The RadioShack TRS-80 Color Computer, later marketed as the Tandy Color Computer and sometimes nicknamed the CoCo, is a line of home computers developed and sold by Tandy Corporation. Despite sharing a name with the earlier TRS-80, the Color Computer is a completely different, incompatible system and a radical departure in design and compatibility with its Motorola 6809E processor rather than the Zilog Z80 earlier models were built around. The Tandy Color Computer line started in 1980 with what is now called the Color Computer 1. It was followed by the Color Computer 2 in 1983, then the Color Computer 3 in 1986. All three models maintain a high level of software and hardware compatibility, with few programs written for an older model being unable to run on the newer ones. The Color Computer 3 was discontinued in 1991. All Color Computer models shipped with Color BASIC, an implementation of Microsoft BASIC, in ROM. Variants of the OS-9 multitasking operating system were available from third parties. History Tandy Corporation announced the TRS-80 Color Computer in July 1980 to compete with the inexpensive and popular VIC-20. The Color Computer is a completely different design than the Zilog Z80-based TRS-80 models. BYTE wrote, "The only similarity between [the two computers] is the name". The TRS-80 Color Computer derives from an "experimental videotext project by the Kentucky Cooperative Extension Service and the University of Kentucky College of Agriculture" in 1977. Motorola Semiconductor of Austin, Texas, won the contract for the user terminals and Tandy's Computer Division joined later to manufacture the terminals. The initial goal of this project, called "Green Thumb", was to create a low cost Videotex terminal for farmers, ranchers, and others in the agricultural industry. This terminal would connect to a phone line and an ordinary color television and allow the user access to near-real-time information useful to their day-to-day operations on the farm. Motorola's MC6847 Video Display Generator (VDG) chip was released about the time the joint venture started. The 1978 prototype "Green Thumb" terminal used the MC6847 and the Motorola 6809 microprocessor. However, the prototype contained too many chips to be commercially viable. Motorola responded by integrating the functions of many smaller chips into one chip: the MC6883 Synchronous Address Multiplexer (SAM). The SAM, VDG, and 6809 were used as the core of the AgVision terminal. It was also sold through Radio Shack stores as the VideoTex terminal