Lawrence Tesler, a pioneering computer scientist who helped make it easier for users to interact with computers, whether cutting and pasting text or selecting text by dragging a cursor through it, died on Sunday at his home in Portola Valley, Calif. He was 74.
The cause was not known, his wife, Colleen Barton, said, but in recent years he had suffered the effects of an earlier bicycle accident.
Mr. Tesler worked at a number of Silicon Valley’s most important companies, including Apple under Steve Jobs. But it was as a young researcher for Xerox at its Palo Alto Research Center in the 1970s that he did his most significant work: helping to develop today’s style of computer interaction based on a graphical desktop metaphor and a mouse.
Early in his Xerox career (he began there in 1973), Mr. Tesler and another researcher, Tim Mott, developed a program known as Gypsy, which did away with the restrictive modes that had made text editing complicated. For example, until Gypsy, most text-editing software had one mode for entering text and another for editing it.
Mr. Tesler was passionate about simplifying interaction with computers. At Apple he was responsible for the idea that a computer mouse should have only one button. For many years the license plate on his car read, “NO MODES.”
His first breakthrough at Xerox PARC came when he took a newly hired secretary, sat her in front of a blank computer monitor and took notes while she described how she would prefer to compose documents with a computer. She proceeded to describe a very simple system, which Mr. Tesler then implemented with Mr. Mott.
The Gypsy program offered such innovations as the “cut and paste” analogy for moving blocks of text and the ability to select text by dragging the cursor through it while holding down a mouse button. It also shared with an earlier Xerox editor, Bravo, what became known as “what you see is what you get” printing (or WYSIWYG), a phrase Mr. Tesler used to describe a computer display that mirrored printed output.
And Gypsy brought to fruition the idea of opening a computer file by simply clicking on a screen icon while pointing at it with the mouse cursor. Before that, files had to be opened by typing the file name into a command line.
“At Xerox he pushed a lot for things to be simpler in ways that would broaden the base of users,” said David Liddle, a veteran Silicon Valley venture capitalist who worked with Mr. Tesler at Xerox PARC. “He was always quite focused on users who weren’t also Ph.D.s in computer science.”
Mr. Tesler later joined a small team of researchers run by Alan Kay, a visionary computer scientist who had pioneered the idea of a so-called Dynabook, which would become the inspiration for today’s laptop computers. The group was developing a software environment called Smalltalk, and Mr. Tesler developed a system for searching for software components, which he named the browser.
“He can be hailed as one of the true pioneers of many important aspects of personal computing,” Mr. Kay said.
After attending a demonstration of the Altair, an early hobbyist personal computer, at a Palo Alto hotel in 1975, Mr. Tesler returned to PARC to alert his colleagues to the arrival of low-cost systems. His warnings were largely ignored.
He continued to press for less costly computers. In 1978, with Adele Goldberg and Douglas Fairbairn, he designed a portable machine called NoteTaker, a forerunner of luggable computers like the Osborne, Kaypro and Compaq machines of the early 1980s. But Xerox declined to commercialize the NoteTaker; only a few prototypes were made.
It was Mr. Tesler who gave Mr. Jobs the celebrated demonstration of the Xerox Alto computer and the Smalltalk software system that would come to influence the design of Apple’s Lisa personal computer and then its Macintosh.
Mr. Tesler left Xerox to work for Mr. Jobs at Apple in 1980.
“The questions the Apple people were asking totally blew me away,” Mr. Tesler was quoted as saying in a profile that appeared in IEEE Spectrum, the magazine of the Institute of Electrical and Electronics Engineers, in 2005. “They were the kind of questions Xerox executives should have been asking but didn’t.”
In addition to helping develop the Lisa and Macintosh, Mr. Tesler founded and ran Apple’s Advanced Technology Group, after which he led the design of the Newton hand-held computer, although that proved unsuccessful. The group also created much of the technology that would become the Wi-Fi wireless standard, and Mr. Tesler led an Apple joint venture with two other companies that created Acorn RISC Machine, a partnership intended to provide a microprocessor for the Newton.
Although Apple eventually sold off its holdings in that venture, it would come to dominate the market for the chips that power today’s smartphones. The chip architecture created by the partnership is today the most widely used microprocessor design in the world.
Mr. Tesler left Apple in 1997 for a start-up and later went on to work for both Amazon and Yahoo. He left Yahoo in 2008 and spent a year as a product fellow at 23andMe, the genetics information company. He was most recently an independent consultant.
Lawrence Gordon Tesler was born in the Bronx on April 24, 1945, to Isidore and Muriel (Krechman) Tesler. His father was an anesthesiologist.
In 1960, while attending the Bronx High School of Science, Mr. Tesler developed a new method of generating prime numbers. He showed it to one of his teachers, who was impressed. As Mr. Tesler later recalled, he told the teacher that the method was a formula; the teacher responded, “No, it’s not really a formula, it’s an algorithm, and it can be implemented on a computer.”
“Where do you find a computer?” Mr. Tesler asked.
The teacher said he would first get him a programming manual and then figure out where to find a computer.
One day Mr. Tesler was sitting in the school cafeteria reading his manual, which offered instructions on how to program an IBM 650 mainframe in the most low-level, arcane machine programming language.
A student walked up to Mr. Tesler and asked, “What are you doing with that?”
“I’m learning about programming,” Mr. Tesler responded.
The other student alerted Mr. Tesler to a program at Columbia University, which gave high school students programming time. He was able to use a university computer for a half-hour each week, teaching himself to program before he got to college.
He attended Stanford, graduating in 1965 with a degree in mathematics. While there, he became involved in a number of early projects that prefigured personal computing.
Mr. Tesler had early access to a computer known as a LINC when he worked as a student programmer for the Nobel laureate Joshua Lederberg. The LINC, designed by the M.I.T. physicist Wesley A. Clark, is believed by many computer historians to have been the first true personal computer.
Mr. Tesler’s first start-up venture was a programming consulting company located in a shopping mall next to the Stanford campus. He also used a mainframe computer to build a system to permit the student rooting section at Stanford football games to program elaborate card stunts. It was, Mr. Kay said, a forerunner to the ways in which modern graphical displays would be programmed.
In 1969, with two other scientists at the Stanford Artificial Intelligence Laboratory, Mr. Tesler designed a small computer and proposed the idea behind it to the calculator company Frieden. Although intrigued, the company declined to pursue the idea.
Mr. Tesler left computing for a short while after that and moved to an Oregon commune with his daughter from a short-lived marriage. Lack of work led him back to the Bay Area, where he would join Xerox PARC.
In addition to Ms. Barton, a geophysicist, and his daughter, Lisa Tesler, he is survived by two brothers, Charles and Alan.
At Stanford and afterward, Mr. Tesler was active in both the antiwar movement and the 1960s counterculture. He participated in an alternative school, the Mid-Peninsula Free University, where he taught classes, including one exclusively for people born under the sign of Taurus. In 1968 he taught a class titled “How to End the IBM Monopoly.”
Years later, as a computer scientist at Xerox, he remembered his activist roots, his former colleague Ms. Goldberg said. The Central Intelligence Agency was a Xerox customer, and when agency employees arrived for a meeting, Mr. Tesler attended wearing a trench coat and a fedora.