Before the PC: The World's First Digital Computer 'ENIAC' and the World of Computing Transformed by Vacuum Tubes - Memories of the Dawn of the PC

When that machine started up, the whole neighborhood would have a power outage.

It sounds like a B-movie, but this was an urban legend that was truly whispered in 1940s America. The culprit's name was ENIAC. It was the world's first general-purpose electronic computer, the ancestor of the computers we use today.
Weighing in at a staggering 30 tons and taking up the space of an entire house, the roots of the smartphone we carry in our pockets today were a surprisingly gluttonous, clumsy, and unimaginably huge 'monster'.

What flickered in the heart of this monster was the 'vacuum tube'. Why did these glass bulbs, which we now only see in retro audio amplifiers, become the protagonists that paved the way for the modern IT society?
Behind it lay the gritty tenacity of engineers and a major turning point in history where we steered from analog to digital.

The day humanity, tired of gear wear, bet on the speed of electricity

Before ENIAC was born, when people thought of computers, they meant mechanical ones with interlocking gears or analog ones that calculated based on voltage levels. For measuring 'continuous changes' in the natural world, such as tides or artillery trajectories, analog computers were very intuitive and convenient.

However, they had a fatal weakness. Gears wear out the more they are used, and voltage inevitably fluctuates due to heat and noise in the circuits. In other words, 'vague errors' would creep into the calculation results. Faced with the military demand to fire artillery further and more accurately, these errors became an issue that could not be ignored.

So, humanity decided to dare to abandon the smooth changes of the real world and simplify things. This was the birth of the digital world—a discontinuous world of '0 or 1' and 'current flowing or not flowing'.

At first, components called 'relays' were used, which physically clicked on and off. However, there is a speed limit to mechanical movement. We wanted to calculate faster, overwhelmingly faster. It was the vacuum tube that answered that desire. It had no moving parts inside and controlled the current solely through the movement of electrons flying through a glass tube. With the adoption of these 'glowing switches,' calculation speeds jumped thousands of times over in one fell swoop.

A 150-square-meter madness where the room itself was the brain

And so, in 1946, ENIAC was born at the University of Pennsylvania in the United States. Its appearance was far removed from the computers of today.

Imagine a scene where about 18,000 vacuum tubes were packed tightly onto panels covering an entire wall. The power consumption was 150 kilowatts. This is the level of electricity that dozens of modern average households would use at the same time. Naturally, the room was enveloped in tremendous heat, and it is said that the room temperature rose to nearly 50 degrees Celsius even when it wasn't summer. Engineers would sweat as they tended to the giant monster's moods.

However, its performance was literally revolutionary. ENIAC processed ballistic calculations that had previously taken human mathematicians 20 hours of desperate work in just 30 seconds. Since it takes about 30 seconds for an artillery shell to land after being fired, the calculation was finished while the shell was still in flight.

Until then, 'computer' was a 'human job title' for someone who sat hunched over a desk moving a slide rule. But faced with the overwhelming power of ENIAC, that word was completely overwritten as the 'name of a machine'.
The way businesses and organizations operate is fundamentally changed by technology. This was a paradigm shift that could truly be called the original DX.

In a room without a keyboard, committing to the cables

If a modern IT engineer were to time-travel to the era of ENIAC, they would surely despair. Because there was no concept of 'writing source code,' nor was there even 'memory' to store it.

What did the engineers do when they wanted to perform a different calculation? They spent days manually plugging and unplugging thousands of jumper cables into giant panels and turning dials one by one to reconfigure the 'physical circuits.' Programming was literally the act of wiring itself.

Supporting this grueling and meticulous work were six women who had previously been recruited as human computers. They deciphered the blueprints and, literally crawling around, searched for which holes to plug the cables into to get the correct answer.

Furthermore, operation was a series of troubles. With a high probability of one tube failing every few hours, a vacuum tube somewhere would make a popping sound and reach the end of its life. Every time the system came to a sudden halt, technicians had to dive into the vast sea of circuits and visually search for the burnt-out glass tube.

Just as modern engineers look at screen logs to find bugs, the technicians of that time were fighting against 'physical lightbulb burnouts.' Don't you think it was a rather gritty, yet deeply human workplace?

A Gift to the Future Left by a Monster's Weakness

The era of ENIAC and vacuum tubes did not last long. The weakness of being 'huge, hot, and prone to breaking' was, in other words, an intense homework assignment for humanity.

The obsession of engineers to somehow overcome this weakness eventually gave birth to the small 'transistor' that replaced the vacuum tube. And that led to the 'IC (Integrated Circuit)' that packs them onto a single board.
If the clumsy monster called ENIAC had not shown us the possibilities of the future with its overwhelming calculation speed, humanity would likely not have tried so desperately to shrink components.

We can now search for information from all over the world and connect with someone with just a fingertip. That is nothing other than the result of the footsteps of our predecessors who were running around in that sweltering room, searching for burnt-out vacuum tubes.

When your smartphone gets a little warm, it might not be a bad idea to feel the shadow of the 30-ton monster that once filled an entire room on the other side of that small screen.

Photo Source Information

・ ENIAC-01

・ENIAC-02

[Random Notes] The Era of ENIAC and Vacuum Tubes

1. [Technological Transition] The Revolution from Analog to Digital

This era was the moment a paradigm shift occurred from analog computers, which calculated using 'continuous quantities' such as length and voltage, to computers that processed using 'discrete values (digital)' of 0 and 1.

(1) From 'Gears and Circuits' to 'Electron Movement'
・Previous computers calculated by turning gears (such as the Difference Engine) or measuring the strength of voltage (analog quantities) like a differential analyzer.
・ENIAC achieved overwhelming ultra-high speed by electronically creating the digital state of electrical ON/OFF (switching).

(2) The Revolutionary Switch Called the 'Vacuum Tube'
・There were digital computers that used physically moving 'relays' (electromagnetic switches), but they had speed limitations.
・By adopting the 'vacuum tube,' which has no mechanical moving parts, the speed of current switching jumped by several thousand times.

2. [Birth of a Monster Machine] ENIAC's Specs and Overwhelming Scale

Here are facts showing the scale of how extraordinary the world's first general-purpose electronic computer, 'ENIAC,' was.

(1) The massive 'room' itself was the computer
- Total weight: Approximately 27 to 30 tons
- Installation area: Approximately 150 square meters (equivalent to a typical detached house or a large office floor)

(2) The heat and power emitted by 18,000 vacuum tubes
- It was composed of approximately 18,000 vacuum tubes, 70,000 resistors, and 10,000 capacitors.
- Power consumption was approximately 150 kW (more than several dozen typical modern households).
- It was so intense that an urban legend emerged that 'the whole room would get extremely hot and the surrounding city would suffer a power outage' when it was operated.

(3) Phenomenal calculation speed
- It was developed for the purpose of ballistic calculations (determining where a cannonball would land).
- It astonished people by completing in just '30 seconds' calculations that had previously taken human computers '20 hours'.

3. [The Struggles of the Dawn] Surprising Operational Realities and Programming

This is the behind-the-scenes look at the grueling operations of engineers at the time, which would be unimaginable to those using modern 'PCs'.

(1) Programming meant 'rewiring'
- At the time, there was no mechanism like today's where you could type code on a keyboard to store it (stored-program concept).
- To change the calculation content, engineers had to physically plug and unplug countless cables in front of a massive panel and turn dials (preparation alone could take several days).

(2) The daily occurrence of 'vacuum tube lifespan (bugs)'
- Vacuum tubes would reach the end of their lifespan at a rate of one every few hours, bursting or burning out.
- Every time the calculation stopped, engineers had to visually or manually search through the vast circuitry to find 'which vacuum tube had blown.' This was literal 'hardware maintenance'.

4. [Legacy for the Modern Age] Impact on Business, IT, and Society

This perspective explores how this era connects to the later 'PC dawn (1970s onwards)' and today's IT society.

(1) From 'Computer' as a human job title to the name of a machine
Originally, 'computer' was a term referring to 'human calculators' who performed manual calculations. After the advent of ENIAC, that role was completely replaced by machines.

(2) Bridging the gap from military to commerce and science
Although the technology started as a wartime ballistic calculator, it later became the foundation for data processing that supports business and society, such as weather forecasting, nuclear research, and population statistics.

(3) The origin of the passion for 'smaller and more reliable'
To overcome the biggest weaknesses—'vacuum tubes are huge, hot, and break easily'—the 'transistor' was later invented, which became the 'IC (integrated circuit)', and eventually became a single chip (CPU), leading to the miniaturization into the 'PC'. ENIAC's weaknesses were the biggest catalyst for technological evolution.

Related Articles

- The history and technological evolution of calculators and computers

Book Introduction

- Our PC 30-Year History: Nippon PC Chronicle Kindle Edition
Edited by SE Editorial Department
Shoeisha (2012/12/20)
A Japanese PC history textbook looking back with photos. It explains the major changes in PCs over more than 30 years in two parts, using many photos and touching on social conditions to make the flow of time easy to understand. Part 1 is dedicated to explaining topics by era, incorporating 'testimonies (turning points)' from developers and related parties at the time to reveal behind-the-scenes development stories. Part 2 summarizes PC architecture and other themes by topic.
(* Book descriptions, etc., are generally based on the descriptions on the linked site (Amazon). Please refer to the link for detailed content.)

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