabulators only counted the presence of a hole at a location on a card. Simple logic, like and's and or's could be done using relays.
Later tabulators, such as the IBM 407, directed by a control panel, could do both addition and subtraction of selected fields to one or more counters and print each card on its own line. At some signal, say a following card with a different customer number, totals could be printed for the just completed customer number.
In 1931, IBM introduced the model 600 multiplying punch. The ability to divide became commercially available after World War II. The earliest of these calculating punches were electro-mechanical. Later models employed vacuum tube logic. Electronic modules developed for these units were used in early computers, such as the IBM 650. The Bull Gamma 3 calculator could be attached to tabulating machines, unlike the stand-alone IBM calculators.
Card punching 
Card punching operations included:
- Gang punching - producing a large number of identically punched cards—for example, for inventory tickets.
- Reproducing - reproducing a card deck in its entirety or just selected fields. A payroll master card deck might be reproduced at the end of a pay period with the hours worked and net pay fields blank and ready for the next pay period's data. Computer programmers who created their programs in the form of card decks reproduced them to make backups.
- Summary punching - punching new cards with details and totals from an attached tabulating machine.
- Mark sense reading - detecting electrographic lead pencil marks on ovals printed on the card and punching the corresponding data values into the card.
Singularly or in combination, these operations were provided in a variety of machines. Document origination machines, such as the IBM 519, could perform all of the above operations.
The IBM 549 Ticket Converter read data from Kimball tags, copying that data to punched cards.
A collator had two input hoppers and four output pockets. These machines could merge or match card decks based on the control panel's wiring as illustrated here. Collators performed operations comparable to a database join.
An interpreter would print characters equivalent to the values of columns on the card. The columns to be printed could be selected and even reordered, based on the machine's control panel wiring. Later models could print on one of several rows on the card. Unlike keypunches, which printed values directly above each column, interpreters generally used a font that was a little wider than a column and could only print up to 60 characters per row. Typical later models include the IBM 550 Numeric Interpreter and the IBM 557 Alphabetic Interpreter.
Transmission of punched card data 
Electrical transmission of punched card data was invented in the early 1930s. The device was called an Electrical Remote Control of Office Machines and was assigned to IBM. Inventors were Joseph C. Bolt of Boston & Curt I. Johnson; Worcester, Mass. assors to the Tabulating Machine Co., Endicott, NY. The Distance Control Device received a US patent in Aug.9,1932: U.S. Patent 1,870,230. Letters from IBM talk about filling in Canada in 9/15/1931.
Processing punched tape 
The IBM 046 Tape-to-Card Punch and the IBM 047 Tape-to-Card Printing Punch (which was almost identical, but with the addition of a printing mechanism) read data from punched paper tape and punched that data into cards. The IBM 063 Card-Controlled Tape Punch read punched cards, punching that data into paper tape.
Control panel wiring 
The operation of tabulators and many other types of unit record equipment was directed by a control panel. The panels had a rectangular array of holes called hubs which were organized into groups. Wires with metal ferrules at each end were placed in the hubs to make connections. The output from some card column positions might connected to a tabulating machine's counter, for example. A shop would typically have separate control panels for each task a machine was used for.
Note: Control panel wiring is sometimes referred to as programming, however that term applies only to the control panels of calculators, such as the IBM 602 and IBM 604, that specified a sequence of operations.
Paper handling equipment 
For many applications, the volume of fan-fold paper produced by tabulators required other machines, not considered to be unit record machines, to ease paper handling.
- A decollator separated multi-part fan-fold paper into individual stacks of one-part fan-fold and removed the carbon paper.
- A burster separated one-part fan-fold paper into individual sheets. For some uses it was desirable to remove the tractor-feed holes on either side of the fan-fold paper. In these cases the form's edge strips were perforated and the burster removed them as well.
See also 
- British Tabulating Machine Company
- Fredrik Rosing Bull
- Gustav Tauschek
- IBM Electromatic Table Printing Machine
- IBM 632 Accounting Machine
- IBM 6400 Series
- Leslie Comrie
- List of IBM products
- Powers Accounting Machine Company
- Remington Rand
- Wallace John Eckert
Notes and references 
- In the late 1800s, early 1900s unit record was a reference to the recording of all information about a transaction or object on one document. At that time the library index card was pointed out as an early example of a unit record. Even unit record desks were manufactured, a desk that included what later, for punched cards, would be called a tub file. This quote We had records of every car and locomotive on the railroad on a key-punched card or other unit record, either generated in the Car Accountant's Office or through other means, from Report of the Railway Accounting Officers 77. Association of American Railroads: Accounting Division. 1888. p. 107. shows that in 1888 1) users were applying the term unit record to punched cards and 2) the term's use was more general than just punched cards. Markus Krajewski in Paper Machines: About Cards & Catalogs, 1548-1929, 2011, MIT, credits Conrad Gessner with developing the unit record concept.
- IBM (1957). Machine Functions. 224-8208-3.
- IBM (1959). Flow Charting and Block Diagramming Techniques. /C20-8008-0.
- Phelps, B.E. "Early Computers at IBM", Annals of the History of Computing v.2.3, July 1980
- Columbia University Computing History - Herman Hollerith
- U.S. Census Bureau: The Hollerith Machine
- U.S. Census Bureau: Tabulation and Processing
- Truesdell, Leon E. (1965). The Development of Punch Card Tabulation in the Bureau of the Census 1890-1940. US GPO.
- "IBM Archives: Hollerith Automatic Horizontal Sorter".
- Computing at Columbia: Timeline - Early
- Durand, Hon. E. Dana (September 23–28, 1912). Tabulation by Mechanical Means - Their Advantages and Limitations, volume VI. Transactions of the Fifteenth International Congress on Hygiene and Demography.
- Cortada, James W. (1993). Before the Computer: IBM, NCR, Burroughs, & Remington Rand & The Industry they Created 1865—1956. Princeton. pp. 56–59.
- IBM Archives: Endicott chronology, 1951-1959
- Information Technology Industry TimeLine
- Cortada p.57
- Pugh p.259
- Van Ness, Robert G. (1962). Principles of Punched Card Data Processing. The Business Press. p. 15.
- Punched Hole Accounting. IBM. 1924. p. 18.
- Engelbourg p.173
- "IBM Archives: 1920". IBM.
- Rojas, Raul (editor) (2001). Encyclopedia of Computers and Computer History. Fitzroy Dearborn. p. 656.
- IBM Type 80 Electric Punched Card Sorting Machine
- IBM 301 Accounting Machine (the Type IV)
- Columbia University Professor Ben Wood
- Pugh, Emerson W. (1995). Building IBM: Shaping an Industry and Its Technology. MIT. p. 67. ISBN 0-262-16147-8.
- Pugh (1995) p.50
- H.W.Egli - BULL Tabulator model T30
- Bashe, Charles J.; Johnson, Lyle R; Palmer, John H.; Pugh, Emerson W. (1986). IBM's Early Computers. MIT. p. 14. ISBN 0-262-02225-7.
- Eames, Charles; Eames, Ray (1973). A Computer Perspective. Cambridge, Mass: Harvard University Press. p. 95. The date given, 1920, should be 1931 (see the Columbia Difference Tabulator web site)
- Columbia Difference Tabulator
- Columbia Alumni News, Vol.XXIII, No.11, December 11, 1931, p.1
- IBM 077 Collator
- IBM Archive: Endicott card manufacturing
- Phelps, B.E. (July 1980). "Early Computers at IBM". Annals of the History of Computing (IEEE Computer Society) 2 (3): 254.
- Equipements à cartes perforées (Punched cards machines) type A (GR) 1941-1950
- Bashe (1986) p.21
- The IBM 602 Calculating Punch
- IBM 603 Electronic Multiplier
- Bashe (1986) p.62
- IBM Archives: Endicott chronology 1941-1949
- Bull Gamma 3 1952-1960
- Bull Gamma 3
- Bashe, Charles J.; Pugh, Emerson W.; Johnson, Lyle R.; Palmer, John H. (1986). IBM's Early Computers. MIT Press. pp. 461–474. ISBN 0-262-02225-7.
- Computer History Museum: Underwood Corporation
- An Underwood-Samas sorter
- IBM Archives - DPD chronology
- IBM 1940 products brochure
- Bashe (1986) pp.465–494 Chapter 12 Broadening the Base, a history of IBM's 1401 and 1403 development.
- Columbia University: The IBM 609 Calculator
- IBM System 3
- IBM 407 Accounting Machine
- IBM Rochester chronology, page3
- IBM Rochester chronology
- IBM 029 Card Punch
- Visit to a working IBM 402 in Conroe, Texas
- Conroe company still using computers museums want to put on display By Craig Hlavaty, Houston Chronicle, April 24, 2013
- IBM (1956). The Design of IBM Cards. p. 22. 22-5526-4.
- IBM (1949). The How and Why of IBM Mark Sensing. 52-5862-0.
- IBM Card Interpreters
- IBM (1958). IBM 063 Card-Controlled Tape Punch. 224-5997-3.
- IBM (1963). IBM Accounting Machine: 402, 403 and 419 Principles of Operation. 224-1614-13.
- IBM (1956). IBM Reference Manual: Functional Wiring Principles. 22-6275-0.
Further reading 
Note: Most IBM form numbers end with an edition number, a hyphen followed by one or two digits.
- Aspray (ed.), William (1990). Computing before Computers. Iowa State University Press. p. 266. ISBN 0-8138-0047-1.
- Brennan, Jean Ford (1971). The IBM Watson Laboratory at Columbia University: A History. IBM. p. 68.
- Cortada, James W. (1983). An Annotated Bibliography on the History of Data Processing. Greenwood. p. 215. ISBN 0-313-24001-9.
- Cortada, James W. (1993). Before the Computer: IBM, NCR, Burroughs, & Remington Rand & the Industry they created, 1865 - 1956. Princeton. p. 344. ISBN 0-691-04807-X.
- Engelbourg, Saul (1954). International Business Machines: A Business History (Ph.D.). Columbia University. pp. 385. Reprinted by Arno Press, 1976, from the best available copy. Some text is illegible.
- Krawitz, Miss Eleanor (November 1949). "Watson Scientific Computing Laboratory: A Center for Scientific Research Using Calculating Machines". Columbia Engineering Quarterly.
- Lars, Heide (2009). Punched-Card Systems and the Early Information Explosion, 1880--1945. John Hopkins U Press. p. 369. ISBN 0-8018-9143-4.
- Pugh, Emerson W.; Heide, Lars. IEEE STARS: Early Punched Card Equipment, 1880-1951. IEEE.
- Randell, Brian (1982). The Origins of Digital Computers: Selected Papers (3 ed.). Springer-Verlag. p. 580. ISBN 0-387-11319-3. includes Hollerith (1889) reprint
- Hollerith, Hollerith's early machines
- Austrian, Geoffrey D. (1982). Herman Hollerith: The Forgotten Giant of Information Processing. Columbia University Press. p. 418. ISBN 0-231-05146-8.
- Hollerith, Herman (April 1889). "An Electric Tabulating System". The Quarterly, Columbia University School of Mines X (16): 238–255. From the Columbia Univ. History site: This article is the basis for his 1890 Columbia Ph.D. Extracts reprinted in (Randell, 1982).
- Hollerith, Herman (1890). In connection with the electric tabulation system which has been adopted by U.S. government for the work of the census bureau. Ph.D. dissertation. Columbia University School of Mines.
- Hollerith, Herman (December 1894). "The Electrical Tabulating Machine". Journal of the Royal Statistical Society (Blackwell Publishing) 57 (4): 678–682. doi:10.2307/2979610. JSTOR 2979610. From (Randell, 1982) ... brief... fascinating article... describes the way in which tabulators and sorters were used on ... 100 million cards ... 1890 census.
- Truedsell, Leon E. (1965). The Development of Punch Card Tabulation in the Bureau of the Census 1890-1940. US GPO. Includes extensive, detailed, description of Hollerith's first machines and their use for the 1890 census.
- Punched card applications
- Baehne (editor), G.W. (1935). Practical Applications of the Punched Card Method in Colleges and Universities. Columbia University. p. 442. – With 42 contributors and articles ranging from Analysis of College Test Results to Uses of the Automatic Multiplying Punch this is book provides an extensive view of unit record equipment use over a wide range of applications. For details of this book see The Baehne Book..
- Ferris, Lorna; et al. (1948). Bibliography on the Uses of Punched Cards. MIT.
- Grosch, Herb (1945). Bibliography on the Use of IBM Machines in Scientific Research, Statistics, and Education. IBM. (source: Frank da Cruz (Feb 6, 2010). "Herb Grosch". Columbia University. Retrieved 14 June 2011.) There is a 1954 edition, Ann F. Beach, et al., similar title and a 1956 edition, Joyce Alsop.
- IBM (1944). IBM Accounting Course. 25-4933-3-3M-ME-1-49. Describes several punched card applications.
- Eckert, W.J. (1940). Punched Card Methods in Scientific Computation. Columbia University. p. 136. ISBN 0-262-05030-7. Note: ISBN is for a reprint ed.
- The machines
- Bureau of Naval Personnel (1971). Basic Data Processing. Dover. p. 315. ISBN 0-486-20229-1. Unabridged edition of "Data Processing Tech 3 &2", aka. "Rate Training manual NAVPERS 10264-B", 3rd revised ed. 1970
- Brooks, Jr., Frederick P.; Iverson, Kenneth E. (1963). Automatic Data Processing. Wiley. p. 494. Descriptions of the various machines include examples of control panel wiring.
- Fierheller, George A. (2006). Do not fold, spindle or mutilate: the 'hole' story of punched cards. Stewart Pub. ISBN 1-894183-86-X. Retrieved March 30, 2011. An accessible book of recollections (sometimes with errors), with photographs and descriptions of many unit record machines.
- Friedman, Burton Dean (1955). Punched Card Primer. American Book - Stratford Press. This elementary introduction to punched card systems is unusual because unlike most others, it not only deals with the IBM systems but also illustrates the card formats and equipment offered by Remington Rand and Underwood Samas. Erwin Tomash Library
- IBM (1940). IBM products brochure.
- IBM. An Introduction to IBM Punched Card Data Processing. F20-0074.
- IBM (1955-56). IBM Sales Manual (unit record equipment pages only).
- IBM (1957). Machine Functions. 224-8208-3. A simplified description of common IBM machines and their uses.
- IBM (1957). IBM Equipment Summary. With descriptions, photos and rental prices.
- IBM (1959). IBM Operators Guide: Reference Manual. A24-1010-0. The IBM Operators Guide, 22-8485 was an earlier edition of this book
- Murray, Francis J. (1961). Mathematical Machines Volume 1: Digital Computers. Columbia University Press. Has extensive descriptions of unit record machine construction.
- Columbia University Computing History IBM Tabulators and Accounting Machines IBM Calculators IBM Card Interpreters IBM Reproducing and Summary Punches IBM Collators
- Columbia University Computing History: L.J. Comrie From that site Comrie was the first to turn punched-card equipment to scientific use
- History of Bull Extracted and translated from Science et Vie Micro magazine, No. 74, July–August, 1990: The very international history of a French giant
- Musée virtuel de Bull et de l'informatique Française: Information Technology Industry TimeLine From that site The present TimeLine page differs from similar pages available on the Internet because it is focused more on the industry than on "inventions". It was originally designed to show the place of the European and more specifically the French computer industry facing its world-wide competition. Most of published time-line charts either consider that everything had an American origin or they show their country patriotism (French, Italian, Russian or British) or their company patriotism.
- Musée virtuel de Bull et de l'informatique Française (Virtual Museum of French computers) Systems Catalog
- Early office museum
- IBM Archives
- IBM Punch Card Systems in the U.S. Army
- IBM early Card Reader and 1949 electronic Calculator video of unit record equipment in museum
- Working Tabulating machines and punched card equipment in technikum29 Computermuseum (nr. Frankfurt/Main, Germany)