50 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 50 questions with answers and explanations. Play the quiz
Q 01What does the acronym ENIAC stand for?
Electronic Numerical Integrator and Computer
Wikipedia calls it the first programmable, electronic, general-purpose digital computer; other machines had some of those features, but it was the first with all of them.
Q 02Which two men designed ENIAC?
John Mauchly and J. Presper Eckert
Mauchly was a physics professor at Ursinus College who was not an electronics expert, so he teamed up with Eckert, an engineer at Penn's Moore School.
Q 03ENIAC was originally built to calculate what for the U.S. Army?
Artillery firing tables
The customer was the Ballistic Research Laboratory, but the machine's first actual program was a study of the feasibility of the hydrogen bomb.
Q 04What was the subject of ENIAC's first program?
The feasibility of the hydrogen bomb
John von Neumann, working on the H-bomb at Los Alamos, learned about the machine a year into the project and got it running thermonuclear equations in December 1945.
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
It was about a thousand times faster than the electro-mechanical machines of the day.
Q 07What was the code name under which work on ENIAC began in secret in 1943?
Project PX
John Grist Brainerd was principal investigator, and Herman Goldstine had persuaded the Army to pay for it.
Q 08How much did the Army's original six-month research contract for ENIAC pay the university?
$61,700
The final bill came to almost $500,000, roughly $9 million in today's money.
Q 09Approximately how many vacuum tubes did ENIAC contain by the end of its operation?
18,000
It also had 7,200 crystal diodes, 6,000 relays, 70,000 resistors, 10,000 capacitors and around five million hand-soldered joints.
Q 10Roughly how much did ENIAC weigh?
More than 30 short tons
It was about 10 feet tall, 3 feet deep and 100 feet long, filling 300 square feet.
Q 11How much electricity did ENIAC consume?
150 kW
Input came from an IBM card reader and output went to an IBM card punch, which could feed an IBM accounting machine for printing.
Q 12How many ten-digit accumulators did ENIAC have?
20
Each could add, subtract and hold a ten-digit signed decimal number, and they could be run in parallel for higher peak speed.
Q 13How many simple additions or subtractions per second could an ENIAC accumulator perform?
5,000
The basic machine cycle was 200 microseconds, driven by a 100 kHz clock in the cycling unit.
Q 14How many multiplications per second could ENIAC perform at most?
Q 21Which ENIAC programmer later helped write SORT/MERGE and design UNIVAC and BINAC?
Betty Holberton
Fellow programmer Kay McNulty developed the use of subroutines to stretch ENIAC's capabilities.
Q 22How were the ENIAC programmers classified by the Army, despite holding mathematics degrees?
Subprofessionals
Men with the same education were designated 'professionals'; some of the women were never recognised for their work in their lifetimes.
Q 23A historian once dismissed the women in ENIAC press photos as what?
Refrigerator ladies
Kathryn Kleiman discovered as an undergraduate that they were the programmers, and later tracked them down to record their oral histories.
385
Multiplication used four accumulators under a special multiplier unit; division and square roots were far slower, at 40 and 3 per second.
Q 15ENIAC's arithmetic units worked in which number system?
Decimal
Its ring counters electronically imitated the digit wheels of a mechanical adding machine, unlike the binary Z3, ABC and Colossus.
Q 16How many vacuum tubes were needed to store a single digit in ENIAC's ring counters?
36
Ten of them were the dual triodes forming the flip-flops of the ten-position ring counter.
Q 17After engineers improved reliability, how often did an ENIAC tube fail, according to Eckert?
About every two days
Early on tubes burned out almost daily, leaving the machine down about half the time; most failures came during warm-up and cool-down.
Q 18What was ENIAC's longest continuous run without a failure, recorded in 1954?
116 hours
That is close to five days; special high-reliability tubes had not been available until 1948.
Q 19How 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 20How many primary programmers did ENIAC have?
Six
They were chosen from about 200 women hired by the Moore School as human 'computers' calculating ballistics tables by hand.
Q 24Which two ENIAC programmers wrote the February 1946 press trajectory demo for which the Goldstines took credit?
Betty Snyder and Betty Jean Jennings
None of the women were invited to the formal dedication or the celebratory dinner afterwards.
Q 25The 1946 press demonstration calculated a missile trajectory in how long?
15 seconds
ENIAC's public unveiling 'captured the world's imagination', while Colossus stayed secret until the late 1970s.
Q 26To which Army site was ENIAC moved in 1947, where it ran until 1955?
Aberdeen Proving Ground, Maryland
It was switched back on there on July 29, 1947, and ran continuously until 11:45 p.m. on October 2, 1955.
Q 27ENIAC was retired in October 1955 in favour of which two more efficient computers?
EDVAC and ORDVAC
Both successors were stored-program machines, the design principle ENIAC had lacked because of its 1943 design freeze.
Q 28Which mathematician wrote the 'First Draft of a Report on the EDVAC'?
John von Neumann
Herman Goldstine circulated the incomplete notes widely, spurring EDSAC at Cambridge and SEAC at the Bureau of Standards, and helping to void ENIAC's patent.
Q 29When 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 30Which company built the 100-word magnetic-core memory added to ENIAC in 1953?
Burroughs Corporation
The expansion memory used binary-coded decimal in excess-3 representation and needed three new orders in the programming mechanism.