Tesler went back to the Stanford AI lab, hoping he could find something to do there that was more "real" than advanced research. The lab manager, Les Earnest, was interested in computer typesetting, a nascent technology at the time, and assigned Tesler to develop a "document compiler," something that could format text and generate footnotes, tables of contents, indexes, and bibliographies.

So in 1971 Tesler wrote a piece of software that would allow users to tuck formatting commands inside normal text as they typed, like inserting a parenthetical expression. When the computer displayed or printed text coded in this manner, it would adjust the text as instructed—boldface or italic, for example—and hide the instruction. This software, called Pub, was one of the first, if not the first, of what would become a "markup language with embedded tags and scripting." The best-known such language today is Dynamic HTML, used in Web design. Pub was distributed through the ARPANet, a precursor to the Internet, and widely used in universities.

Tesler continued to check in with PARC, and at the end of 1971, Xerox offered him a job in the On-Line Office System Group, then building an ambitious distributed operating system for office applications. Tesler was interested in personal computers, so the project didn't thrill him. And he thought the offered pay was too low. So he turned PARC down. Again.

More than a year went by. It was early 1973, and PARC was in the thick of developing what would be the first personal computer, the Alto. It made Tesler yet another job offer, and this time he didn't refuse. He would split his time between the Office System Group and Alan Kay's Learning Research Group.

One goal of the Learning Research Group was to develop Smalltalk, the first dynamic object-oriented programming language—the first language, that is, designed to create programming entities that had characteristics and attributes that could be passed on to other entities. A generic "job" entity, for example, might have such attributes as a salary, a department, and health benefits. Another entity, such as "manager," could be created, automatically inheriting those attributes and gaining additional ones, such as supervisory duties or security clearances. Smalltalk back in the 1970s contained almost all of the concepts in today's enormously popular Java language.

As one of Tesler's first tasks at PARC, he and a co-worker wrote a paper on the future of interactive computing, which for the first time talked about cut-and-paste as a way of moving blocks of text, images, and the like. It also described representing documents and other office objects stored on the computer as tiny images—icons—instead of as a list of names [see photo, "Iconography"].

Today, icons are everywhere—as folders, documents, and the trash can or recycle bin for deleted files. The radicalness of the concepts is apparent only when you understand that, in those days, opening up a document required knowing—and typing in—its exact name and document type.

Before Tesler arrived, the Office System Group had already formulated some ideas about how they expected users to interact with computers. Their concept was based on the three-button mouse and depended heavily on the use of modes. In a mode-based system, you first tell the computer what type of thing you are going to do, and then you do it. So if you want to insert text in a document, you put the computer in insert mode, select your insert point, type in the text, and then exit the insert mode. If you want to delete, you put the computer in delete mode, select the text to be removed, execute the deletion, and exit the mode. It could take weeks or months to become proficient in the use of the system, but at the time, practitioners believed nothing much simpler than that could offer as much power to the user.

"I was aghast," Tesler says. He reasoned that ordinary users wouldn't invest more than a few minutes in learning a user interface and that they would lose track of modes, risking deleting instead of inserting, for example, with potentially disastrous results. But Tesler found few allies among his colleagues, who, incredibly to Tesler, felt that a moded interface was intuitive.

Meanwhile, PARC hired Sylvia Adams, now Sylvia Amundsen, a secretary whose previous high-tech experience had been limited to the IBM Selectric typewriter. When she arrived for her first day of work, Tesler recalls, "I grabbed her. I didn't want her to get contaminated by some word processor that we were using."

He sat her in front of a blank computer screen and gave her a printed page of text that he had marked up with corrections. "See this text?" he asked. "Pretend it's on the screen. And see these proofreading marks? Your job is to make those changes on the screen. How would you do it?"

"Well," she said, "I have to insert something there, so I would point there, and then I would type what I wanted. And to delete this, I would draw through it." Tesler took notes as Adams invented, in effect, the modeless user interface for text editing.

Then Tesler had her use the moded system in use at PARC. She hated it; she got stuck frequently in the wrong mode and had trouble getting out of it. She proved his theory that it was a bad system for a nontechnical beginner.

The test was enough to convince Tesler's boss, Bill English, to allow Tesler to work on an alternative to the moded interface. As he developed it, he continued his user experiments, regularly grabbing "civilians" from the building lobby—delivery people, friends picking up employees for lunch, anybody without computer experience. Tesler sat them down in front of a computer screen now running prototype software and asked them to edit text.

"They were such novices," Tesler recalls. "With one couple, the first thing they said when looking at the crisp text on the screen was, 'You get really good TV reception in here.'"

After writing a simple text editor called Mini Mouse, he went on to develop Gypsy, a modeless text-processing system that was the first to use many now-familiar elements: the cut-and-paste function to move text, a fill-in form to enter search terms, selection of text by holding down a mouse button and dragging the cursor through it, bold and italic type styles, and what-you-see-is-what-you-get printing. Tesler coined that phrase and other now-common terms [see http://www.spectrum.ieee.org for more]. Gypsy also first implemented click-to-open files; previously, the only way to open a file was to type its name and the Open command. Gypsy was never commercialized, but it was used for years to edit manuscripts at Ginn and Co., a textbook publisher then owned by Xerox. Tesler went on to develop other pathbreaking text-formatting software, but none of it made it to market.