Discovery — ENIAC (1945)
ENIAC (Electronic Numerical Integrator and Computer), designed by John Mauchly and J. Presper Eckert at the Moore School of Electrical Engineering, was commissioned by the US Army (Ballistic Research Laboratory) to compute artillery firing tables. Computing a single trajectory takes ENIAC 30 seconds, compared to 20 hours for a human calculator.
Machine Parameters
| Parameter | Value |
|---|---|
| Completion date | November 1945 (unveiled February 1946) |
| Location | University of Pennsylvania, Philadelphia |
| Vacuum tubes | 17,468 |
| Weight | 27 tonnes |
| Floor space | 167 m² (~15 × 9 m) |
| Power consumption | 150 kW |
| Speed | 5,000 additions/s, 357 multiplications/s |
| Cost | $487,000 (~$7M adjusted 2024) |
| Key innovation | First fully electronic and programmable calculator |
Technical Explanation — Electronic Computation
Before ENIAC, complex calculations were performed by human computers (often women mathematicians) or electromechanical machines (relays). Zuse's Z3 (1941) used relays; the British Colossus (1944) broke codes but was not general-purpose.
1. Vacuum tubes as switches — Each tube functions as an electronic switch: on/off in ~1 µs (vs ~10 ms for a mechanical relay). This 10,000× speed improvement over relays enables high-speed computation, but generates heat and frequent failures (~1 tube failing every 2 days).
2. Decimal architecture — ENIAC calculates in base 10 (not binary). Each decimal digit is represented by a ring of 10 vacuum tubes (ring counter). This wastes tubes but simplifies interfacing with human-scale problems.
3. Programming by wiring — The machine is programmed by physically reconnecting cables and adjusting ~3,000 switches. The six programmers (Kay McNulty, Betty Jennings, Betty Snyder, Marlyn Meltzer, Fran Bilas, Ruth Lichterman) had to understand the machine at the circuit level for each program. This process took days.
4. The von Neumann architecture (1945) — John von Neumann, consultant on the project, writes the EDVAC report proposing the stored program concept: instructions and data in the same memory, read sequentially. ENIAC itself was modified in 1948 to partially operate on this principle.
Why It Worked
The main challenge was reliability: 17,468 tubes with a high individual failure rate. Eckert solved the problem by running the tubes at reduced voltage (well below their rated capacity), reducing thermal stress and extending lifespan. Result: mean time between failures went from 15 minutes to several days.
Causal Chain
ENIAC (1945) → Von Neumann architecture / EDVAC (1949) → Commercial computers (UNIVAC I, 1951) → Transistorization (1950s) → Integrated circuits (1958) → Microprocessor (Intel 4004, 1971) → PC (1980s) → Internet/Web → Smartphone → AI
The Six Forgotten Programmers
The six women who programmed ENIAC were not recognized until 1997, when Kathy Kleiman rediscovered their names. They had developed the first concepts of subroutines and debugging — without documentation or training, by studying the electrical schematics directly.
Legacy and Current Data
ENIAC launched the computing era. The von Neumann architecture, formalized during the project, remains the dominant paradigm 80 years later. Computing power has increased by a factor of ~10¹⁰ since then.
Sources
References verified during the August 2026 fact-checking audit: these are the pages
against which this bulletin's claims were checked.