The year 1977 is the moment the personal computer stopped being a kit for hobbyists and became a finished product anyone could buy. Three machines reached the market that year, each sold as a complete unit with a keyboard and a ready-to-use BASIC, and they are remembered together as the 1977 trinity: the Apple II, the Commodore PET, and the Radio Shack TRS-80. Their own manuals, preserved in archives, document how each turned the new microprocessors into a consumer product.
The Apple II is documented in the Apple II Reference Manual, published by Apple Computer in January 1978, which describes a complete 6502 home computer with BASIC in firmware, color graphics, and internal expansion slots, sold in a molded case with a built-in keyboard. It was the most expandable and, with VisiCalc, eventually the most software-rich of the three.
The Commodore PET was the all-in-one machine of the group. The PET 2001-8 Personal Computer User Manual, issued by Commodore, documents a self-contained design that combined the computer, a keyboard, a display, and a cassette tape drive in a single case, so a buyer needed nothing else to start computing. Like the Apple II, it was built on a 6502-family processor and shipped with BASIC ready to run.
The TRS-80 brought the personal computer to a national retail chain. The TRS-80 Model I Preliminary Users Manual, the original manual Radio Shack shipped with the first machines in 1977, documents the low-cost system sold through Radio Shack’s thousands of stores. That retail reach made the TRS-80 one of the best-selling early machines and put computers in front of customers who would never have visited a specialty electronics shop.
The significance of the 1977 trinity is that, in a single year, three different companies independently proved that a fully assembled personal computer was a real and salable product. Between Apple’s expandable design, Commodore’s all-in-one package, and Radio Shack’s mass retail distribution, they established the personal computer as a mainstream consumer category and set the terms for the industry that exploded over the following decade.