TNB Night Owl – Larry Tesler

Larry Tesler's college friends at a computer console at Stanford University circa 1962-1964. Screen Capture CHI 2011 SIGCHI Lifetime Practice Award: Larry Tesler.

Meet Larry Tesler, a man most people have never heard of yet probably has done more to help people work more efficiently, productively, and safely, than all the politicians on the planet put together.

In high school, Larry excelled at mathematics and thought he would major in that subject in college. That changed in 1960 when his math teacher showed him a mathematical algorithm with which to find prime numbers, and challenged Larry with the suggestion that he program a computer to run the algorithm. Larry started studying IBM 650 machine language, even though he had no access to a computer – all of which were mainframes back in the day. A chance meeting opened the door to the use of an IBM 650 computer at Colombia University.

I ended up getting 30 minutes of computer use every [other] Saturday morning for a few months during the 1960-61 school year. This blissful period lasted until I accidentally broke the drive belt of the magnetic drum memory. The administrator banished me from the facility. But I had become irreversibly hooked on programming.

Larry Tesler

Larry graduated in 1961 from the Bronx High School of Science and began studying computer science, then still a brand new field, at Stanford University. While the experience with the mainframe hooked him on programming, he also found it frustrating. Thus began his life-long philosophy and passionate belief that computers should not only be easy to use, but available to everyone. As a result, he became interested in user-interface design, and the concept of a single-user workstation (which we now know as the personal computer (PC)).

One reason early computers weren’t easy to use is that they were often designed to be operated in different ‘modes’. For example, in one mode, word processor software would allow the user to edit text, while in another mode the user could format the document’s page. The commands in each mode were different, or worse they were the same but did different things. A user could forget which mode they were in, and become confused if the computer did something different than expected. Novice users – or experienced users trying to use an unfamiliar program – could become trapped in a mode, unable to figure out how to get out of it and into another mode. Take WordPerfect, for instance, which was originally developed on a mainframe, for mainframe users. If you used WordPerfect on a PC in the 1980s and 1990s, you may remember what it was like: people either loved it or hated it, depending on how well they could (or couldn’t) remember all the different commands in each mode. Other classic computer programs that used modes include Emacs and vi, which made them hard for the average user to learn.

Larry campaigned tirelessly against the use of modes in user-interface design. In dedication to his cause, he ordered vanity license plates [No Modes], made the name of his website ‘’, and the name on his Twitter account ‘@nomodes’.

Larry’s efforts to rid computers of modes has safety implications that has caught the attention of engineers and designers. A number of major accidents have been attributed to mode confusion by the operators of aircraft and ships, including; Asiana Airlines Flight 214, Air France Flight 447, and the collision between the USS John S. McCain and the Alnic MC, a civilian tanker vessel in the Strait of Malacca in 2017. Larry’s philosophy to eliminate modes, and therefore the mode confusion that can result, has influenced at least some companies to build safer machines by eliminating modes.

Probably the innovation that Larry is most famous for, are the now-ubiquitous ‘cut’, ‘copy’, and ‘paste’, functions found on virtually every device with word processing capability. For that accomplishment alone, he’s an international geek-hero. (Hero-geek?)

He coined the word ‘modeless’, and the phrase, ‘friendly user interface’ (not to be confused with ‘user-friendly’ which is attributable to someone else). Larry was the first to name a piece of software a ‘browser’, with his Smalltalk Browser program (1976) which eventually led to today’s web browsers.

In the 1970s, Larry worked for Xerox at the company’s famous Palo Alto Research Center (PARC) where he continued to champion modeless design. While at PARC, Tesler declared, “What you see on the screen should be what you get when you print it”, which another techie simplified to “WYSIWYG”.

He contributed to the development of the
graphical user interface (GUI) while working at PARC, and later at Apple Computer in the 1980s. The first computer on the market with a GUI was the Apple Lisa, followed just one year later by the Apple Macintosh. Micrsoft Windows came along a few years later. The GUI was a revolutionary idea at a time when the command line interface ruled the industry. We take the GUI for granted today, because it’s everywhere; in our computers, our phones, our cars, and on, and on, and on.

I have been mistakenly identified as “the father of the graphical user interface for the Macintosh”. I was not. However, a paternity test might expose me as one of its many grandparents.

Larry Tesler

He is the author of Tesler’s Law of Conservation of Complexity (1984), and Tesler’s Theorem (1970), which are deep computer science subjects. Larry has made numerous other contributions to computer science in addition to those already mentioned. He was also passionate about sharing what he’d learned and helping others succeed in the tech sector.

There’s almost a rite of passage – after you’ve made some money, you don’t just retire, you spend your time funding other companies. There’s a very strong element of excitement, of being able to share what you’ve learned with the next generation.

Larry Tesler, in an interview with the BBC, 2012

Larry was born April 24, 1945, in the Bronx, New York. He passed away February 16, 2020, at age 74. He was a pioneer and a giant in the field of computer science, an innovator and a rebel that fought the mainframe-centric model of computing, and championed the distributed model which placed each individual user at the center of computing. Larry made the world a better place for technology users in the information age. God bless him, and may he rest in peace.

There are at least a dozen videos on YouTube about Larry. This one features him discussing his role in the industry: “CHI 2011 SIGCHI Lifetime Practice Award: Larry Tesler” (1:11:22). It’s a bit long, but very interesting. (If you’re a true geek, you must love tech history).

Questions of the night: What was your first experience with a computer? Were you at home, in college, or at your workplace? Was it a PC, a mainframe, or a minicomputer?

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About Richard Doud 622 Articles
Learning is a life-long endeavor. Never stop learning. No one is right all the time. No one is wrong all the time. No exceptions to these rules.