TRS-80 Model I Family

The TRS-80 Model I computer, originally known as simply the TRS-80 computer, was released in 1977. It is considered to be part of the "1977 trinity of home computers also including the Apple II and the Commodore Pet. Unlike the 6502 driven Apple and Commodore machines, the Model I used the Zilog Z80 processor running at 1.77 MHz.

The original versions came with 4k RAM and Level I BASIC which was on Tiny Basic. In 1978, Level II Basic, a double precision floating point Basic written by Microsoft. Also, in 1978, the Expansion Interface was released. This Interface allowed up to four floppy disk drives and up to 48k RAM in groups of 16k assuming the base system had 16k installed. It also allowed a printer to be attached.

The second TRS-80 computer, the incompatible business computer Model II part of the TRS-80 Model II Family was released in 1979. It should be known that in 1978 a short-lived business system called the Tandy 10 Business Computer was released but it sold extremely poorly and to the best of my knowledge wasn't even featured in the famous Radio Shack Computer Catalogs. In 1980, it's mostly compatible successor the TRS-80 Model III was released. It was an all-in-system with a faster Z80 and the ability to type in lower case plus other improvements. Not long after, the FCC declared that the Model I did not comply to new, more stringent RF interference standard and Radio Shack had to take it off the market.

There are many good emulators for the system, but I recommend trs80gp which emulates multiple emulates all of the Z80 TRS-80 systems plus the Model 16, Tandy 6000, and the TRS-80 MC-10, a small, low price home computer.