Which Three PCs were released in 1977?

 

Answer:

The Commodore PET (Personal Electronic Transactor)

The Commodore PET (Personal Electronic Transactor) — the first of several personal computers released in 1977 — came fully assembled and was straightforward to operate, with either 4 or 8 kilobytes of memory, two built-in cassette drives, and a membrane "chiclet" keyboard.

 The Apple II

 The Apple II became an instant success when released in 1977 with its printed circuit motherboard, switching power supply, keyboard, case assembly, manual, game paddles, A/C powercord, and cassette tape with the computer game "Breakout." When hooked up to a color television set, the Apple II produced brilliant color graphics.

Tandy Radio Shack

 In the first month after its release, Tandy Radio Shack´s first desktop computer — the TRS-80 — sold 10,000 units, well more than the company´s projected sales of 3,000 units for one year. Priced at $599.95, the machine included a Z80 based microprocessor, a video display, 4 kilobytes of memory, BASIC, cassette storage, and easy-to-understand manuals that assumed no prior knowledge on the part of the consumer.