47 Fun Facts About ENIAC

What does the acronym ENIAC stand for?

ENIAC stood for Electronic Numerical Integrator and Computer; completed in late 1945 and announced in February 1946, it was the first programmable, electronic, general-purpose digital computer.

Which two men designed ENIAC?

Physicist John Mauchly proposed an electronic calculator in a 1942 memo and teamed with J. Presper Eckert, the young engineer who solved its reliability problems; Eckert was 24 when work began in 1943.

ENIAC was originally built to calculate what for the U.S. Army?

The Army's Ballistic Research Laboratory commissioned ENIAC to compute artillery firing tables, each trajectory of which took a human computer many hours; the war ended before the machine was finished.

What was the subject of ENIAC's first program?

Its first real job, run in December 1945 before the public unveiling, was a Los Alamos calculation on the feasibility of the hydrogen bomb, brought to the project by John von Neumann.

Where was ENIAC built and formally dedicated on February 15, 1946?

Work took place in secret at the Moore School of Electrical Engineering; Philadelphia declared February 15 ENIAC Day in 2011.

What nickname did the press give ENIAC when it was unveiled?

Newspapers hailed the machine as a 'Giant Brain' at its February 1946 unveiling; it was about a thousand times faster than the electromechanical calculators of the day.

What was the code name under which work on ENIAC began in secret in 1943?

Work began in secret under the code name Project PX after the Army contract was signed on June 5, 1943, with John Grist Brainerd as principal investigator and the Ballistic Research Laboratory paying.

How much did the Army's original six-month research contract for ENIAC pay the university?

The contract signed on June 5, 1943 paid $61,700 for six months of research and development; the project ran far longer and far over that budget before the machine was finished in late 1945.

Approximately how many vacuum tubes did ENIAC contain by the end of its operation?

ENIAC held 17,468 vacuum tubes by the end of its service, about 18,000, alongside 7,200 crystal diodes, 1,500 relays, 70,000 resistors and 10,000 capacitors.

How much electricity did ENIAC consume?

ENIAC drew about 150 kW, much of it heating the filaments of its vacuum tubes — enough to feed the rumour that Philadelphia's lights dimmed whenever it was switched on.

How many ten-digit accumulators did ENIAC have?

ENIAC had 20 accumulators, each able to hold and add or subtract a ten-digit signed decimal number; they could run in parallel for higher peak throughput.

How many simple additions or subtractions per second could an ENIAC accumulator perform?

An accumulator completed an addition or subtraction in one 200-microsecond machine cycle, that is 5,000 per second; the cycle was 20 pulses of the 100 kHz clock in the cycling unit.

How many multiplications per second could ENIAC perform at most?

ENIAC's multiplier, driving four accumulators, managed up to 385 ten-digit multiplications per second; division ran at about 40 per second and square roots at 3.

ENIAC's arithmetic units worked in which number system?

ENIAC worked in decimal: each digit lived in a ten-position ring counter of vacuum tubes that electronically imitated the digit wheels of a mechanical adding machine, unlike the binary Z3 and Atanasoff-Berry machines.

How many vacuum tubes were needed to store a single digit in ENIAC's ring counters?

Each decimal digit took 36 vacuum tubes, ten of which were the dual triodes forming the flip-flops of its ten-position ring counter, so a single ten-digit accumulator needed hundreds of tubes.

After engineers improved reliability, how often did an ENIAC tube fail, according to Eckert?

Eckert said that after the improvements a tube failed only about every two days and the fault could be located within 15 minutes; early on several tubes burned out daily, idling the machine half the time.

What was ENIAC's longest continuous run without a failure, recorded in 1954?

The record run in 1954 was 116 hours, close to five days, without a failure; special high-reliability tubes had not been available until 1948.

How was a program originally loaded into ENIAC?

Mapping a problem onto the machine usually took weeks, and physically setting the switches and cables could take days.

How many primary programmers did ENIAC have?

Six women were the primary programmers, chosen from the roughly 200 women the Moore School employed as human computers calculating ballistics tables by hand; they worked out the machine's logic from its wiring diagrams.

Which ENIAC programmer later helped write SORT/MERGE and design UNIVAC and BINAC?

Betty Holberton (née Snyder) went on to help design BINAC and UNIVAC, wrote the first sort-merge generator in 1951, and later served on the COBOL and FORTRAN standards committees.

How were the ENIAC programmers classified by the Army, despite holding mathematics degrees?

The Army classed the women as 'subprofessionals' while men with the same mathematics degrees were designated 'professionals'; some of the six were never recognised for their work in their lifetimes.

A historian once dismissed the women in ENIAC press photos as what?

Told by a computer historian that the women in the photos were 'Refrigerator Ladies' — models posed beside the machine — undergraduate Kathy Kleiman later tracked the six programmers down and recorded their oral histories.

Which two ENIAC programmers wrote the trajectory demonstration for the February 1946 press unveiling?

Betty Snyder and Betty Jean Jennings — later Holberton and Bartik — programmed the trajectory demonstration in the days before the February 1946 unveiling, yet none of the women were invited to the dedication or the dinner afterwards.

To which Army site was ENIAC moved in 1947, where it ran until 1955?

At the Ballistic Research Laboratory at Aberdeen Proving Ground, Maryland, the machine was switched back on on July 29, 1947 and ran until 11:45 p.m. on October 2, 1955.

ENIAC was retired in October 1955 in favour of which two more efficient computers?

EDVAC and ORDVAC, both stored-program machines running at the Ballistic Research Laboratory by the early 1950s, made ENIAC redundant; it was switched off on October 2, 1955.

Which mathematician wrote the 'First Draft of a Report on the EDVAC'?

John von Neumann wrote the First Draft in June 1945; though it drew on Eckert and Mauchly's EDVAC meetings, its circulation under his name alone put the stored-program design in the public domain and later helped void ENIAC's patent.

When ENIAC was converted to a primitive stored-program machine in 1948, what happened to its speed?

It was still worth it, because reprogramming now took hours instead of days and most real problems were I/O-bound anyway.

Which company built the 100-word magnetic-core memory added to ENIAC in 1953?

Burroughs Corporation built the 100-word magnetic-core memory added in 1953; it stored digits in excess-3 binary-coded decimal and needed three new orders in the programming mechanism.

Which statistical technique took off after von Neumann and Ulam realised ENIAC could run its calculations fast?

Stanislaw Ulam proposed the Monte Carlo method in 1946 and von Neumann saw that ENIAC could run its random-sampling calculations; the first Monte Carlo neutron-diffusion runs took place on ENIAC in 1948.

Which 1973 court case voided the ENIAC patent and named John Atanasoff inventor of the electronic digital computer?

Judge Earl Larson's October 1973 ruling in Honeywell v. Sperry Rand found the ENIAC patent derived from Atanasoff's work, which Mauchly had examined in June 1941, and put the electronic digital computer in the public domain.

Which British machine ran its first program in June 1948, becoming the first electronic stored-program computer?

The Manchester Baby, formally the Small-Scale Experimental Machine, ran its first program on June 21, 1948, the first electronic computer to execute a program held in its own memory; ENIAC had been rewired for each new problem until 1948.

How many Colossus codebreaking machines had Britain built, kept secret until the late 1970s?

All but two were dismantled in 1945; the last pair decrypted Soviet messages for GCHQ into the 1960s.

What did the Pentagon-sponsored 1946 course on electronic computer design become known as?

The Moore School Lectures, held July 8 to August 31, 1946 and sponsored by Army Ordnance and the Office of Naval Research, were the first course ever given on computer design; Eckert and Mauchly gave many of the talks.

What was the tiny 1996 chip built for the machine's 50th anniversary that reproduced its full functionality called?

ENIAC-on-a-Chip, built by Penn students under Jan Van der Spiegel for the 1996 anniversary, packed the whole machine into a 7.44 mm by 5.29 mm die of 174,569 transistors running at 20 MHz.

How many function tables did ENIAC have for holding constants and, later, programs?

ENIAC had three function tables, A, B and C, each holding 104 numbers set on banks of rotary switches; after the 1948 conversion they held the program's instruction codes.

In 1997 the six ENIAC programmers were inducted into which organisation's honour roll?

All six — Bartik, Holberton, Antonelli, Meltzer, Spence and Teitelbaum — were inducted into the Women in Technology International Hall of Fame in 1997, half a century after the machine's unveiling.

As a schoolboy, J. Presper Eckert spent afternoons in the laboratory of which television inventor?

As a teenager Eckert spent afternoons at Philo Farnsworth's television laboratory in Philadelphia's Chestnut Hill; he later placed second nationally on the College Board maths section and filed his first patent at 21.

Which content-management framework named its default theme 'Bartik' after ENIAC programmer Jean Bartik?

Drupal made Bartik the default theme of Drupal 7 in 2011, honouring Jean Bartik; born Betty Jean Jennings in Missouri, she was hired by Penn in 1945 to compute ballistics tables by hand.

Which Moore School Army liaison championed Eckert and Mauchly's electronic computer proposal in 1943?

Goldstine later selected the six programmers, whom he called operators, and circulated von Neumann's EDVAC report.

Roughly what did ENIAC cost in total, in 1940s dollars?

The final bill came to $486,804.22, about $487,000 in 1940s dollars — roughly eight times the $61,700 of the Army's original six-month contract — with the Ballistic Research Laboratory footing it.

How long was ENIAC, end to end, along its U-shaped row of panels?

ENIAC's 40 panels ran about 100 feet end to end, each roughly 8 feet tall and 3 feet deep, arranged in a U around a room of some 1,800 square feet.

Approximately how many hand-soldered joints did ENIAC contain by the end of its service?

ENIAC contained around 5,000,000 hand-soldered joints, alongside 17,468 vacuum tubes, 7,200 crystal diodes, 1,500 relays, 70,000 resistors and 10,000 capacitors.

Before joining the Moore School, John Mauchly taught physics at which Pennsylvania institution?

Mauchly headed the physics department at Ursinus College in Collegeville from 1933 to 1941, then took a Moore School summer course in electronics and stayed on as an instructor.

Who wrote the original technical description of ENIAC?

Adele Goldstine, a Moore School mathematics instructor, wrote the 1946 ENIAC Technical Report, the machine's original complete description; she also trained the six programmers and helped design the 1948 stored-program conversion.

Which engineer on the ENIAC team was responsible for its multiplier?

Arthur Burks designed ENIAC's multiplier; he later moved to Michigan, where four ENIAC panels he obtained for the university are displayed in Ann Arbor.

What is the title of Kathy Kleiman's 2022 biography of the six ENIAC programmers?

Proving Ground, published in 2022, grew out of Kleiman's two decades of interviews with the programmers; her 2014 documentary short The Computers told the story first.

Which 2010 documentary by LeAnn Erickson covers the ENIAC programmers' role?

Top Secret Rosies: The Female Computers of WWII, LeAnn Erickson's 2010 documentary, profiles the women hired to compute ballistics tables by hand, the job title the machine later took.