how large was the eniac computer and how much memory did it have

ENIAC was enormous by modern standards: it filled roughly a room-sized area of about 1,800 square feet and weighed around 27–30 tons. Its original “memory” was not like modern RAM; it stored numbers in its accumulators and function tables, with a later addition of a 100-word magnetic-core memory in 1953.

How big was the ENIAC computer?

• ENIAC’s hardware was arranged in dozens of panels standing about 10 feet tall, around 3 feet deep, along a U-shaped layout roughly 100 feet long.

• Overall, it occupied about 1,800 square feet of floor space and weighed more than 27–30 tons, requiring about 150 kilowatts of power and extensive cooling.

Imagine a computer so large that it needed its own room, heavy structural support, and industrial-level power—closer to a small data center than a desktop PC.

How much memory did ENIAC have?

• ENIAC did not have RAM in the modern sense; it used 20 accumulators, each capable of holding a 10‑digit decimal number, plus additional registers and function tables for constants and lookup values.

• In 1953, engineers added a magnetic-core memory unit of 100 words, each word storing decimal data in a coded form, which significantly expanded how many values could be held internally at once.

What “memory” meant for ENIAC

• Early ENIAC memory was tied directly to its vacuum-tube accumulators and control circuits, so reprogramming often meant physically rewiring cables and switches rather than loading a program into addressable memory.

• Punch cards also served as an external storage medium, holding input data and results, functioning more like today’s disks than like true internal memory.

If a modern laptop casually uses gigabytes of RAM, ENIAC’s entire effective memory was closer to a handful of high-precision calculator registers plus a tiny add‑on core store.

Context for today’s readers

• Modern phones and laptops routinely have billions of bytes of RAM, whereas ENIAC’s original internal storage capacity was effectively only dozens of numbers, and even with the 100‑word core memory it remained extremely limited.

• Yet for the mid‑1940s, ENIAC’s speed and electronic design were revolutionary, enabling artillery calculations and scientific work that would otherwise have taken weeks or months by hand.

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ENIAC, one of the first electronic general-purpose computers, was a room‑sized giant weighing about 30 tons with roughly 1,800 square feet of hardware and only a handful of numerical registers plus a later 100‑word core memory—astonishingly small by modern standards.

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