When a Computer Filled a Whole Room

The story

Pick up a phone and feel how light it is. It slips into a pocket. Now let me tell you about one of the first electronic computers, a machine so big that nobody could pick it up at all. To visit it, you stepped into the room it filled.

Around eighty years ago, in an American city called Philadelphia, engineers built a machine called ENIAC. It stretched along the walls of a large room. It weighed about thirty tonnes, as much as five elephants standing together. Inside it glowed nearly eighteen thousand glass tubes, each one like a small hot lamp, and together they drank so much electricity that the room grew warm. ENIAC's job was doing sums. Enormous, difficult sums that would take a person with a pencil many months, ENIAC could finish in hours.

But a machine that big had big troubles too. Those glowing tubes kept burning out, the way light bulbs do, and engineers walked the aisles hunting for the dead one. And ENIAC did not run itself. Among its first programmers were six clever women, and to give the machine a new job, they replugged thick cables and set hundreds of switches and dials, like operators rewiring a whole telephone exchange.

Here is a story from those room-sized days. In another famous computer lab, a machine stopped working properly, and when the team searched inside, they found the trouble: a real moth, stuck in the works. Machine problems already had the nickname bugs, so the team taped the moth into their logbook and joked that this time, they had found an actual bug. People fixing computers still call it debugging.

So how did a thirty-tonne room shrink into a pocket? Inventors found a way to do a glass tube's job with a tiny electronic switch called a transistor, small as a crumb, with no glowing heater and far less heat. Then they learned to build thousands of transistors together on one small chip, then millions. Today, a chip about the size of your fingernail can carry BILLIONS of transistors, together doing the switching work that whole walls of glowing glass tubes once did in that warm room in Philadelphia.

That may be the fastest shrinking act in history. A machine that once filled a room and needed a team of people to run it now slips into a pocket, runs on a little battery, and does sums millions of times faster than ENIAC ever could.

So the next time you see someone tap a phone, picture the room it came from: the warm glowing tubes, the humming cables, the engineers walking the aisles of their gigantic computer. The computer never stopped working. It just kept shrinking, year after year, until it fitted inside a hand.