Honestly, if you ask three different historians "how was the first computer made," you’re going to get four different answers. It’s a bit of a nightmare to pin down because "first" is a loaded word. Are we talking about something mechanical? Something electronic? Something that could actually store a program? If we’re looking for the birth of the modern digital age, we usually land on a rainy day in Philadelphia during the mid-1940s.
The ENIAC—the Electronic Numerical Integrator and Computer—is the beast most people point to. But it wasn't built in a sleek Silicon Valley garage. It was born in the basement of the Moore School of Electrical Engineering at the University of Pennsylvania. It was loud. It was hot. It was practically a living, breathing creature made of glass and wire.
The Secret War Project That Changed Everything
You have to understand the context. It was World War II. The U.S. Army needed to calculate artillery firing tables. These were basically massive books of math that told soldiers where to aim their big guns based on wind, humidity, and distance. Before the ENIAC, these were calculated by hand by "computers"—which, back then, was a job title for people, mostly women, who were wizards at math.
It was slow. Too slow. One trajectory took about 40 hours to calculate by hand. The Army was desperate. So, they funded a wild proposal by John Mauchly and J. Presper Eckert. They wanted to build a machine that used vacuum tubes—the same stuff in old radios—to do the math at the speed of light. Or at least, at the speed of electrons.
Building a Room-Sized Brain
So, how was the first computer made in a physical sense? It wasn't "made" so much as it was "assembled" on a terrifying scale. We are talking about 17,468 vacuum tubes. These things are fragile. They’re like lightbulbs. If one blew, the whole calculation could fail. People often joke that the lights in Philadelphia dimmed whenever they turned it on. That’s probably a myth, but it consumed 150 kilowatts of power, which is enough to run a small neighborhood.
The construction was a logistical mess. They used:
- 70,000 resistors
- 10,000 capacitors
- 1,500 relays
- 6,000 manual switches
- 5 million hand-soldered joints
Imagine soldering five million points. Your back would never be the same. Eckert was the engineering genius here; he was obsessed with reliability. He ran the vacuum tubes at lower voltages than they were rated for so they wouldn't burn out as fast. It worked, mostly. But even then, several tubes popped every single day. Finding the dead one was like looking for a needle in a haystack of glowing glass.
It Wasn't Just Hardware: The Forgotten Programmers
Here is what most people get wrong. They think the "making" of the computer ended when the last wire was soldered. It didn't. A computer is just a very expensive space heater if you don't tell it what to do.
The first "programmers" were six women: Kay McNulty, Betty Jennings, Marlyn Wescoff, Ruth Lichterman, Elizabeth Bilas, and Adele Goldstine. They didn't have "coding" languages. There was no Python. There was no C++. To program the ENIAC, they had to physically pull cables and flip switches. It was more like wiring a telephone switchboard than typing on a laptop. They had to map out the math on paper and then physically reconstruct the machine's logic every time they wanted to run a new problem.
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Why the "First" Computer is a Contentious Topic
If you’re a real tech nerd, you’re probably screaming "What about the Colossus?" or "What about the Z3?" and you’re right. History is rarely a straight line.
- The Z3 (1941): Built by Konrad Zuse in Germany. It was the first functional, programmable, fully automatic digital computer. But it was mechanical/electromechanical, not fully electronic, and it was destroyed in a bombing raid.
- The Atanasoff-Berry Computer (ABC): Built at Iowa State. It used vacuum tubes first, but it wasn't "programmable" in the way we think. It did one thing: linear equations. A court case in 1973 actually stripped the ENIAC of its patent, declaring Atanasoff the inventor of the "electronic digital computer."
- Colossus (1943): The British code-breaker. It was electronic and did amazing work at Bletchley Park, but it was kept top-secret until the 70s, so it didn't influence the commercial computer boom.
So, when we ask how the first computer was made, we’re usually looking at the ENIAC because it was the one that survived the war and showed the world what was possible. It was the ancestor of the UNIVAC, which eventually led to the computers we use today.
The Physicality of 1940s Engineering
You couldn't just "buy" parts. Most of the components were repurposed from other industries. They used IBM card readers for input and output because that was the only standard that existed. The whole thing was 80 feet long and weighed 30 tons. It took up a room that was 30 by 50 feet.
The heat was oppressive. Because those 17,000 tubes were basically little heaters, the room stayed well over 100 degrees Fahrenheit. They had to install massive blowers to keep the air moving so the solder wouldn't melt. It was a brutal environment for a "knowledge" job.
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The Shift to Stored Programs
The biggest flaw in how the first computer was made? It couldn't store its own instructions. If you wanted to change from calculating a missile trajectory to calculating weather patterns, you had to spend days unplugging and replugging the machine.
This changed with the EDVAC and the Manchester Baby. They realized the "program" could be stored in memory just like the "data." That was the "Aha!" moment. Once they figured out how to store bits in mercury delay lines or cathode ray tubes, the physical "making" of computers changed from rewiring hardware to writing software.
The Legacy of the Solder
We think of computers as "virtual" things now. We think of the Cloud. But the story of the first computer is a story of heavy metal, hot glass, and burned fingers. It was an industrial achievement as much as a mathematical one.
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The ENIAC was finally turned off in 1955. By then, it had done more math than all of humanity had performed up to that point. It proved that electronic pulses could replace human thought for the "grunt work" of logic.
Moving Forward: How to Explore This History Yourself
If you want to really understand the scale of how the first computer was made, you don't just read about it; you look at the architecture.
- Visit the Source: Parts of the ENIAC are still on display at the University of Pennsylvania and the Smithsonian. Seeing the scale of the vacuum tube racks in person changes your perspective on your smartphone.
- Study the Logic: Look into "Boolean Logic." It’s the simple True/False (1/0) system that the ENIAC used to turn those thousands of tubes into a functioning calculator.
- Acknowledge the Labor: Research the "ENIAC Six." Their contributions were ignored for decades because they were seen as "sub-professional" labor, even though they were essentially inventing the field of software engineering.
- Compare the Hardware: A modern greeting card that plays music has more computing power than the ENIAC did. But the ENIAC had to happen so the greeting card could exist.
The first computer wasn't made by a single person in a moment of "Eureka!" It was hammered out of necessity, funded by war, and kept running by people who weren't afraid to get their hands dirty with 30 tons of hot, glowing machinery.