Adam Osborne, a British technical writer who became one of Silicon Valley's legends by introducing the first portable personal computer in 1981, died on March 18 in Kodiakanal, India. He was 64 and had a series of strokes in the last decade, said his former wife Cynthia Geddes.

The Osborne 1 computer, which was introduced at the West Coast Computer Faire in June 1981, was a 24-pound luggable machine that came with a large library of essential software, including a word processor, spreadsheet, database and programming languages. At the time, it was a startling innovation in an industry that was dominated by a do-it-yourself hobbyist culture.

Dr. Osborne distinguished the Osborne Computer by noting that it was ''adequate,'' a break with the superlative-filled industry promotion of the era.

''I liken myself to Henry Ford and the auto industry,'' he said in a 1982 interview. ''I give you 90 percent of what most people need.''

The machine created a sensation in the rapidly growing PC marketplace, even though it came with a cramped five-inch display screen. The common belief at the time was that customers were paying for the software, which included popular programs like WordStar, the SuperCalc spreadsheet and Bill Gates's version of the Basic programming language and were getting the computer free.

The Osborne Computer Corporation in Hayward, Calif., became synonymous with the Silicon Valley tradition of hypergrowth defined by companies like Apple Computer and Atari. Orders for the Osborne 1 totaled 8,000 in 1981 and jumped to 110,000 in 1982. At one point, the company said that it had a 25-month backlog of orders.

In 1982, Dr. Osborne, who was an enthusiastic pitchman with a stylish British accent, prematurely announced the second-generation Osborne, called the Executive.

When the company encountered manufacturing difficulties, it found itself drowning in inventory as customers deferred purchases of the original machine in expectation of the new one.

The computer maker became an iconic symbol of Silicon Valley's boom-and-bust economy on Sept. 13, 1983, when it declared bankruptcy and a local newspaper photographer captured Dr. Osborne covering his face with his briefcase as he headed for his car in the company parking lot.

Although the industry focused on the company's management and logistical problems, at the time Osborne was feeling increasing competition from I.B.M. as well as other makers of portable computers including Kaypro, Corona and Compaq. Several industry experts have said the company's collapse had as much to do with its failure to jump quickly to a 16-bit microprocessor and I.B.M. compatibility.

Dr. Osborne was born in Thailand in 1939 to British parents. He grew up in southern India, where his father, the writer Arthur Osborne, a devotee of Sri Ramana Maharshi, helped popularize ideas from Eastern religion in the West. Dr. Osborne moved to England as a teenager and received a degree in chemical engineering from Birmingham University.

He later received a doctorate in chemical engineering at the University of Delaware and took a job with Shell Oil in California. In the mid-1970's he became a computer hobbyist and began self-publishing on computing.

In 1979, he sold his small publishing company to McGraw-Hill and used the money along with venture capital to found Osborne Computer in 1980.

After Osborne Computer collapsed, he founded Paperback Software International, with the idea of selling inexpensive software bound into books. The company was an initial success, but it ultimately lost a legal battle with Lotus Development in 1987 over a spreadsheet program that infringed the operating commands of Lotus 1-2-3.

He returned to India in 1992 when his health began to fail to live with his sister, Katya.

In addition to his sister and Ms. Geddes, his first wife, he is survived by three children, Alexandra and Paul, both of Oakland, Calif., and Marc of Washington. He was divorced from his second wife, Barbara Zelnick.

Photo: Adam Osborne (Terrence McCarthy, 1987)