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47 free ENIAC trivia questions with answers — technology quiz, new questions added Aug 2026.
This ENIAC trivia quiz is about the 30-ton, 18,000-tube machine that the press called a 'Giant Brain' when it was unveiled at the University of Pennsylvania in February 1946. It covers how the Army came to fund John Mauchly and J. Presper Eckert's secret Project PX to speed up artillery firing tables, what the machine was actually made of, how fast it could add, multiply and divide, and how often a tube burned out. A large part of the quiz is devoted to the six women, Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Wescoff, Fran Bilas and Ruth Lichterman, who worked out how to program the thing with cables and switches, and who were left off the guest list for its own dedication dinner. It also asks about ENIAC's first real job for the hydrogen bomb, its role in the Monte Carlo method, its 1948 conversion into a slow stored-program computer, its retirement at Aberdeen in 1955, and the 1973 court ruling that voided its patent in favour of John Atanasoff. Difficulty runs from easy questions about what the acronym stands for to expert questions on accumulators and ring counters. Every answer was verified against the Wikipedia articles on ENIAC, J. Presper Eckert and Jean Bartik.
30 of 47 questions with answers and explanations. Play the quiz
Q 01What does the acronym ENIAC stand for?
Electronic Numerical Integrator and Computer
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.
Q 02Which two men designed ENIAC?
John Mauchly and J. Presper Eckert
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.
Q 03ENIAC was originally built to calculate what for the U.S. Army?
Artillery firing tables
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.
Q 04What was the subject of ENIAC's first program?
The feasibility of the hydrogen bomb
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.
Q 05Where was ENIAC built and formally dedicated on February 15, 1946?
Penn's Moore School
Work took place in secret at the Moore School of Electrical Engineering; Philadelphia declared February 15 ENIAC Day in 2011.
Q 06What nickname did the press give ENIAC when it was unveiled?
Giant Brain
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.
Q 07What was the code name under which work on ENIAC began in secret in 1943?
Project PX
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.
Q 08How much did the Army's original six-month research contract for ENIAC pay the university?
$61,700
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.
Q 09Approximately how many vacuum tubes did ENIAC contain by the end of its operation?
18,000
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.
Q 10How much electricity did ENIAC consume?
150 kW
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.
Q 11How many ten-digit accumulators did ENIAC have?
20
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.
Q 12How many simple additions or subtractions per second could an ENIAC accumulator perform?
5,000
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.
Q 13How many multiplications per second could ENIAC perform at most?
385
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.
Q 21How were the ENIAC programmers classified by the Army, despite holding mathematics degrees?
Subprofessionals
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.
Q 22A historian once dismissed the women in ENIAC press photos as what?
Refrigerator ladies
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.
Q 23Which two ENIAC programmers wrote the trajectory demonstration for the February 1946 press unveiling?
Q 14ENIAC's arithmetic units worked in which number system?
Decimal
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.
Q 15How many vacuum tubes were needed to store a single digit in ENIAC's ring counters?
36
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.
Q 16After engineers improved reliability, how often did an ENIAC tube fail, according to Eckert?
About every two days
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.
Q 17What was ENIAC's longest continuous run without a failure, recorded in 1954?
116 hours
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.
Q 18How was a program originally loaded into ENIAC?
By plugboard wiring and setting switches on function tables
Mapping a problem onto the machine usually took weeks, and physically setting the switches and cables could take days.
Q 19How many primary programmers did ENIAC have?
Six
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.
Q 20Which ENIAC programmer later helped write SORT/MERGE and design UNIVAC and BINAC?
Betty Holberton
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.
Betty Snyder and Betty Jean Jennings
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.
Q 24To which Army site was ENIAC moved in 1947, where it ran until 1955?
Aberdeen Proving Ground, Maryland
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.
Q 25ENIAC was retired in October 1955 in favour of which two more efficient computers?
EDVAC and ORDVAC
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.
Q 26Which mathematician wrote the 'First Draft of a Report on the EDVAC'?
John von Neumann
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.
Q 27When ENIAC was converted to a primitive stored-program machine in 1948, what happened to its speed?
It fell by a factor of six
It was still worth it, because reprogramming now took hours instead of days and most real problems were I/O-bound anyway.
Q 28Which company built the 100-word magnetic-core memory added to ENIAC in 1953?
Burroughs Corporation
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.
Q 29Which statistical technique took off after von Neumann and Ulam realised ENIAC could run its calculations fast?
The Monte Carlo method
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.
Q 30Which 1973 court case voided the ENIAC patent and named John Atanasoff inventor of the electronic digital computer?
Honeywell v. Sperry Rand
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.