50 Fun Facts About ENIAC

What does the acronym ENIAC stand for?

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.

Which two men designed ENIAC?

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.

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

The customer was the Ballistic Research Laboratory, but the machine's first actual program was a study of the feasibility of the hydrogen bomb.

What was the subject of ENIAC's first program?

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.

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?

It was about a thousand times faster than the electro-mechanical machines of the day.

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

John Grist Brainerd was principal investigator, and Herman Goldstine had persuaded the Army to pay for it.

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

The final bill came to almost $500,000, roughly $9 million in today's money.

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

It also had 7,200 crystal diodes, 6,000 relays, 70,000 resistors, 10,000 capacitors and around five million hand-soldered joints.

Roughly how much did ENIAC weigh?

It was about 10 feet tall, 3 feet deep and 100 feet long, filling 300 square feet.

How much electricity did ENIAC consume?

Input came from an IBM card reader and output went to an IBM card punch, which could feed an IBM accounting machine for printing.

How many ten-digit accumulators did ENIAC have?

Each could add, subtract and hold a ten-digit signed decimal number, and they could be run in parallel for higher peak speed.

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

The basic machine cycle was 200 microseconds, driven by a 100 kHz clock in the cycling unit.

How many multiplications per second could ENIAC perform at most?

Multiplication used four accumulators under a special multiplier unit; division and square roots were far slower, at 40 and 3 per second.

ENIAC's arithmetic units worked in which number system?

Its ring counters electronically imitated the digit wheels of a mechanical adding machine, unlike the binary Z3, ABC and Colossus.

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

Ten of them were the dual triodes forming the flip-flops of the ten-position ring counter.

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

Early on tubes burned out almost daily, leaving the machine down about half the time; most failures came during warm-up and cool-down.

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

That is close to five days; 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?

They were chosen from about 200 women hired by the Moore School as human 'computers' calculating ballistics tables by hand.

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

Fellow programmer Kay McNulty developed the use of subroutines to stretch ENIAC's capabilities.

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

Men with the same education were designated 'professionals'; some of the women were never recognised for their work in their lifetimes.

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

Kathryn Kleiman discovered as an undergraduate that they were the programmers, and later tracked them down to record their oral histories.

Which two ENIAC programmers wrote the February 1946 press trajectory demo for which the Goldstines took credit?

None of the women were invited to the formal dedication or the celebratory dinner afterwards.

The 1946 press demonstration calculated a missile trajectory in how long?

ENIAC's public unveiling 'captured the world's imagination', while Colossus stayed secret until the late 1970s.

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

It was switched back on there on July 29, 1947, and ran continuously until 11:45 p.m. on October 2, 1955.

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

Both successors were stored-program machines, the design principle ENIAC had lacked because of its 1943 design freeze.

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

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.

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?

The expansion memory used binary-coded decimal in excess-3 representation 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?

The original bomb project had used rooms full of human computers to estimate how far neutrons would travel through materials.

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

Mauchly had examined the Atanasoff-Berry Computer in June 1941; the ruling 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?

ENIAC needed rewiring to reprogram until April 1948, when Adele Goldstine's program for von Neumann first ran from the function tables.

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 computer-design talks in Philadelphia become known as?

Half the lectures were given by ENIAC's inventors, and Eckert's biography credits them as the first course on computing topics.

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

It measured 7.44 mm by 5.29 mm and ran at 20 MHz, many times faster than the original but slow beside 1990s microprocessors.

The U.S. Army supercomputers named Jean, Kay and Betty were named to honour which people?

They commemorate Jean Bartik (Betty Jennings), Kay McNulty and Betty Snyder.

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

Their story is told in the 2010 documentary Top Secret Rosies and Kathy Kleiman's 2022 book Proving Ground.

What company did ENIAC's two inventors found in 1946 after resigning from the university?

They left over a patent dispute; the firm built BINAC and then UNIVAC, the first commercial computer in the U.S.

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

Eckert placed second in the country on the maths section of the College Board exam and applied for his first patent at 21.

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

Born Betty Jean Jennings in Missouri, she was turned down by IBM at 20 before Penn hired her 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?

That is about $7 million in 2024 money, and eight times the $61,700 the Army's original research contract had promised.

How long was ENIAC, end to end, at roughly 10 feet tall and 3 feet deep?

The machine occupied about 300 square feet and drew 150 kW, with an IBM card reader for input and a card punch for output.

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

Alongside its 18,000 vacuum tubes it held 7,200 crystal diodes, 6,000 relays, 70,000 resistors and 10,000 capacitors.

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

Mauchly was not an electronics expert, which is why he partnered with the young engineer J. Presper Eckert to draft the machine.

Who wrote the original technical description of ENIAC?

After the first six programmers, an expanded team of about a hundred scientists was recruited to keep the machine working.

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

Burks later salvaged four ENIAC panels that are now held at the University of Michigan in Ann Arbor.

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

Kleiman's two decades of research also produced the 2014 documentary short about the same women.

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

Its full title calls the women 'The Female Computers of WWII', a nod to their original job title before the machine took the name.