Computers are large, expensive machines for governments, universities, and major corporations. Personal computing is not practical.

For the first three decades of computing, the machines were the size of rooms. ENIAC, completed at the University of Pennsylvania in 1945, weighed 30 tons, stretched across 1,800 square feet of floor space, and required its own dedicated power supply. Through the 1960s, IBM's mainframes filled climate-controlled data centers and were operated by trained technicians who managed time on the machine for institutional users. The paradigm was institutional access, not individual ownership. Students learned that computers were tools for governments tracking census data, universities running research calculations, and corporations managing payroll for thousands of employees. The idea that an ordinary person might own and operate a computer at home seemed as practical as owning a power plant. If you graduated in 1977, this architecture seemed almost a feature of reality. Computation required infrastructure. Infrastructure required institutions. Personal computing was not a realistic vision for ordinary people.

Then three machines launched in the same summer. Apple Computer unveiled the Apple II at the West Coast Computer Faire in June 1977, fully assembled, color graphics, keyboard included, priced at $1,298. The machine was designed to connect to an ordinary television set. It came with BASIC programming in permanent memory, so users could start writing programs the moment they powered it on. Commodore released the PET 2001 the same month, with an integrated monitor and cassette tape drive for data storage. Tandy's TRS-80 arrived in August, sold through RadioShack stores, making it the first personal computer available through a national retail chain. Three affordable computers aimed at ordinary consumers appeared in the summer the 1977 graduating class was beginning their adult lives.

None of this was sudden. The Altair 8800, a kit computer for electronics hobbyists, had appeared on the cover of Popular Electronics in January 1975. It had no keyboard, no monitor, and required assembly from components, but it demonstrated that a sub-$500 computer was possible. Bill Gates and Paul Allen wrote a BASIC interpreter for it, founding Microsoft to distribute the software. Steve Jobs and Steve Wozniak built their first prototype in a garage after seeing the Altair prove the concept. Gordon Moore had described the underlying economic engine in 1965: the number of transistors on a chip was doubling roughly every two years, and cost per transistor was falling proportionally. The microprocessor, introduced by Intel in 1971, put an entire computer processor on a single chip. The pieces were visible to anyone watching closely, but the hobbyist movement existed in electronics magazines and garage workshops, not in institutional research that filtered into curricula. The classroom could see the current state of computing. It had no framework for Moore's trajectory.

Within a decade of 1977, personal computers were in millions of American homes and schools. The Apple II became the platform for VisiCalc, the first spreadsheet program, which turned the machine into a business tool that paid for itself in productivity gains. IBM entered the personal computer market in 1981, lending institutional credibility to what had been a hobbyist category. Programming became a professional skill sought across industries that had never imagined needing it. The machines were always going to get smaller and cheaper; the physics and economics of silicon had made that outcome almost certain years before anyone was teaching it. The classroom taught computing accurately for its moment. It taught the moment as if it were a destination.