In 1999, an up-and-coming software engineer in Switzerland was preparing for a conference in France when he learned that the Swiss computer scientist Niklaus Wirth, a pioneer in the field, was also attending and would be on the same flight.
The engineer, Kent Beck, had never met Dr. Wirth. But, he recalled in an interview, upon arriving at the airport he told the gate agent: “My colleague Professor Wirth and I are flying together. Would it be possible for us to sit together?”
Mr. Beck, who would eventually become a well-known programmer in his own right, said that sitting next to Dr. Wirth and talking shop was comparable to a young singer getting the chance to perform with Taylor Swift. Among other feats in computer history, Dr. Wirth had created Pascal, an influential programming language in the early days of personal computing.
“It was out of character for me to be that bold,” Mr. Beck said of his duplicity, “but I would have regretted it the rest of my life.”
The agent assigned him the middle seat next to his supposed colleague, who had the window. Sitting down, Mr. Beck confessed to the fraud right away. Dr. Wirth was mildly amused. “Once a geek knows that you’re interested in what they geek about,” Mr. Beck said, “then the conversation is off and running.”
Dr. Wirth died of heart failure on Jan. 1 at his home in Zurich, his daughter Tina Wirth said. He was 89.
He wasn’t nearly as well known as programmers such as Steve Wozniak, who founded Apple with Steve Jobs, or Bill Gates, who founded Microsoft with Paul Allen. But to Mr. Beck and legions of computer scientists Dr. Wirth was one of the most influential and inspiring scientists of the early computer age.
In 1970, while teaching at the Swiss university ETH Zurich, Dr. Wirth released Pascal, the programming language that powered early Apple computers and initial versions of applications like Skype and Adobe Photoshop. He also built one of the first personal computers and was instrumental in helping a Swiss start-up commercialize the mouse. (The start-up, Logitech, became one of the world’s largest makers of computer accessories.)
The Association for Computing Machinery honored Dr. Wirth in 1984 with the Turing Award, often referred to as the Nobel Prize of computing. Other recipients have included Tim Berners-Lee, the inventor of the World Wide Web, and Vinton G. Cerf, who wrote the code that powers communication on the internet.
For Dr. Wirth, simplicity was paramount in computing, and he created Pascal — named after Blaise Pascal, the 17th-century French mathematician and calculator inventor — as a simpler alternative to languages like BASIC, which he deemed too cumbersome.
BASIC forced programmers to “jump all over the place, writing spaghetti code,” Philippe Kahn, a former student of Dr. Wirth’s who later founded several tech companies, told the New York Times reporter Steve Lohr in an interview for his book “Go To” (2001), a history of software.
“Pascal forced people to think clearly about things and in terms of data structures,” Mr. Kahn said. He added: “Wirth’s influence is extremely deep because so many of the people who were taught in real computer science programs learned Pascal. It was the language of classical thinking in computing.”
Dr. Wirth evangelized for simplicity in a seminal essay for Computer magazine in 1995. “Increasingly, people seem to misinterpret complexity as sophistication,” he wrote, “which is baffling — the incomprehensible should cause suspicion rather than admiration.”
Niklaus Emil Wirth was born on Feb. 15, 1934, in Winterthur, Switzerland, the only child of Walter Wirth, a geography professor, and Hedwick (Keller) Wirth, who managed the family’s home.
He was a precocious child.
“In primary school, I first wanted to become a steam-engine driver, later a pilot,” he recalled in a 2014 interview. “I never aspired to become a scientist, but rather an engineer who understands nature and does something useful with this knowledge.”
He installed a chemistry lab in the family basement. He tinkered with radios. And he built (and crashed) remote-control helicopters. Fixing them taught him an early lesson about simplicity.
“If you have to pay out of your own pocket money,” he told BusinessWeek in 1990, “you learn not to make the fixes overly complicated.”
Dr. Wirth studied electrical engineering at ETH Zurich, a science and technology university. After graduating in 1959, he received his master’s degree from Laval University in Quebec and his Ph.D. in programming languages from the University of California, Berkeley. He taught in Stanford’s newly formed computer science department from 1963 to 1967 and then returned to Switzerland.
At the request of ETH officials, Dr. Wirth started a computer science department. When he tried to identify which programming language he would teach, he found the options too complex. He began working on Pascal, and in 1971 he used it to teach an introductory programming course.
Dr. Wirth made no attempts to monetize Pascal. In fact, he sent the source code on nine-track tapes to anyone who wanted it. This act of collegial generosity coincided with microprocessor revolution, so that professors, budding programmers and emerging computer companies had a free, easy-to-use language to utilize.
“Pascal,” Dr. Wirth liked to say, “was a public good.”
In 1976, Dr. Wirth went on sabbatical to work at Xerox’s Palo Alto Research Center, which had created Alto, one of the first desktop computers with a graphical interface controlled by a mouse.
“I was given an Alto computer for myself alone, on my desk, and that was an absolute change in the way computers were used,” Dr. Wirth recalled in Computer magazine in 2012.
Dr. Wirth coveted an Alto, but they weren’t for sale. So when he returned to Switzerland, he built a similar computer for himself, with its own new programming language.
His first marriage, to Nani Jucker in 1959, ended in divorce. In 1984, he married Diana (Pschorr) Blessing. She died in 2009.
In addition to his daughter Tina, from his first marriage, Dr. Wirth is survived by two other children from that marriage, Chris Wirth and Carolyn Wiskemann; six grandchildren; five great-grandchildren; and his partner since 2017, Rosmarie Müller.
Accepting his Turing Award, Dr. Wirth spoke with awe of the first time he experienced the power of personal computing at Xerox.
“Instead of sharing a large monolithic computer with many others and fighting for a share via a wire with a 3 kHz bandwidth, I now used my own computer placed under my desk over a 15 MHz channel,” he said. “The influence of a 5,000-fold increase in anything is not foreseeable; it is overwhelming.”
Instead of him working for the computer, the computer now worked for him.
“For the first time,” he said, “I did my daily correspondence and report writing with the aid of a computer, instead of planning new languages, compilers and programs for others to use.”