
ENIAC (; Electronic Numerical Integrator and Computer)
was the first
programmable,
electronic, general-purpose
digital computer, completed in 1945.
Other computers had some of these features, but ENIAC was the first to have them all. It was
Turing-complete and able to solve "a large class of numerical problems" through reprogramming.
ENIAC was designed by
John Mauchly
John William Mauchly ( ; August 30, 1907 – January 8, 1980) was an American physicist who, along with J. Presper Eckert, designed ENIAC, the first general-purpose electronic digital computer, as well as EDVAC, BINAC and UNIVAC I, the f ...
and
J. Presper Eckert to calculate
artillery
Artillery consists of ranged weapons that launch Ammunition, munitions far beyond the range and power of infantry firearms. Early artillery development focused on the ability to breach defensive walls and fortifications during sieges, and l ...
firing tables for the
United States Army
The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...
's
Ballistic Research Laboratory (which later became a part of the
Army Research Laboratory
The U.S. Army Combat Capabilities Development Command Army Research Laboratory (DEVCOM ARL) is the foundational research laboratory for the United States Army under the United States Army Futures Command (AFC). DEVCOM ARL conducts intramural an ...
). However, its first program was a study of the feasibility of the
thermonuclear weapon
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lowe ...
.
ENIAC was completed in 1945 and first put to work for practical purposes on December 10, 1945.
[*]
ENIAC was formally dedicated at the
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
on February 15, 1946, having cost $487,000 (), and called a "Giant Brain" by the press. It had a speed on the order of one thousand times faster than that of
electro-mechanical machines.
ENIAC was formally accepted by the U.S. Army Ordnance Corps in July 1946. It was transferred to
Aberdeen Proving Ground
Aberdeen Proving Ground (APG) is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work at APG. There are 11 major commands among the tenant units, ...
in
Aberdeen, Maryland in 1947, where it was in continuous operation until 1955.
The 1948
Manchester Baby was the first machine to contain all the elements essential to a modern electronic digital computer, as it could be reprogrammed electronically to hold
stored programs instead of requiring setting of switches to program as ENIAC did.
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
Gladeon M. Barnes. The total cost was about $487,000, . The conception of ENIAC began in June 1941, when Friden calculators and
differential analyzers were used by the
United States Army Ordnance Department to compute firing tables for artillery, which was done by graduate students under John Mauchly's supervision. Mauchly began to wonder if electronics could be applied to mathematics for faster calculations. He partnered up with research associate
J. Presper Eckert, as Mauchly wasn't an electronics expert, to draft an electronic computer that could work at an excellent pace. Later, in August 1942, Mauchly proposed an all-electronic calculating machine that could help the U.S. Army calculate complex ballistics tables.
The U.S. Army Ordnance accepted their plan, giving the
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
a six-months research contract for $61,700.
The construction contract was signed on June 5, 1943; work on the computer began in secret at the
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
's
Moore School of Electrical Engineering the following month, under the code name "Project PX", with
John Grist Brainerd as principal investigator.
Herman H. Goldstine persuaded the Army to fund the project, which put him in charge to oversee it for them. Assembly for the computer began in June 1944.
Later, in September of that year, Eckert and Mauchly completed their conception on the computer.
Construction for the computer was complete in May 1945, and testing for it began at the Moore School. Later, in November of that year, the duo, along with
John Brainerd and
Herman Goldstine, issued the first confidential published report on the computer, which talks about how it worked and the methods by which it was programmed.
ENIAC was designed by
Ursinus College physics professor
John Mauchly
John William Mauchly ( ; August 30, 1907 – January 8, 1980) was an American physicist who, along with J. Presper Eckert, designed ENIAC, the first general-purpose electronic digital computer, as well as EDVAC, BINAC and UNIVAC I, the f ...
and
J. Presper Eckert of the University of Pennsylvania.
The team of design engineers assisting the development included Robert F. Shaw (function tables),
Jeffrey Chuan Chu (divider/square-rooter), Thomas Kite Sharpless (master programmer), Frank Mural (master programmer),
Arthur Burks (multiplier),
Harry Huskey (reader/printer) and Jack Davis (accumulators).
Significant development work was undertaken by the female mathematicians who handled the bulk of the ENIAC programming:
Jean Jennings,
Marlyn Wescoff,
Ruth Lichterman,
Betty Snyder,
Frances Bilas, and
Kay McNulty. In 1946, the researchers resigned from the University of Pennsylvania and formed the
Eckert–Mauchly Computer Corporation
The Eckert–Mauchly Computer Corporation (EMCC) (March 1946 – 1950) was a computer company founded by J. Presper Eckert and John Mauchly. It was incorporated on December 22, 1947. After building the ENIAC at the University of Penns ...
.
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
The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers (''decimal fractions'') of th ...
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
By the end of its operation in 1956, ENIAC contained 18,000
vacuum tube
A vacuum tube, electron tube, thermionic valve (British usage), or tube (North America) is a device that controls electric current flow in a high vacuum between electrodes to which an electric voltage, potential difference has been applied. It ...
s, 7,200
crystal diodes, 1,500
relays, 70,000
resistors, 10,000
capacitor
In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...
s, and approximately 5,000,000 hand-
solder
Solder (; North American English, NA: ) is a fusible alloy, fusible metal alloy used to create a permanent bond between metal workpieces. Solder is melted in order to wet the parts of the joint, where it adheres to and connects the pieces aft ...
ed joints. It weighed more than , was roughly tall, deep, and long, occupied and consumed 150 kW of electricity.
Input was possible from an IBM
card reader and an IBM
card punch was used for output. These cards could be used to produce printed output offline using an
IBM
International Business Machines Corporation (using the trademark IBM), nicknamed Big Blue, is an American Multinational corporation, multinational technology company headquartered in Armonk, New York, and present in over 175 countries. It is ...
accounting machine, such as the
IBM 405. While ENIAC had no system to store memory in its inception, these punch cards could be used for external memory storage. In 1953, a 100-
word
A word is a basic element of language that carries semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of what a word is, there is no consensus among linguist ...
magnetic-core memory built by the
Burroughs Corporation
The Burroughs Corporation was a major American manufacturer of business equipment. The company was founded in 1886 as the American Arithmometer Company by William Seward Burroughs I, William Seward Burroughs. The company's history paralleled many ...
was added to ENIAC.
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.
ENIAC had 20 ten-digit signed
accumulators, which used
ten's complement representation and could perform 5,000 simple addition or subtraction operations between any of them and a source (e.g., another accumulator or a constant transmitter) per second. It was possible to connect several accumulators to run simultaneously, so the peak speed of operation was potentially much higher, due to parallel operation.

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
In mathematics, a square root of a number is a number such that y^2 = x; in other words, a number whose ''square'' (the result of multiplying the number by itself, or y \cdot y) is . For example, 4 and −4 are square roots of 16 because 4 ...
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.
Operation times
The references by Rojas and Hashagen (or Wilkes)
give more details about the times for operations, which differ somewhat from those stated above.
The basic machine cycle was 200
microsecond
A microsecond is a unit of time in the International System of Units (SI) equal to one millionth (0.000001 or 10−6 or ) of a second. Its symbol is μs, sometimes simplified to us when Unicode is not available.
A microsecond is to one second, ...
s (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
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 was able to process about 500
FLOPS, compared to
modern supercomputers' petascale and
exascale computing power.
Reliability
ENIAC used common
octal-base radio tubes of the day; the decimal
accumulators were made of
6SN7 flip-flops, while 6L7s, 6SJ7s, 6SA7s and 6AC7s were used in logic functions. Numerous
6L6s and
6V6s served as line drivers to drive pulses through cables between rack assemblies.
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."
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 computer
A stored-program computer is a computer that stores program instructions in electronically, electromagnetically, or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechani ...
s that exist today, ENIAC was just a large collection of arithmetic machines, which originally had programs set up into the machine by a combination of
plugboard wiring and three portable function tables (containing 1,200 ten-way switches each). 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. 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.
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. The programmers were often able to narrow bugs down to an individual failed tube which could be pointed to for replacement by a technician.
Programmers
During
World War II
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, while the
U.S. Army needed to compute ballistics trajectories, many women were interviewed for this task. At least 200 women were hired by the
Moore School of Engineering to work as "
computer
A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s" and six of them were chosen to be the programmers of ENIAC.
Betty Holberton,
Kay McNulty,
Marlyn Wescoff,
Ruth Lichterman,
Betty Jean Jennings, and
Fran Bilas programmed the ENIAC to perform calculations for ballistics trajectories electronically for the Army's
Ballistic Research Laboratory.
While men having the same education and experience were designated "professionals", these women were designated "subprofessionals", though they had professional degrees in mathematics and were highly trained mathematicians.
These women were not "refrigerator ladies", i.e., models posing in front of the machine for press photography, as then computer scientist undergrad
Kathryn Kleiman discovered in her own research as opposed to what she was told by a historian in computing.
However, some of the women did not receive recognition for their work on the ENIAC in their entire lifetimes. After the war ended, the women continued to work on the ENIAC. Their expertise made their positions difficult to replace with returning soldiers. Later in the 1990s, Kleiman learned that most of the ENIAC programmers were not invited to the ENIAC’s 50th anniversary event. So she made it her mission to track them down and record their oral histories. "They were shocked to be discovered," Kleiman says. "They were thrilled to be recognized, but had mixed impressions about how they felt about being ignored for so long."
Kleiman released a book on the six female ENIAC programmers in 2022.
These early programmers were drawn from a group of about two hundred women employed as
computers
A computer is a machine that can be programmed to automatically carry out sequences of arithmetic or logical operations ('' computation''). Modern digital electronic computers can perform generic sets of operations known as ''programs'', ...
at the
Moore School of Electrical Engineering at the University of Pennsylvania. The job of computers was to produce the numeric result of mathematical formulas needed for a scientific study, or an engineering project. They usually did so with a mechanical calculator. The women studied the machine's logic, physical structure, operation, and circuitry in order to not only understand the mathematics of computing, but also the machine itself. This was one of the few technical job categories available to women at that time.
Betty Holberton (née Snyder) continued on to help write the first generative programming system (
SORT/MERGE) and help design the first commercial electronic computers, the
UNIVAC
UNIVAC (Universal Automatic Computer) was a line of electronic digital stored-program computers starting with the products of the Eckert–Mauchly Computer Corporation. Later the name was applied to a division of the Remington Rand company and ...
and the
BINAC
BINAC (Binary Automatic Computer) is an early electronic computer that was designed for Northrop Corporation, Northrop Aircraft Company by the Eckert–Mauchly Computer Corporation (EMCC) in 1949. J. Presper Eckert, Eckert and Mauchly had started ...
, alongside Jean Jennings.
McNulty developed the use of
subroutine
In computer programming, a function (also procedure, method, subroutine, routine, or subprogram) is a callable unit of software logic that has a well-defined interface and behavior and can be invoked multiple times.
Callable units provide a ...
s in order to help increase ENIAC's computational capability.
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. 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 language
A programming language is a system of notation for writing computer programs.
Programming languages are described in terms of their Syntax (programming languages), syntax (form) and semantics (computer science), semantics (meaning), usually def ...
s 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, McNulty, Jennings, Snyder, Wescoff, Bilas, and Lichterman have since been recognized for their contributions to computing.
Three of the current (2020) Army supercomputers, ''Jean'', ''Kay'', and ''Betty,'' are named after
Jean Bartik (Betty Jennings),
Kay McNulty, and
Betty Snyder respectively.
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. 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. 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."
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
Gloria Ruth Gordon.
Adele Goldstine wrote the original technical description of the ENIAC.
Programming languages
Several language systems were developed to describe programs for the ENIAC, including:
Role in the hydrogen bomb
Although the Ballistic Research Laboratory was the sponsor of ENIAC, one year into this three-year project
John von Neumann
John von Neumann ( ; ; December 28, 1903 – February 8, 1957) was a Hungarian and American mathematician, physicist, computer scientist and engineer. Von Neumann had perhaps the widest coverage of any mathematician of his time, in ...
, a mathematician working on the
hydrogen bomb
A thermonuclear weapon, fusion weapon or hydrogen bomb (H-bomb) is a second-generation nuclear weapon design. Its greater sophistication affords it vastly greater destructive power than first-generation nuclear bombs, a more compact size, a lo ...
at
Los Alamos National Laboratory, became aware of the ENIAC. In December 1945, the ENIAC was used to calculate
thermonuclear reactions using
equation
In mathematics, an equation is a mathematical formula that expresses the equality of two expressions, by connecting them with the equals sign . The word ''equation'' and its cognates in other languages may have subtly different meanings; for ...
s. The data was used to support research on building a hydrogen bomb.
Role in development of the Monte Carlo methods
Related to ENIAC's role in the hydrogen bomb was its role in the
Monte Carlo method
Monte Carlo methods, or Monte Carlo experiments, are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results. The underlying concept is to use randomness to solve problems that might be ...
becoming popular. Scientists involved in the original nuclear bomb development used massive groups of people doing huge numbers of calculations ("computers" in the terminology of the time) to investigate the distance that neutrons would likely travel through various materials.
John von Neumann
John von Neumann ( ; ; December 28, 1903 – February 8, 1957) was a Hungarian and American mathematician, physicist, computer scientist and engineer. Von Neumann had perhaps the widest coverage of any mathematician of his time, in ...
and
Stanislaw Ulam realized the speed of ENIAC would allow these calculations to be done much more quickly.
The success of this project showed the value of Monte Carlo methods in science.
Later developments
A press conference was held on February 1, 1946, and the completed machine was announced to the public the evening of February 14, 1946, 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. The machine was formally dedicated the next day 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.
The original contract amount was $61,700; the final cost was almost $500,000 (approximately ). 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
Aberdeen Proving Ground (APG) is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work at APG. There are 11 major commands among the tenant units, ...
,
Maryland
Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...
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.
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",
the Pentagon
The Pentagon is the headquarters building of the United States Department of Defense, in Arlington County, Virginia, across the Potomac River from Washington, D.C. The building was constructed on an accelerated schedule during World War II. As ...
invited "the top people in electronics and mathematics from the United States and Great Britain"
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.
Half of these lectures were given by the inventors of ENIAC.
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
EDVAC, which would be both simpler and more powerful. In particular, in 1944 Eckert wrote his description of a memory unit (the mercury
delay line) which would hold both the data and the program. John von Neumann, who was consulting for the Moore School on the EDVAC, sat in on the Moore School meetings at which the stored program concept was elaborated. Von Neumann wrote up an incomplete set of notes (''
First Draft of a Report on the EDVAC'') which were intended to be used as an internal memorandum—describing, elaborating, and couching in formal logical language the ideas developed in the meetings. ENIAC administrator and security officer
Herman Goldstine distributed copies of this ''First Draft'' to a number of government and educational institutions, spurring widespread interest in the construction of a new generation of electronic computing machines, including
Electronic Delay Storage Automatic Calculator (EDSAC) at Cambridge University, England and
SEAC at the U.S. Bureau of Standards.
Improvements
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,
after which programming was done by setting the switches. 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, and it was included in the ENIAC
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an sufficiency of disclosure, enabling discl ...
. Clippinger consulted with von Neumann on what instruction set to implement.
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, which made possible programming through the reader from standard IBM cards. The "first production run" of the new coding techniques on the
Monte Carlo
Monte Carlo ( ; ; or colloquially ; , ; ) is an official administrative area of Monaco, specifically the Ward (country subdivision), ward of Monte Carlo/Spélugues, where the Monte Carlo Casino is located. Informally, the name also refers to ...
problem followed in April. 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.
The programming of the stored program for ENIAC was done by Betty Jennings, Clippinger, Adele Goldstine and others.
It was first demonstrated as a
stored-program computer
A stored-program computer is a computer that stores program instructions in electronically, electromagnetically, or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechani ...
in April 1948, 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
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.
Comparison with other early computers

Mechanical computing machines have been around since
Archimedes
Archimedes of Syracuse ( ; ) was an Ancient Greece, Ancient Greek Greek mathematics, mathematician, physicist, engineer, astronomer, and Invention, inventor from the ancient city of Syracuse, Sicily, Syracuse in History of Greek and Hellenis ...
' time (see:
Antikythera mechanism
The Antikythera mechanism ( , ) is an Ancient Greece, Ancient Greek hand-powered orrery (model of the Solar System). It is the oldest known example of an Analog computer, analogue computer. It could be used to predict astronomy, astronomical ...
), but the 1930s and 1940s are considered the beginning of the modern computer era.
ENIAC was, like the IBM
Harvard Mark I and the German
Z3, able to run an arbitrary sequence of mathematical operations, but did not read them from a tape. Like the British
Colossus, it was programmed by plugboard and switches. ENIAC combined full,
Turing-complete programmability with electronic speed. The
Atanasoff–Berry Computer (ABC), ENIAC, and Colossus all used
thermionic valves (vacuum tubes). ENIAC's registers performed decimal arithmetic, rather than binary arithmetic like the Z3, the ABC and Colossus.
Like the Colossus, ENIAC required rewiring to reprogram until April 1948. In June 1948, the
Manchester Baby ran its first program and earned the distinction of first electronic
stored-program computer
A stored-program computer is a computer that stores program instructions in electronically, electromagnetically, or optically accessible memory. This contrasts with systems that stored the program instructions with plugboards or similar mechani ...
. 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
Iowa State University was stopped in 1942 after
John Atanasoff was called to
Washington, D.C., to do physics research for the U.S. Navy, and it was subsequently dismantled. The Z3 was destroyed by the Allied bombing raids of Berlin in 1943. As the ten Colossus machines were part of the UK's war effort their existence remained secret until the late 1970s, although knowledge of their capabilities remained among their UK staff and invited Americans. ENIAC, by contrast, was put through its paces for the press in 1946, "and captured the world's imagination". Older histories of computing may therefore not be comprehensive in their coverage and analysis of this period. All but two of the Colossus machines were dismantled in 1945; the remaining two were used to decrypt Soviet messages by
GCHQ
Government Communications Headquarters (GCHQ) is an intelligence and security organisation responsible for providing signals intelligence (SIGINT) and information assurance (IA) to the government and armed forces of the United Kingdom. Primar ...
until the 1960s. The public demonstration for ENIAC was developed by Snyder and Jennings who created a demo that would calculate the trajectory of a missile in 15 seconds, a task that would have taken several weeks for a
human computer.
Patent
For a variety of reasonsincluding Mauchly's June 1941 examination of the
Atanasoff–Berry computer (ABC), prototyped in 1939 by
John Atanasoff and
Clifford Berry for ENIAC, applied for in 1947 and granted in 1964, was voided by the 1973 decision of the landmark federal court case ''
Honeywell, Inc. v. Sperry Rand Corp.''. The decision included: that the ENIAC inventors had derived the subject matter of the electronic digital computer from Atanasoff; gave legal recognition to Atanasoff as the inventor of the first electronic digital computer; and put the invention of the electronic digital computer in the
public domain
The public domain (PD) consists of all the creative work to which no Exclusive exclusive intellectual property rights apply. Those rights may have expired, been forfeited, expressly Waiver, waived, or may be inapplicable. Because no one holds ...
.
Main parts
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.
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).
* 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) in the
National Museum of American History
The National Museum of American History: Kenneth E. Behring Center is a historical museum in Washington, D.C. It collects, preserves, and displays the heritage of the United States in the areas of social, political, cultural, scientific, and m ...
in Washington, D.C. (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).
* The
University of Michigan
The University of Michigan (U-M, U of M, or Michigan) is a public university, public research university in Ann Arbor, Michigan, United States. Founded in 1817, it is the oldest institution of higher education in the state. The University of Mi ...
in Ann Arbor has four panels (two accumulators, High-speed Multiplier panel 3, and Master Programmer panel 2), salvaged by
Arthur Burks.
* The
United States Army Ordnance Museum
The United States Army Ordnance Training Support Facility (formerly known as the U.S. Army Ordnance Training and Heritage Center and U.S. Army Ordnance Museum) artifacts are used to train and educate logistic soldiers. It re-located to Fort Gre ...
at
Aberdeen Proving Ground
Aberdeen Proving Ground (APG) is a U.S. Army facility located adjacent to Aberdeen, Harford County, Maryland, United States. More than 7,500 civilians and 5,000 military personnel work at APG. There are 11 major commands among the tenant units, ...
,
Maryland
Maryland ( ) is a U.S. state, state in the Mid-Atlantic (United States), Mid-Atlantic region of the United States. It borders the states of Virginia to its south, West Virginia to its west, Pennsylvania to its north, and Delaware to its east ...
, where ENIAC was used, has Portable Function Table A.
* The U.S. Army Field Artillery Museum in
Fort Sill
Fort Sill is a United States Army post north of Lawton, Oklahoma, about 85 miles (137 km) southwest of Oklahoma City. It covers almost .
The fort was first built during the Indian Wars. It is designated as a National Historic Landmark a ...
, as of October 2014, obtained seven panels of ENIAC that were previously housed by The Perot Group in Plano, Texas. There are accumulators #7, #8, #11, and #17; panel #1 and #2 that connected to function table #1, 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) (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.
Recognition
ENIAC was named an
IEEE Milestone in 1987.
In 1996, in honor of the ENIAC's 50th anniversary, The
University of Pennsylvania
The University of Pennsylvania (Penn or UPenn) is a Private university, private Ivy League research university in Philadelphia, Pennsylvania, United States. One of nine colonial colleges, it was chartered in 1755 through the efforts of f ...
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.
In 1997, the six women who did most of the programming of ENIAC were inducted into the
Technology International Hall of Fame.
The role of the ENIAC programmers is treated in a 2010 documentary film titled ''
Top Secret Rosies: The Female "Computers" of WWII'' by LeAnn Erickson.
A 2014 documentary short, ''The Computers'' by Kate McMahon, tells of the story of the six programmers; this was the result of 20 years' research by Kathryn Kleiman and her team as part of the ENIAC Programmers Project.
In 2022
Grand Central Publishing released ''Proving Ground'' by Kathy Kleiman, a hardcover biography about the six ENIAC programmers and their efforts to translate block diagrams and
electronic schematics of the ENIAC, then under construction, into programs that would be loaded into and run on ENIAC once it was available for use.
In 2011, in honor of the 65th anniversary of the ENIAC's unveiling, the city of Philadelphia declared February 15 as ENIAC Day.
The ENIAC celebrated its 70th anniversary on February 15, 2016.
See also
*
History of computing
*
History of computing hardware
The history of computing hardware spans the developments from early devices used for simple calculations to today's complex computers, encompassing advancements in both analog and digital technology.
The first aids to computation were purely mec ...
*
Women in computing
Women in computing were among the first programmers in the early 20th century, and contributed substantially to the industry. As technology and practices altered, the role of women as programmers has changed, and the recorded history of the fi ...
*
List of vacuum-tube computers
*
List of military electronics of the United States
*
Military computers
*
Unisys
Unisys Corporation is a global technology solutions company founded in 1986 and headquartered in Blue Bell, Pennsylvania. The company provides cloud, AI, digital workplace, logistics, and enterprise computing services.
History Founding
Unis ...
*
Arthur Burks
*
Betty Holberton
*
Frances Bilas Spence
*
John Mauchly
John William Mauchly ( ; August 30, 1907 – January 8, 1980) was an American physicist who, along with J. Presper Eckert, designed ENIAC, the first general-purpose electronic digital computer, as well as EDVAC, BINAC and UNIVAC I, the f ...
*
J. Presper Eckert
*
Jean Jennings Bartik
*
Kathleen Antonelli (Kay McNulty)
*
Marlyn Meltzer
*
Ruth Lichterman Teitelbaum
Notes
References
*
*
*
original source
*
*
*
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
John William Mauchly ( ; August 30, 1907 – January 8, 1980) was an American physicist who, along with J. Presper Eckert, designed ENIAC, the first general-purpose electronic digital computer, as well as EDVAC, BINAC and UNIVAC I, the f ...
, 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)
*
original source* (also reprinted in ''The Origins of Digital Computers: Selected Papers'', Springer-Verlag, New York, 1982, pp. 359–373)
*
*
*
*
*
*
Mauchly, John, ''The ENIAC'' (in Metropolis, Nicholas,
Howlett, Jack; Rota, Gian-Carlo. 1980, ''A History of Computing in the Twentieth Century'',
Academic Press
Academic Press (AP) is an academic book publisher founded in 1941. It launched a British division in the 1950s. Academic Press was acquired by Harcourt, Brace & World in 1969. Reed Elsevier said in 2000 it would buy Harcourt, a deal complete ...
, New York, , pp. 541–550, "Original versions of these papers were presented at the International Research Conference on the History of Computing, held at the
Los Alamos Scientific Laboratory, 10–15 June 1976.")
*
*
* Rojas, Raúl; Hashagen, Ulf, editors. ''The First Computers: History and Architectures'', 2000,
MIT Press
The MIT Press is the university press of the Massachusetts Institute of Technology (MIT), a private research university in Cambridge, Massachusetts. The MIT Press publishes a number of academic journals and has been a pioneer in the Open Ac ...
,
*
*
*
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)''
*
*
* Hally, Mike. ''Electronic Brains: Stories from the Dawn of the Computer Age'',
Joseph Henry
Joseph Henry (December 17, 1797– May 13, 1878) was an American physicist and inventor who served as the first secretary of the Smithsonian Institution. He was the secretary for the National Institute for the Promotion of Science, a precursor ...
Press, 2005.
*
* Tompkins, C. B.; Wakelin, J. H.; ''High-Speed Computing Devices'',
McGraw-Hill, 1950.
*
*
External links
ENIAC simulation3D printable model of the ENIAC*
ttp://americanhistory.si.edu/comphist/eckert.htm Interview with EckertTranscript 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 ProjectMike Muuss: Collected ENIAC documentschapter in Karl Kempf, ''Electronic Computers Within The Ordnance Corps'', November 1961
Martin H. Weik, Ordnance Ballistic Research Laboratories, 1961
at the University of Pennsylvania
from Ballistic Research Laboratories Report No. 971 December 1955, (A Survey of Domestic Electronic Digital Computing Systems)
Michael Kanellos, 60th anniversary news story, ''CNet'', February 13, 2006
1946 film restored, Computer History Archives Project
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