ENIAC

ENIAC (

ENIAC was designed by John Mauchly and J. Presper Eckert to calculate artillery firing tables for the United States Army's Ballistic Research Laboratory (which later became a part of the Army Research Laboratory).^[7][8] However, its first program was a study of the feasibility of the thermonuclear weapon.^[9][10]

ENIAC was completed in 1945 and first put to work for practical purposes on December 10, 1945.^[11]

ENIAC was formally dedicated at the

ENIAC was formally accepted by the U.S. Army Ordnance Corps in July 1946. It was transferred to Aberdeen Proving Ground in Aberdeen, Maryland in 1947, where it was in continuous operation until 1955.

Development and design

ENIAC's design and construction was financed by the United States Army, Ordnance Corps, Research and Development Command, led by Major General

ENIAC was a large, modular computer, composed of individual panels to perform different functions. Twenty of these modules were accumulators that could not only add and subtract, but hold a ten-digit decimal number in memory. Numbers were passed between these units across several general-purpose buses (or trays, as they were called). In order to achieve its high speed, the panels had to send and receive numbers, compute, save the answer and trigger the next operation, all without any moving parts. Key to its versatility was the ability to branch; it could trigger different operations, depending on the sign of a computed result.

Components

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By the end of its operation in 1956, ENIAC contained 18,000

ENIAC used ten-position ring counters to store digits; each digit required 36 vacuum tubes, 10 of which were the dual triodes making up the flip-flops of the ring counter. Arithmetic was performed by "counting" pulses with the ring counters and generating carry pulses if the counter "wrapped around", the idea being to electronically emulate the operation of the digit wheels of a mechanical adding machine.^[24]

ENIAC had 20 ten-digit signed

It was possible to wire the carry of one accumulator into another accumulator to perform arithmetic with double the precision, but the accumulator carry circuit timing prevented the wiring of three or more for even higher precision. ENIAC used four of the accumulators (controlled by a special multiplier unit) to perform up to 385 multiplication operations per second; five of the accumulators were controlled by a special divider/square-rooter unit to perform up to 40 division operations per second or three square root operations per second.

The other nine units in ENIAC were the initiating unit (started and stopped the machine), the cycling unit (used for synchronizing the other units), the master programmer (controlled loop sequencing), the reader (controlled an IBM punch-card reader), the printer (controlled an IBM card punch), the constant transmitter, and three function tables.^[28][29]

Operation times

The references by Rojas and Hashagen (or Wilkes)^[17] give more details about the times for operations, which differ somewhat from those stated above.

The basic machine cycle was 200 microseconds (20 cycles of the 100 kHz clock in the cycling unit), or 5,000 cycles per second for operations on the 10-digit numbers. In one of these cycles, ENIAC could write a number to a register, read a number from a register, or add/subtract two numbers.

A multiplication of a 10-digit number by a d-digit number (for d up to 10) took d+4 cycles, so the multiplication of a 10-digit number by 10-digit number took 14 cycles, or 2,800 microseconds—a rate of 357 per second. If one of the numbers had fewer than 10 digits, the operation was faster.

Division and square roots took 13(d+1) cycles, where d is the number of digits in the result (quotient or square root). So a division or square root took up to 143 cycles, or 28,600 microseconds—a rate of 35 per second. (Wilkes 1956:20^[17] states that a division with a 10-digit quotient required 6 milliseconds.) If the result had fewer than ten digits, it was obtained faster.

ENIAC is able to process about 500 FLOPS,^[30] compared to modern supercomputers' petascale and exascale computing power.

Reliability

ENIAC used common

Several tubes burned out almost every day, leaving ENIAC nonfunctional about half the time. Special high-reliability tubes were not available until 1948. Most of these failures, however, occurred during the warm-up and cool-down periods, when the tube heaters and cathodes were under the most thermal stress. Engineers reduced ENIAC's tube failures to the more acceptable rate of one tube every two days. According to an interview in 1989 with Eckert, "We had a tube fail about every two days and we could locate the problem within 15 minutes."[32] In 1954, the longest continuous period of operation without a failure was 116 hours—close to five days.

Programming

ENIAC could be programmed to perform complex sequences of operations, including loops, branches, and subroutines. However, instead of the stored-program computers that exist today, ENIAC was just a large collection of arithmetic machines, which originally had programs set up into the machine^[33] by a combination of plugboard wiring and three portable function tables (containing 1,200 ten-way switches each).^[34] The task of taking a problem and mapping it onto the machine was complex, and usually took weeks. Due to the complexity of mapping programs onto the machine, programs were only changed after huge numbers of tests of the current program.^[35] After the program was figured out on paper, the process of getting the program into ENIAC by manipulating its switches and cables could take days. This was followed by a period of verification and debugging, aided by the ability to execute the program step by step. A programming tutorial for the modulo function using an ENIAC simulator gives an impression of what a program on the ENIAC looked like.^[36][37][38]

ENIAC's six primary programmers, Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman, not only determined how to input ENIAC programs, but also developed an understanding of ENIAC's inner workings.^[39][40] The programmers were often able to narrow bugs down to an individual failed tube which could be pointed to for replacement by a technician.^[41]

Programmers

The ENIAC Programmers (As Told By U.S. Chief Technology Officer Megan Smith)

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Problems playing this file? See media help.

During

These women were not, as computer scientist and historian Kathryn Kleiman was once told, "refrigerator ladies", i.e., models posing in front of the machine for press photography.^[43] However, some of the women did not receive recognition for their work on the ENIAC in their entire lifetimes.^[19] After the war ended, the women continued to work on the ENIAC. Their expertise made their positions difficult to replace with returning soldiers.^[44]

These early programmers were drawn from a group of about two hundred women employed as

Herman Goldstine selected the programmers, whom he called operators, from the computers who had been calculating ballistics tables with mechanical desk calculators, and a differential analyzer prior to and during the development of ENIAC.^[19] Under Herman and Adele Goldstine's direction, the computers studied ENIAC's blueprints and physical structure to determine how to manipulate its switches and cables, as programming languages did not yet exist. Though contemporaries considered programming a clerical task and did not publicly recognize the programmers' effect on the successful operation and announcement of ENIAC,^[19] McNulty, Jennings, Snyder, Wescoff, Bilas, and Lichterman have since been recognized for their contributions to computing.^[48][49][50] Three of the current (2020) Army supercomputers Jean, Kay, and Betty are named after Jean Bartik (Betty Jennings), Kay McNulty, and Betty Snyder respectively.^[51]

The "programmer" and "operator" job titles were not originally considered professions suitable for women. The labor shortage created by World War II helped enable the entry of women into the field.^[19] However, the field was not viewed as prestigious, and bringing in women was viewed as a way to free men up for more skilled labor. Essentially, women were seen as meeting a need in a temporary crisis.^[19] For example, the National Advisory Committee for Aeronautics said in 1942, "It is felt that enough greater return is obtained by freeing the engineers from calculating detail to overcome any increased expenses in the computers' salaries. The engineers admit themselves that the girl computers do the work more rapidly and accurately than they would. This is due in large measure to the feeling among the engineers that their college and industrial experience is being wasted and thwarted by mere repetitive calculation".^[19]

Following the initial six programmers, an expanded team of a hundred scientists was recruited to continue work on the ENIAC. Among these were several women, including

Related to ENIAC's role in the hydrogen bomb was its role in the

A press conference was held on February 1, 1946,[19] and the completed machine was announced to the public the evening of February 14, 1946,^[61] featuring demonstrations of its capabilities. Elizabeth Snyder and Betty Jean Jennings were responsible for developing the demonstration trajectory program, although Herman and Adele Goldstine took credit for it.^[19] The machine was formally dedicated the next day^[62] at the University of Pennsylvania. None of the women involved in programming the machine or creating the demonstration were invited to the formal dedication nor to the celebratory dinner held afterwards.^[63]

The original contract amount was $61,700; the final cost was almost $500,000 (approximately equivalent to $9,000,000 in 2023). It was formally accepted by the U.S. Army Ordnance Corps in July 1946. ENIAC was shut down on November 9, 1946, for a refurbishment and a memory upgrade, and was transferred to Aberdeen Proving Ground, Maryland in 1947. There, on July 29, 1947, it was turned on and was in continuous operation until 11:45 p.m. on October 2, 1955, when it was retired in favor of the more efficient EDVAC and ORDVAC computers.^[2]

Role in the development of the EDVAC

A few months after ENIAC's unveiling in the summer of 1946, as part of "an extraordinary effort to jump-start research in the field",^[64] the Pentagon invited "the top people in electronics and mathematics from the United States and Great Britain"^[64] to a series of forty-eight lectures given in Philadelphia, Pennsylvania; all together called The Theory and Techniques for Design of Digital Computers—more often named the Moore School Lectures.^[64] Half of these lectures were given by the inventors of ENIAC.^[65]

ENIAC was a one-of-a-kind design and was never repeated. The freeze on design in 1943 meant that it lacked some innovations that soon became well-developed, notably the ability to store a program. Eckert and Mauchly started work on a new design, to be later called the

A number of improvements were made to ENIAC after 1947, including a primitive read-only stored programming mechanism using the function tables as program ROM,^{[66][67][68][69][70][71]} after which programming was done by setting the switches.^[72] The idea has been worked out in several variants by Richard Clippinger and his group, on the one hand, and the Goldstines, on the other,^[73] and it was included in the ENIAC patent.^[74] Clippinger consulted with von Neumann on what instruction set to implement.^[66][75][76] Clippinger had thought of a three-address architecture while von Neumann proposed a one-address architecture because it was simpler to implement. Three digits of one accumulator (#6) were used as the program counter, another accumulator (#15) was used as the main accumulator, a third accumulator (#8) was used as the address pointer for reading data from the function tables, and most of the other accumulators (1–5, 7, 9–14, 17–19) were used for data memory.

In March 1948 the converter unit was installed,^[77] which made possible programming through the reader from standard IBM cards.^[78][79] The "first production run" of the new coding techniques on the Monte Carlo problem followed in April.^[77][80] After ENIAC's move to Aberdeen, a register panel for memory was also constructed, but it did not work. A small master control unit to turn the machine on and off was also added.^[81]

The programming of the stored program for ENIAC was done by Betty Jennings, Clippinger, Adele Goldstine and others.^{[82][83][67][66]} It was first demonstrated as a stored-program computer in April 1948,^[84] running a program by Adele Goldstine for John von Neumann. This modification reduced the speed of ENIAC by a factor of 6 and eliminated the ability of parallel computation, but as it also reduced the reprogramming time^[76][66] to hours instead of days, it was considered well worth the loss of performance. Also analysis had shown that due to differences between the electronic speed of computation and the electromechanical speed of input/output, almost any real-world problem was completely I/O bound, even without making use of the original machine's parallelism. Most computations would still be I/O bound, even after the speed reduction imposed by this modification.

Early in 1952, a high-speed shifter was added, which improved the speed for shifting by a factor of five. In July 1953, a 100-word expansion core memory was added to the system, using binary-coded decimal, excess-3 number representation. To support this expansion memory, ENIAC was equipped with a new Function Table selector, a memory address selector, pulse-shaping circuits, and three new orders were added to the programming mechanism.^[66]

Comparison with other early computers

Mechanical computing machines have been around since Archimedes' time (see: Antikythera mechanism), but the 1930s and 1940s are considered the beginning of the modern computer era.

ENIAC was, like the IBM

Like the Colossus, ENIAC required rewiring to reprogram until April 1948.[85] In June 1948, the Manchester Baby ran its first program and earned the distinction of first electronic stored-program computer.^[86][87][88] Though the idea of a stored-program computer with combined memory for program and data was conceived during the development of ENIAC, it was not initially implemented in ENIAC because World War II priorities required the machine to be completed quickly, and ENIAC's 20 storage locations would be too small to hold data and programs.

Public knowledge

The Z3 and Colossus were developed independently of each other, and of the ABC and ENIAC during World War II. Work on the ABC at

The main parts were 40 panels and three portable function tables (named A, B, and C). The layout of the panels was (clockwise, starting with the left wall):

Left wall

• Initiating Unit
• Cycling Unit
• Master Programmer – panel 1 and 2
• Function Table 1 – panel 1 and 2
• Accumulator 1
• Accumulator 2
• Divider and Square Rooter
• Accumulator 3
• Accumulator 4
• Accumulator 5
• Accumulator 6
• Accumulator 7
• Accumulator 8
• Accumulator 9

Back wall

• Accumulator 10
• High-speed Multiplier – panel 1, 2, and 3
• Accumulator 11
• Accumulator 12
• Accumulator 13
• Accumulator 14

Right wall

• Accumulator 15
• Accumulator 16
• Accumulator 17
• Accumulator 18
• Function Table 2 – panel 1 and 2
• Function Table 3 – panel 1 and 2
• Accumulator 19
• Accumulator 20
• Constant Transmitter – panel 1, 2, and 3
• Printer – panel 1, 2, and 3

An IBM card reader was attached to Constant Transmitter panel 3 and an IBM card punch was attached to Printer Panel 2. The Portable Function Tables could be connected to Function Table 1, 2, and 3.^[93]

Parts on display

Pieces of ENIAC are held by the following institutions:

• The School of Engineering and Applied Science at the University of Pennsylvania has four of the original forty panels (Accumulator #18, Constant Transmitter Panel 2, Master Programmer Panel 2, and the Cycling Unit) and one of the three function tables (Function Table B) of ENIAC (on loan from the Smithsonian).^[93]
• The Smithsonian has five panels (Accumulators 2, 19, and 20; Constant Transmitter panels 1 and 3; Divider and Square Rooter; Function Table 2 panel 1; Function Table 3 panel 2; High-speed Multiplier panels 1 and 2; Printer panel 1; Initiating Unit)^[93] in the National Museum of American History in Washington, D.C.^[19] (but apparently not currently on display).
• The Science Museum in London has a receiver unit on display.
• The Computer History Museum in Mountain View, California has three panels (Accumulator #12, Function Table 2 panel 2, and Printer Panel 3) and portable function table C on display (on loan from the Smithsonian Institution).^[93]
• The University of Michigan in Ann Arbor has four panels (two accumulators, High-speed Multiplier panel 3, and Master Programmer panel 2),^[93] salvaged by Arthur Burks.
• The
  United States Army Ordnance Museum at Aberdeen Proving Ground, Maryland
  , where ENIAC was used, has Portable Function Table A.
• The U.S. Army Field Artillery Museum in Fort Sill, as of October 2014, obtained seven panels of ENIAC that were previously housed by The Perot Group in Plano, Texas.^[94] There are accumulators #7, #8, #11, and #17;^[95] panel #1 and #2 that connected to function table #1,^[93] and the back of a panel showing its tubes. A module of tubes is also on display.
• The United States Military Academy at West Point, New York, has one of the data entry terminals from the ENIAC.
• The Heinz Nixdorf Museum in Paderborn, Germany, has three panels (Printer panel 2 and High-speed Function Table)^[93] (on loan from the Smithsonian Institution). In 2014 the museum decided to rebuild one of the accumulator panels – reconstructed part has the look and feel of a simplified counterpart from the original machine.^[96][97]

Recognition

ENIAC was named an

In 1996, in honor of the ENIAC's 50th anniversary, The University of Pennsylvania sponsored a project named "ENIAC-on-a-Chip", where a very small silicon computer chip measuring 7.44 mm by 5.29 mm was built with the same functionality as ENIAC. Although this 20 MHz chip was many times faster than ENIAC, it had but a fraction of the speed of its contemporary microprocessors in the late 1990s.^{[99][100][101]}

In 1997, the six women who did most of the programming of ENIAC were inducted into the

In 2011, in honor of the 65th anniversary of the ENIAC's unveiling, the city of Philadelphia declared February 15 as ENIAC Day.[105]^[106][107]

The ENIAC celebrated its 70th anniversary on February 15, 2016.^[108]

See also

• History of computing
• History of computing hardware
• Women in computing
• List of vacuum-tube computers
• Military computers
• Unisys
• Arthur Burks
• Betty Holberton
• Frances Bilas Spence
• John Mauchly
• J. Presper Eckert
• Jean Jennings Bartik
• Kathleen Antonelli (Kay McNulty)
• Marlyn Meltzer
• Ruth Lichterman Teitelbaum

Notes

References

• doi:10.1109/jrproc.1947.234265
  .
• S2CID 14205498
  .
• Clippinger, R. F. (September 29, 1948). "A Logical Coding System Applied to the ENIAC". Ballistic Research Laboratories Report (673). Archived from the original on January 3, 2010. Retrieved January 27, 2010. (original source)
• ISBN 9780192840554
  .
• De Mol, Liesbeth; Bullynck, Maarten (2008). "A Week-End Off: The First Extensive Number-Theoretical Computation on ENIAC". In Beckmann, Arnold; Dimitracopoulos, Costas; Löwe, Benedikt (eds.). Logic and Theory of Algorithms: 4th Conference on Computability in Europe, CiE 2008 Athens, Greece, June 15-20, 2008, Proceedings. Springer Science & Business Media. pp. 158–167.
  ISBN 9783540694052
  .
• Eckert, J. Presper, The ENIAC (in Nicholas Metropolis, J. Howlett, Gian-Carlo Rota, (editors), A History of Computing in the Twentieth Century, Academic Press, New York, 1980, pp. 525–540)
• Eckert, J. Presper and John Mauchly, 1946, Outline of plans for development of electronic computers, 6 pages. (The founding document in the electronic computer industry.)
• Fritz, W. Barkley, The Women of ENIAC (in IEEE Annals of the History of Computing, Vol. 18, 1996, pp. 13–28)
• Goldstine, Adele (1946). "A Report on the ENIAC". FTP.arl.mil. 1 (1). Chapter 1 -- Introduction: 1.1.2. The Units of the ENIAC. original source
• Goldstine, Herman H.; Goldstine, Adele K. (1946). "The electronic numerical integrator and computer (ENIAC)". Mathematics of Computation. 2 (15): 97–110.
  ISSN 0025-5718
  . (also reprinted in The Origins of Digital Computers: Selected Papers, Springer-Verlag, New York, 1982, pp. 359–373)
• Goldstine, Adele K. (July 10, 1947). Central Control for ENIAC. p. 1. Unlike the later 60- and 100-order codes this one [51 order code] required no additions to ENIAC's original hardware. It would have worked more slowly and offered a more restricted range of instructions but the basic structure of accumulators and instructions changed only slightly.
• ISBN 9780691023670
  .
• Haigh, Thomas; Priestley, Mark; Rope, Crispin (April–June 2014b). "Engineering 'The Miracle of the ENIAC': Implementing the Modern Code Paradigm". IEEE Annals of the History of Computing. 36 (2): 41–59.
  S2CID 24359462
  . Retrieved November 13, 2018.
• Haigh, Thomas; Priestley, Mark; Rope, Crispin (2016). ENIAC in Action: Making and Remaking the Modern Computer.
  ISBN 978-0-262-53517-5
  .
• Light, Jennifer S. (1999). "When Computers Were Women" (PDF). Technology and Culture. 40 (3): 455–483.
  S2CID 108407884. Archived from the original
  (PDF) on November 22, 2015. Retrieved March 9, 2015.
• Los Alamos Scientific Laboratory
  , 10–15 June 1976.")
• McCartney, Scott (1999). ENIAC: The Triumphs and Tragedies of the World's First Computer. Walker & Co.
  ISBN 978-0-8027-1348-3
  .
• ISBN 978-0-684-80400-2
  .
• Rojas, Raúl; Hashagen, Ulf, editors. The First Computers: History and Architectures, 2000,
  ISBN 0-262-18197-5
• Stuart, Brian L. (2018). "Simulating the ENIAC [Scanning Our Past]". Proceedings of the IEEE. 106 (4): 761–772.
  doi:10.1109/JPROC.2018.2813678
  .
• Stuart, Brian L. (2018). "Programming the ENIAC [Scanning Our Past]". Proceedings of the IEEE. 106 (9): 1760–1770.
  doi:10.1109/JPROC.2018.2843998
  .
• Stuart, Brian L. (2018). "Debugging the ENIAC [Scanning Our Past]". Proceedings of the IEEE. 106 (12): 2331–2345.
  doi:10.1109/JPROC.2018.2878986
  .

Further reading

• Berkeley, Edmund. GIANT BRAINS or machines that think. John Wiley & Sons, inc., 1949. Chapter 7 Speed – 5000 Additions a Second: Moore School's ENIAC (Electronic Numerical Integrator And Computer)
• ISBN 978-0-375-42277-5
  .
• Gumbrecht, Jamie (February 8, 2011). "Rediscovering WWII's 'computers'". CNN.com. Retrieved February 9, 2011.
• Hally, Mike. Electronic Brains: Stories from the Dawn of the Computer Age,
  ISBN 0-309-09630-8
• LCCN 79-90567
  .
• Tompkins, C. B.; Wakelin, J. H.; High-Speed Computing Devices,
  McGraw-Hill
  , 1950.
• Stern, Nancy (1981). From ENIAC to UNIVAC: An Appraisal of the Eckert–Mauchly Computers.
  ISBN 978-0-932376-14-5
  .
• "ENIAC Operating Manual" (PDF). www.bitsavers.org.

External links

Wikimedia Commons has media related to ENIAC.

• ENIAC simulation
• Another ENIAC simulation
• Pulse-level ENIAC simulator
• 3D printable model of the ENIAC
• Q&A: A lost interview with ENIAC co-inventor J. Presper Eckert
• Interview with Eckert Transcript of a video interview with Eckert by David Allison for the National Museum of American History, Smithsonian Institution on February 2, 1988. An in-depth, technical discussion on ENIAC, including the thought process behind the design.
• Oral history interview with J. Presper Eckert,
  Charles Babbage Institute, University of Minnesota. Eckert, a co-inventor of ENIAC, discusses its development at the University of Pennsylvania's Moore School of Electrical Engineering; describes difficulties in securing patent rights for ENIAC and the problems posed by the circulation of John von Neumann's 1945 First Draft of the Report on EDVAC
  , which placed the ENIAC inventions in the public domain. Interview by Nancy Stern, 28 October 1977.
• Oral history interview with Carl Chambers,
  Charles Babbage Institute
  , University of Minnesota. Chambers discusses the initiation and progress of the ENIAC project at the University of Pennsylvania Moore School of Electrical Engineering (1941–46). Oral history interview by Nancy B. Stern, 30 November 1977.
• Oral history interview with Irven A. Travis,
  Charles Babbage Institute
  , University of Minnesota. Travis describes the ENIAC project at the University of Pennsylvania (1941–46), the technical and leadership abilities of chief engineer Eckert, the working relations between John Mauchly and Eckert, the disputes over patent rights, and their resignation from the university. Oral history interview by Nancy B. Stern, 21 October 1977.
• Oral history interview with S. Reid Warren,
  Charles Babbage Institute
  , University of Minnesota. Warren served as supervisor of the EDVAC project; central to his discussion are J. Presper Eckert and John Mauchly and their disagreements with administrators over patent rights; discusses John von Neumann's 1945 draft report on the EDVAC, and its lack of proper acknowledgment of all the EDVAC contributors.
• ENIAC Programmers Project
• The women of ENIAC
• Programming ENIAC
• How ENIAC took a Square Root
• Mike Muuss: Collected ENIAC documents
• ENIAC chapter in Karl Kempf, Electronic Computers Within The Ordnance Corps, November 1961
• The ENIAC Story, Martin H. Weik, Ordnance Ballistic Research Laboratories, 1961
• ENIAC museum at the University of Pennsylvania
• ENIAC specifications from Ballistic Research Laboratories Report No. 971 December 1955, (A Survey of Domestic Electronic Digital Computing Systems)
• A Computer Is Born, Michael Kanellos, 60th anniversary news story, CNet, February 13, 2006
• 1946 film restored, Computer History Archives Project