[HN Gopher] Eniac, the First General-Purpose Digital Computer, T...
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Eniac, the First General-Purpose Digital Computer, Turns 80
Author : baruchel
Score : 106 points
Date : 2026-03-19 05:53 UTC (17 hours ago)
(HTM) web link (spectrum.ieee.org)
(TXT) w3m dump (spectrum.ieee.org)
| rvz wrote:
| Unfortunately, if the subject doesn't have "AI", no one cares.
| xattt wrote:
| It has IA in its name so that must count for something.
| embedding-shape wrote:
| That's AI in Spanish, so checks out in large parts of the
| world :)
| gerikson wrote:
| > The computer contained about 18,000 vacuum tubes, which were
| cooled by 80 air blowers. More than 30 meters long, it filled a 9
| m by 15 m room and weighed about 30 kilograms. It consumed as
| much electricity as a small town.
|
| Surprisingly light though...
| ahartmetz wrote:
| The vacuum in the tubes weighs nothing, so they produce lift.
| gus_massa wrote:
| I still remember the CRT TV we had at home when I was kid. It
| was big but almost empty.
|
| Vacuum tubes break too often. Once per year? But if you have a
| thousand of them you have to change one very often. So I guess
| they have a lot of space for humans repairing it.
| adrian_b wrote:
| An obvious typo. It was tons, not kilograms.
|
| Perhaps AI aided?
| Rochus wrote:
| Eniac was indeed impressive and an important milestone. I
| recommend the 1999 book "ENIAC - The triumphs and tragedies of
| the world's first computer" by Scott McCartney which is both
| interesting to read and very informative. Also the review of the
| book by the late Jean Bartik, one of the "computers" and thus an
| eyewitnmess, is very interesting:
| https://web.archive.org/web/20221101120020/https://www.amazo....
|
| Though the article is very US focussed, keeping quiet that German
| engineer Konrad Zuse completed the Z3 in May 1941, five years
| before ENIAC, effectively creating the world's first working
| programmable and fully automatic digital computer. While ENIAC
| required days of manual cable patching to program, the Z3 was
| quickly programmed by a punched tape ("Lochstreifen"), and Zuse
| also has invented Plankalkul between 1942 and 1945, which is
| widely recognized as the world's first high-level programming
| language. The cooperation between Zuse and ETH Zurich eventually
| led to the first self-compiling compiler and eventually Algol 60
| (see "The European Side of the Last Phase of the Development of
| ALGOL 60" by Peter Naur in ACM SIGPLAN "History of Programming
| Languages" from 1978). And there was also the British Colossus,
| which was also a "programmable computer" and successfully
| utilized vacuum tubes for code-breaking by early 1944.
| mrob wrote:
| The Z3 was only general purpose by accident, and this was only
| discovered in 1997 (published 1998). [0] It's only of
| theoretical interest because the technique required is too
| inefficient for real-world applications.
|
| ENIAC is notable because it was the first intentionally general
| purpose computer to be built.
|
| [0] https://www.inf.fu-berlin.de/inst/ag-
| ki/rojas_home/documents...
| ahartmetz wrote:
| Still feels like history written by the victors (of WW2 and
| computing, eventually) in this case. If you want to be
| mathematically precise, it's been proven to be Turing-
| complete. If you want to use common sense (IMO better), it
| was one of the most significant leaps in automated
| computation and simply didn't need to do more for its
| intended applications. For conditional branches to make
| sense, you also need a fast temporary storage array (since it
| would be awfully slow running directly off tape like a Turing
| machine), and to realize that all that effort makes sense,
| you first need to play with a computer for a while and
| discover the new possibilities.
| adrian_b wrote:
| I do not think that it is right at all to say "intentionally
| general purpose computer".
|
| ENIAC was built for a special purpose, the computation of
| artillery tables.
|
| It was a bespoke computer built for a single customer: the
| United States Army's Ballistic Research Laboratory.
|
| This is why it has been designed as the digital electronic
| equivalent of the analog mechanical computers that were
| previously used by the Army and why it does not resemble at
| all what is now meant by "general-purpose computer".
|
| The computers of Aiken and Zuse were really intentionally
| general-purpose, their designers did not have in mind any
| specific computation, which is why they were controlled by a
| program memory, not by a wiring diagram.
|
| What you claim about Z3 being general purpose by accident
| does not refer to the intention of its designer, but only to
| the fact that its instruction set was actually powerful
| enough by accident, because at that early time it was not
| understood which kinds of instructions are necessary for
| completeness.
|
| All the claims made now about ENIAC being general-purpose are
| retroactive. Only after the war ended and the concept of a
| digital computer became well understood, the ENIAC was
| repurposed to also do other tasks than originally planned.
|
| The first truly general-purpose electronic digital computers
| that were intentionally designed to be so were those designed
| based on the von Neumann report.
|
| Before the completion of the first of those, there were
| general-purpose hybrid electronic-electromechanical digital
| computers, IBM SSEC being the most important of them, which
| solved a lot of scientific and technical problems, before
| electronic computers became available.
| rootbear wrote:
| A counter argument is that Mauchly was actually interesting
| in using computers for weather modeling and I'm sure that
| influenced the design of ENIAC. He could only get ENIAC
| funded if it was valuable to the war effort. I've read
| quite a lot about that machine and I'm not aware of any
| architectural features that were specific to ballistics
| calculations. This is unlike the British Colossus, another
| early computer, which was specifically designed for code
| breaking and wasn't general purpose.
|
| As for the objection that it wasn't stored program, I was
| interested to learn that it was converted to stored program
| operation after only two years or so of operation, using
| the constant table switches as the program store. But the
| Manchester Baby, which used the same memory for code and
| data was more significant in the history of stored program
| machines.
|
| On the general question of "first computer", I think the
| answer is whatever machine you want it to be if you heap
| enough conditional adjectives on it.
| Rochus wrote:
| > Mauchly was actually interesting in using computers for
| weather modeling and I'm sure that influenced the design
| of ENIAC
|
| True. Mauchly was a physics professor interested in
| meterology, and he knew that predicting the weather and
| calculating an artillery shell's flight are
| mathematically the same type of problem, which was
| important to get funding. In the fifties, Eniac was even
| used to calculate weather forecasts (see https://ams.conf
| ex.com/ams/2020Annual/webprogram/Manuscript/...). So
| these were just two related special problems, and it
| would be a stretch to interpret this as an intention to
| build a general-purpose computer. The latter had to wait
| until the sixties.
| Rochus wrote:
| > The Z3 was only general purpose by accident ... ENIAC [..]
| was the first intentionally general purpose computer
|
| That's a pretty academic take. Neither Eckert, nor Mauchly,
| nor Zuse knew about Alan Turing's 1936 paper when they
| designed their machines. The classification of ENIAC (and the
| Z3) as a "universal Turing machine" is entirely a retroactive
| reinterpretation by later computer scientists. John von
| Neumann knew the paper and was aware of its significance, but
| he only turned up in the ENIAC project when the design was
| complete. At this time, Eckert and Mauchly were already well
| aware of ENIAC's biggest flaw (the massive effort to
| reprogram the machine, and in fact they came up with the
| stored-program concept which von Neumann later formalized).
| ENIAC's funding and primary justification were for the very
| specific purpose of calculating artillery firing tables for
| the military. The machine was built for this purpose, which
| included the feature which retroactively led to the mentioned
| classification.
| yaakov34 wrote:
| The Z3 was not a general purpose computer; it was a calculator
| that performed a predetermined sequence of operations that was
| written to its tape. It was remarkable for being all-binary in
| an era when differential gears and cams were very common in
| computing devices, and had some other advanced features. But
| the 1990s article that declared it Turing-complete is just
| silly. It would apply to every four-function calculator that
| supports rounding, and programming a computer like that is not
| just "impractical" - both the tape and execution time would
| grow exponentially in number of branches - but it is not the
| model that Turing proposed. The whole point of Turing's
| (theoretical) device is that a short program using the
| abilities of that device could perform unlimited computations;
| if you make the program length unlimited instead, that's a much
| less interesting model of computation.
|
| The problem is that anything that gets into Wikipedia becomes
| ingrained in the Internet's collective mind, which then can't
| be changed.
| ogogmad wrote:
| Would it not have been easy to add branch instructions to it?
| Just rewind the instruction tape however many places. It
| seems 99% of the job was done.
| jcranmer wrote:
| There are three main problems with trying to offer a simple
| answer to the question of "what is the first computer?"
|
| The most obvious of the problems is that a computer isn't a
| singular technology that springs up de novo, but something that
| develops from antecedents over a long, messy transition problem
| that requires a judgement call as to when the proto-computer
| becomes an actual computer. A judgement call which is obviously
| going to be biased based on the other considerations. Consider,
| for a more contemporary example, what you would argue as the
| "first smartphone" or the "first LLM." Personally, I think the
| ENIAC is still somewhat too proto-computer for my tastes: I'd
| prefer a "first" that uses binary arithmetic and has stored
| programs, neither of which is true for the ENIAC.
|
| The second major issue is it's also instructive to look at the
| candidates' influence on later development. Among the
| contenders for "first computer," it's unfortunately kinda clear
| that ENIAC has the most lasting influence. ENIAC's development
| produced the papers that directly inspires the next generation
| of machines. Colossus is screwed here because of the secrecy of
| the code-breaking effort. Meanwhile, Zuse and Z3 suffer from
| being on the losing end of WW2. ABC has a claim here, but it's
| not clear whether or not the developers of ENIAC drew influence
| from ABC or not.
|
| The final major issue isn't so much an issue by itself but
| rather something that colors the interpretation of the first
| two issues: national pride. An American is far more likely to
| weight the influence and ingenuity of the ENIAC and similar
| machines to label one of them the "first computer." A UK person
| would instead prefer to crown Colossus or the Manchester Baby.
| A German would prefer the Z3.
| alephnil wrote:
| In many ways the ENIAC was more like an FPGA than a computer.
| It was programmed with patch cables connecting the different
| computational units as well as switches, and had no CPU as
| such. The cables had to be physically rerouted when changing
| to a new program, which took weeks. My understanding is that
| it was eventually programmed to emulate a von Neuman machine
| around 1948/49. As far as I understand, this was done mainly
| by Jean Bartik based on Von Neumans ideas.
|
| If this is correct, it was not a von Neuman machine
| originally, but it eventually became one, and at
| approximately the same time as the Manchester Baby.
| klelatti wrote:
| ENIAC was very important but this article overstates its
| significance and ignores other (non US) machines to the point of
| historical inaccuracy. No mention of Z3 or Manchester Baby for
| example, the latter based on the von Neumann paper for example,
| was arguably a more accurate pointer towards how computer
| architecture would develop.
| sebastos wrote:
| Wait, where are you thinking the von Neumann paper which came
| from?
| klelatti wrote:
| The paper came out of work on ENIAC and was adapted to follow
| the approach in the paper but Baby was built from outset to
| use that approach and its design much more closely matches
| the architecture that has been used by almost all digital
| computers since. I don't dispute that ENIAC is important but
| it's role is more nuanced than this article implies.
| BirAdam wrote:
| ENIAC was far more important for the general computing industry
| than other machines of its time. ENIAC led to EMCC (the first
| computer company) and UNIVAC. It was UNIVAC and IBM struggling
| against one another that created the entire industry.
| hedora wrote:
| IBM built the Harvard Mark 1 in 1944, before EMCC existed.
| adrian_b wrote:
| The shortened title is very incorrect.
|
| What the article says is different: "the first large-scale,
| general-purpose, programmable electronic digital computer".
|
| The claim of the article can be considered correct, and
| "electronic" is a part that cannot be deleted from it without
| falsifying the claim.
|
| Before ENIAC, there have been digital computers that were much
| more general-purpose, because they run programs written on
| punched tape, instead of requiring a rewiring like ENIAC.
|
| ENIAC, which evolved from the analog computers known as
| differential analyzers, had a structure closer to an FPGA than to
| a modern digital computer.
|
| In contrast, an earlier relay computer like Harvard Mark I was
| intended as a successor of the mechanical digital computer
| designed by Charles Babbage, so it already had the same structure
| with a modern digital computer, except that it used different
| kind of memories for data and for programs, hence the name
| "Harvard architecture". The same was true for the Zuse computer.
|
| The earlier ABC digital computer was electronic, but it can be
| considered as special-purpose, not general-purpose. The first
| relay computers at Bell Labs may also be considered as special
| purpose.
| mrob wrote:
| In this context, "general purpose" means "Turing complete" in
| the informal sense of handwaving away the requirement for
| infinite storage space.
| adrian_b wrote:
| What you say changes nothing.
|
| The earlier relay computers were Turing complete.
|
| For ENIAC it also does not make sense to claim that it was
| Turing complete. Such a claim can be made for a computer
| controlled by a program memory, where you have a defined
| instruction set, and the instruction set may be complete or
| not. If you may rewire arbitrarily the execution units, any
| computer is Turing complete.
|
| The earlier ABC electronic computer was built for a special
| purpose, the solution of systems of linear algebraic
| equations, like ENIAC was built only for a special purpose,
| the computation of artillery tables.
|
| By rewiring the ABC electronic computer you could have also
| computed anything, so you can say that it was Turing
| complete, if rewiring is allowed.
|
| The only difference is that rewiring was simpler in ENIAC,
| because it had been planned to be easy, so there were special
| panels where you could alter the connections.
|
| Neither ABC nor ENIAC had enough memory to be truly general-
| purpose, and by the end of the war it was recognized that
| this was the main limitation for extending the domain of
| applications, so the ENIAC team proposed ultrasonic delay
| lines as the solution for a big memory (inspired by the use
| of delay lines as an analog memory in radars), while von
| Neumann proposed the use of a cathode ray tube of the kind
| used in video cameras (iconoscope; this was implemented first
| in the Manchester computers).
|
| Because ENIAC was not really designed as general-purpose, its
| designers originally did not think about high-capacity
| memories. On the other hand, John Vincent Atanasoff, the main
| designer of the ABC computer, has written a very insightful
| document about the requirements for memories in digital
| computers, years before ENIAC, where he analyzed all the
| known possibilities and where he invented the concept of
| DRAM, but implemented with discrete capacitors. Later, the
| proposal of von Neumann was also to use a DRAM, but to use a
| cheaper and more compact iconoscope CRT, instead of discrete
| capacitors.
|
| While the ABC computer was not general-purpose as built, the
| document written by Atanasoff in 1940, "Computing Machine for
| the Solution of Large Systems of Linear Algebraic Equations",
| demonstrated a much better understanding of the concept of a
| general-purpose electronic digital computer than the
| designers of ENIAC would demonstrate before the end of 1944 /
| beginning of 1945, when they realized that a bigger memory is
| needed to make a computer suitable for any other
| applications, i.e. for really making it "general purpose".
| froh wrote:
| Zuse Z3 enters the room, relais' kindly rattling "Hrm. I was
| digital. not electronic as in cathode tubes but definitively
| digital."
| josefritzishere wrote:
| One of the engineers who worked on the Eniac lived next door to
| my old landlord in New Jersey. They played chess in the back
| yard. He was reputedly quite good.
| ux266478 wrote:
| For the curious programmers who are wondering what it was like to
| program ENIAC, a simulator is available:
|
| https://www.cs.drexel.edu/~bls96/eniac/simulator.html
|
| And a programming manual:
|
| https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=846...
|
| It's really got a nice archaic character.
| soyyo wrote:
| I find it interesting that, unless I'm mistaken, this was a
| completely engineering effort.
|
| That is, they were not trying to follow the notion of a universal
| computing device that had already been defined by Turing and
| Church at the time. They were just trying to build something like
| a huge programmable calculator, but they ended up building a
| universal computation device anyway.
| bpoyner wrote:
| Reminds me of stumbling across the Harvard Mark I, which is about
| 1-2 years older, while wandering through the Harvard Science
| Center (as one does). By far the oldest computer I've seen in
| person. Seems they moved it since then to the Science and
| Engineering Complex.
| llimllib wrote:
| My alma mater, Ursinus, is a very small school and has few claims
| to fame; but one of them is that John Mauchly taught there before
| going to Penn to design ENIAC. Wikipedia puts it bluntly:
|
| > Mauchly's teaching career truly began in 1933 at Ursinus
| College where he was appointed head of the physics department,
| where he was, in fact, the only staff member.
| hedora wrote:
| Arguably, it was the second.
|
| The Harvard Mark 1 ran its first program in 1944, but didn't have
| branches as we understand them until 1946:
|
| https://en.wikipedia.org/wiki/Harvard_Mark_I
|
| Apparently, you could achieve loops by taping the input program
| into a physical loop, even in 1944.
| LeFantome wrote:
| Colossus Mark I beat them too:
|
| https://en.wikipedia.org/wiki/Colossus_computer
| LeFantome wrote:
| Colossus was first:
|
| https://en.wikipedia.org/wiki/Colossus_computer
| DaleBiagio wrote:
| ENIAC is where the profession of programming was born -- and the
| first programmers were six women: Kay McNulty, Betty Jennings,
| Betty Snyder, Marlyn Meltzer, Frances Bilas, and Ruth Lichterman.
|
| They had to program it by physically rewiring patch cables and
| flipping switches. There was no programming language, no stored
| program. The "software" was the hardware configuration itself.
|
| It took another decade before FORTRAN (1957) gave programmers a
| way to write instructions in something resembling human language.
| LetsGetTechnicl wrote:
| Thank you for highlighting the contributions of women in
| computing, especially at it's inception! That is so easily
| forgotten or intentionally ignored in the age of the "tech bro"
| AnimalMuppet wrote:
| Even in the 1950s, my mother worked on a machine that could be
| programmed in octal, but you could change the instruction set
| with patch cables.
| JoeDaDude wrote:
| For a while I worked at what was then the Sperry Rand Corporation
| (now Unisys) which had some pride in their heritage as the
| descendant of the Univac Corporation founded by ENIAC inventors
| Eckert and Mauchly. In a glass case there was a vacuum tube
| circuit said to be a memory unit of the original ENIAC. No one
| seemed to know much about it, casting doubt on the claimed
| provenance of the device.
|
| The tube circuit resembled the ones shown in the photo linked
| below (although none of those in the photo are from ENIAC).
|
| https://en.wikipedia.org/wiki/File:Women_holding_parts_of_th...
| Finnucane wrote:
| "More than 30 meters long, it filled a 9 m by 15 m room and
| weighed about 30 kilograms."
|
| It was a balloon?
| jonjacky wrote:
| A newer book, from 2016, _ENIAC in Action: Making and Remaking
| the Modern Computer_ by Thomas Haigh, Mark Priestly, and Crispin
| Rope
|
| https://mitpress.mit.edu/9780262334433/eniac-in-action/
|
| An interesting revelation here is that, although ENIAC was not
| originally conceived as a stored program computer, it was quite
| early converted to one. They repurposed a lookup table intended
| to calculate functions to store instructions instead. Many of the
| well-known ENIAC calculations, such as Monte Carlo simulations,
| were programmed in this mode.
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