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The TRS-80 Micro Computer System (TRS-80, later renamed the Model I to distinguish it from successors) is a desktop microcomputer launched in 1977 and sold by Tandy Corporation through their RadioShack stores. The name is an abbreviation of Tandy/RadioShack, Z80 microprocessor. It is one of the earliest mass-produced and mass-marketed retail home computers.The TRS-80 has a full-stroke QWERTY keyboard, the Zilog Z80 processor, 4 KB DRAM standard memory (when many 8-bit computers shipped with only 1 KB RAM), small size and desk footprint, floating-point Level I BASIC language interpreter in ROM, 64-character per line video monitor, and a starting price of US$600 (equivalent to US$2500 in 2020).
A cassette tape drive for program storage was included in the original base package, but it proved slow and fiddly in practice. While the software environment was stable and capable, the fiddly program load/save process combined with keyboard bounce issues and a troublesome expansion interface contributed to the Model I's widespread reputation as something fun to tinker with for computer enthusiasts, but not well suited to serious use. As with many small computers of the era, it lacked full support for the ASCII character set, e.g. no lowercase letters, which also hampered business adoption.
An extensive line of upgrades and add-on hardware peripherals for the TRS-80 was developed and marketed by Tandy/RadioShack. The basic system can be expanded with up to 48 KB of RAM (in 16 KB increments), and up to four floppy disk drives and/or hard disk drives. Tandy/RadioShack provided full-service support including upgrade, repair, and training services in their thousands of stores worldwide.
By 1979, the TRS-80 had the largest selection of software in the microcomputer market. Until 1982, the TRS-80 was the best-selling PC line, outselling the Apple II series by a factor of five according to one analysis.In mid-1980, the broadly compatible TRS-80 Model III was released. The Model I was discontinued shortly thereafter, primarily due to stricter FCC regulations on radio-frequency interference to nearby electronic devices. In April 1983, the Model III was succeeded by the compatible TRS-80 Model 4.
Following the original Model I and its compatible descendants, the TRS-80 name became a generic brand used on other unrelated computer lines sold by Tandy, including the TRS-80 Model II, TRS-80 Model 2000, TRS-80 Model 100, TRS-80 Color Computer and TRS-80 Pocket Computer.

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