Ah, Radio Shack. Once upon a time, it sold computers under its very own brand. And they were hugely successful. In the 1970s, when cassette tapes, and not floppy disks, were the go-to storage medium for computers, Tandy put out a personal computer called the TRS-80. Thanks to the TRS-80, the Tandy name was as big as IBM or Apple or Commodore in the PC market of the 1980s.
The TRS-80 launched in 1977, before the home computer market had really exploded. Tandy offered its first model with 4K of RAM, a 1.77 MHz processor and a 12-inch monitor for $600. Later models and a $300 Expansion Interface greatly increased the computer's capabilities, adding floppy support, extra ports and more memory [source: Goldklang].
Tandy's TRS-DOS (disk operating system) was a popular OS predating MS-DOS. Microsoft's early operating system bore some similarities to TRS-DOS -- no surprise, since Tandy sold more than 200,000 units and followed the TRS-80's success with more popular systems such as the 1980 Color Computer, or CoCo [source: Old Computers].