John Roach, a marketing visionary who helped make the home computer ubiquitous in the late 1970s by introducing the fully assembled Tandy TRS-80 for $599.95 or less through RadioShack chain stores, died on Sunday in Fort Worth. He was 83.

His death, in a hospital, was confirmed by his wife, Jean Roach. No cause was given.

Mr. Roach already had college experience fiddling with refrigerator-size mainframes by 1967, when he joined the Tandy Corporation, a Texas conglomerate that was founded as a leather goods company and included RadioShack and its thousands of franchised dealers in electronics farrago.

He was instrumental in prodding Tandy to venture into the computer market. At the time, most small computers were sold as kits to be assembled by hobbyists, but Mr. Roach believed that consumers would welcome a model that they just needed to plug in.

His team presented the original TRS-80 prototype — cobbled together from a black-and-white RCA monitor, a keyboard and a videocassette recorder — to Tandy’s chief executive, Charles Tandy, and to Lewis Kornfeld, the president of RadioShack, in January 1977.

The Apple 1 had been introduced the year before, and Commodore and other companies were marketing their own home computers, but the TRS-80 (the initials stood for Tandy RadioShack) quickly became, for a time, the most popular computer on the market.

“Charles blew a little smoke and said, ‘Build a thousand and if we can’t sell them, we will use them in the store for something,’” Mr. Roach recalled in remarks to the Fort Worth Executive Round Table last month.

“We were finally able to ship some machines in September and shipped 5,000 that year, all we could assemble,” Mr. Roach said. “Our competitors shipped none.”

At just under $600 (about $2,700 in today’s dollars), the computer was relatively cheap (it was $399 if connected to a separately owned viewing screen). It was available in all 8,000 of the company’s stores.

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