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AiTechWorlds
AiTechWorlds
It is 1942. In a windowless room at an American university, rows of women sit at long tables. Each one holds a mechanical adding machine and a stack of printed forms. They are called "computers."
Not machines — people.
Their job title is "computer." Eight hours a day, they perform the same arithmetic operations over and over: logarithms for artillery firing tables, trajectory calculations for bombs, navigation figures for aircraft. One mistake and a pilot might fly the wrong course. The work is exhausting, relentless, and perfectly precise.
These women — many of them mathematicians hired because men were away at war — were so skilled and so fast that they were the gold standard of calculation. But even they had limits. A single complex trajectory calculation could take two to three days by hand.
The engineers watching them thought: there must be a better way.
That thought launched the computer revolution.
Understanding how computers evolved teaches you why they work the way they do. Every design decision made in 1945 still echoes in the laptop in front of you. The problems engineers faced then — speed, heat, size, cost, reliability — are the same problems engineers face today, just at a different scale.
Long before electricity, an English mathematician named Charles Babbage designed a mechanical calculator he called the Difference Engine in 1822. Powered by steam and made of brass gears, it was designed to automatically compute and print mathematical tables — eliminating human error from navigation charts and tax tables.
Babbage never finished building it in his lifetime (funding ran out and the engineering tolerances of the era were too crude). But the concept was revolutionary: a machine that could perform calculation automatically, step by step, following a plan.
In 1991, the Science Museum in London built Babbage's Difference Engine No. 2 from his original drawings. It worked perfectly — 170 years after he designed it.
Ada Lovelace, daughter of the poet Lord Byron, worked with Babbage on his more ambitious follow-up design, the Analytical Engine. In 1843, she translated an Italian article about the Analytical Engine and added her own extensive notes — which ended up three times longer than the original article.
In those notes, Lovelace described an algorithm for the machine to calculate Bernoulli numbers. It is widely recognised as the first computer program ever written — written for a machine that was never built.
She also wrote something extraordinary for 1843:
"The Analytical Engine has no power of originating anything. It can only do what we know how to order it to perform."
That insight — that a computer executes instructions but does not think independently — remains fundamentally true today.
The Harvard Mark I, completed in 1944, was the first large-scale electromechanical computer in the United States. Built by IBM under contract for the US Navy, it was a staggering physical object:
The clicking and clattering of its relays could be heard from outside the building. It was programmed by feeding it punched paper tape — long rolls of tape with holes punched in specific positions to represent instructions.
Its most famous early operator was Grace Hopper, a Navy officer and mathematician who would later invent the first compiler and popularise the term "debugging" (she literally removed a moth stuck in one of the Mark I's relays in 1947).
The Electronic Numerical Integrator and Computer (ENIAC), completed in 1945 at the University of Pennsylvania, was the first general-purpose electronic computer — using electronic vacuum tubes instead of mechanical relays. This made it vastly faster.
| Specification | Value |
|---|---|
| Vacuum tubes | 17,468 (often cited as ~18,000) |
| Floor space | ~167 square metres (half a basketball court) |
| Weight | ~27,000 kilograms |
| Construction cost | ~$487,000 (roughly $8 million in 2024 dollars) |
| Speed | 5,000 additions per second |
| Power consumption | ~150 kilowatts |
ENIAC was 1,000 times faster than the electromechanical Harvard Mark I. It could calculate a missile trajectory in 30 seconds — a task that took human computers 20 hours.
The problem with vacuum tubes: they burned out constantly — like light bulbs. With 18,000 tubes, at least one failed approximately every two days. Technicians were on permanent standby with replacement tubes. The machines also generated enormous heat and consumed electricity like a small neighbourhood.
In 1947, three physicists at Bell Laboratories — William Shockley, John Bardeen, and Walter Brattain — invented the transistor. They won the Nobel Prize in Physics for it in 1956.
A transistor does the same job as a vacuum tube (switching electrical signals on and off) but is:
Computers like the IBM 1401 (1959) used transistors and could be rented by businesses. For the first time, computing was not just for governments and universities — businesses could use computers for payroll, inventory, and bookkeeping.
In 1958, Jack Kilby at Texas Instruments (and independently, Robert Noyce at Fairchild Semiconductor) invented the integrated circuit (IC) — multiple transistors, resistors, and capacitors fabricated together on a single piece of semiconductor material (silicon).
Instead of wiring together thousands of individual transistors by hand, an IC packed them all onto one chip the size of a fingernail.
The IBM System/360 was the landmark product of this era. It was a family of compatible computers — from small machines for businesses to large machines for scientific computing — that all ran the same software. This was revolutionary: you could write a program once and run it on any System/360.
It used IC chips and introduced the concept of software compatibility across hardware lines — a concept so important it still defines the computer industry today (your iPhone app runs on iPhone 6 through iPhone 16).
In 1971, Intel released the 4004 — the world's first commercially available microprocessor. It packed an entire CPU onto a single chip measuring just 12mm × 6.3mm.
It was originally designed for a Japanese calculator company (Busicom). Its processing power was equivalent to ENIAC — the room-sized machine from 1945 — but it fit on your fingertip and cost $200.
| Year | Event |
|---|---|
| 1975 | Altair 8800 — first personal computer kit (inspired Bill Gates and Paul Allen to found Microsoft) |
| 1976 | Apple I — designed by Steve Wozniak, sold by Steve Jobs |
| 1977 | Apple II — first mass-market personal computer with color graphics |
| 1981 | IBM PC — standardised the personal computer platform |
| 1984 | Apple Macintosh — first mass-market GUI computer |
| 1991 | World Wide Web opens to the public |
| 1995 | Windows 95 — personal computing goes mainstream globally |
In 1965, Gordon Moore — co-founder of Intel — made an observation that became a self-fulfilling prophecy:
"The number of transistors on a microchip doubles approximately every two years, while the cost is halved."
This is Moore's Law — not a law of physics, but an observed trend that the semiconductor industry used as a target for decades.
Moore's Law held remarkably well for 50 years. Today, physical limits of silicon are slowing the doubling pace — but the spirit continues through 3D chip stacking, new materials, and parallel processing.
The 5th generation is defined not by a single hardware technology but by a goal: making computers that can reason, learn, and respond to natural language.
| Generation | Technology | Key Example | Year | Key Characteristic |
|---|---|---|---|---|
| 0 | Electromechanical relays | Harvard Mark I | 1944 | Room-sized, noisy, slow |
| 1st | Vacuum tubes | ENIAC | 1945 | Electronic, but hot and unreliable |
| 2nd | Transistors | IBM 1401 | 1959 | Smaller, faster, business use begins |
| 3rd | Integrated circuits | IBM System/360 | 1964 | Software compatibility, mass adoption |
| 4th | Microprocessors | Intel 4004 / IBM PC | 1971 | Personal computers, internet era |
| 5th | AI / Quantum | Deep Blue / GPT-4 | 1997–now | Machine learning, natural language |
Here is a fact that puts everything into perspective:
The Apollo Guidance Computer (AGC) that landed humans on the Moon in 1969 had:
Your smartphone (e.g., iPhone 16 Pro, 2024) has:
Your phone has more computing power than all of NASA's computers combined during the entire Apollo program.
And it fits in your pocket. And it costs less, in real terms, than a good pair of shoes.
That is the story of computing — relentless, breathtaking progress, driven by curious people refusing to accept "this is good enough."
Next Lesson: All modern computers share one fundamental design — conceived by a single mathematician in 1945. Meet John von Neumann and the architecture that every computer still uses today.
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