The personal computer

A personal computer is a complete, general-purpose computer priced and sized for a single owner. What made it possible was the microprocessor: once an entire central processor fit on one mass-produced chip costing tens of dollars, the surrounding machine — memory, a power supply, a case, some way to get data in and out — could be built cheaply enough for a hobbyist, then a household. The defining shift is not the hardware but the ownership. Where earlier computers were institutional, shared, and rationed, the personal computer put a reprogrammable, general-purpose machine under one person's sole control, available at any hour, to be bent to whatever that person wanted.

For thirty years, using a computer meant borrowing time on someone else's — a corporation's, a university's, a government's — through a queue, a terminal, or a stack of punched cards. Access was a privilege, mediated by operators and budgets. The personal computer dissolved that gatekeeping. A machine you owned outright could be experimented with freely, programmed at midnight, and used for purposes no institution would ever have authorized. That change in *access* is what let software become a mass creative medium rather than a specialist trade: millions of ordinary people could now write, tinker, and eventually buy programs, and a whole consumer software industry grew in the space the personal computer opened.

In late 1974 Ed Roberts, running a small Albuquerque electronics company called MITS, built a computer around Intel's new 8080 microprocessor and sold it by mail order as the Altair 8800. Its January 1975 appearance on the cover of *Popular Electronics* — the name suggested by an editor's daughter, after a *Star Trek* destination — drew a flood of orders that swamped the tiny firm. The Altair was barely usable alone: a front panel of switches and lamps, and hardly any memory. What made it matter was the ecosystem that rushed to fill the gaps — add-on memory boards, teletypes, and Gates and Allen's Altair BASIC, which let people write programs in words instead of switch-flips. Two years later the Apple II (1977) delivered the idea to the mass market: a pre-assembled machine with a keyboard, color graphics, and expansion slots that an ordinary buyer could plug in and use, no soldering required.

Word processors, spreadsheets, and games turned the personal computer from a hobbyist's curiosity into a fixture of offices and homes, and the software written to run on it became one of the largest industries on the planet. The same idea, shrunk further, is the laptop, the smartphone, and the tablet — each a personal, general-purpose computer descended directly from the desktop machine. And by putting a networkable computer in front of hundreds of millions of individuals, it supplied the other half of what the internet needed: not just a network, but a personal device on every desk and in every pocket to connect to it.