Fernando "Corby" Corbató, a distinguished MIT professor emeritus whose groundbreaking work on time-sharing systems in the 1960s transformed computer accessibility, passed away at his residence in Newburyport, Massachusetts on Friday, July 12. The computing pioneer was 93 years old.
Long before cybersecurity and cloud computing became household terms, Corbató spearheaded the creation of one of the world's earliest operating systems. His revolutionary "Compatible Time-Sharing System" (CTSS) enabled simultaneous computer usage by multiple individuals, dramatically accelerating programming workflows. This innovation is also widely recognized as the first computer system to implement password protection.
Following CTSS, Corbató directed the Multics time-sharing initiative, which directly influenced operating systems like Linux and established numerous foundations for contemporary computing. Multics additionally served as an invaluable training platform for emerging programming talent, including C language creator Dennis Ritchie, Unix developer Ken Thompson, and spreadsheet pioneers Dan Bricklin and Bob Frankston.
Prior to time-sharing technology, computer usage was an arduous process requiring specialized knowledge. Users would prepare programs on punch cards and submit them in batches to operators, who would then process them individually over several hours. Even minor coding errors necessitated repeating this entire procedure, often multiple times.
However, with CTSS's introduction in 1961, responses were delivered in seconds, permanently transforming the programming development model. Decades before the personal computer revolution, Corbató and his team also facilitated user communication through primitive versions of email, instant messaging, and word processing applications.
"Corby ranks among the most influential researchers in making computing accessible to diverse users for multiple purposes," notes long-time collaborator Tom Van Vleck. "He understood that these innovations don't merely enhance efficiency; they fundamentally revolutionize how people interact with information."
Beyond improving computing efficiency, CTSS unintentionally helped establish the very concept of digital privacy. As different users sought to maintain confidential files, CTSS introduced the notion of individual accounts secured by personal passwords. Corbató's vision of democratizing access to high-performance computers also anticipated cloud computing trends, where technology giants like Amazon and Microsoft now provide shared server resources to businesses globally.
"While others had previously suggested time-sharing concepts," explains Jerry Saltzer, who collaborated with Corbató on CTSS after initially serving as his teaching assistant, "his unique contribution was the foresight and determination necessary to transform these ideas into reality."
CTSS also inspired MIT to establish "Project MAC," which later evolved into the Laboratory for Computer Science (LCS). This laboratory eventually merged with the Artificial Intelligence Lab to form MIT's largest research facility, the Computer Science and Artificial Intelligence Laboratory (CSAIL), now housing over 600 researchers.
"It's impossible to overstate how Corby's time-sharing innovations fundamentally transformed computing as we recognize it today," states CSAIL Director Daniela Rus. "From personal computers to smartphones, the digital revolution directly traces its origins to his pioneering work at MIT nearly six decades ago."
In recognition of his extraordinary contributions, Corbató received the Association for Computing Machinery's prestigious Turing Award in 1990, frequently referred to as "the Nobel Prize of computing."
From sonar technology to CTSS innovation
Born in Oakland, California on July 1, 1926, Corbató enlisted as a technician in the U.S. Navy at age 17, where he initially discovered his passion for engineering while working with various radar and sonar systems. Following World War II, he completed his bachelor's degree at Caltech before pursuing a PhD in physics at MIT.
During his doctoral studies, Corbató encountered Professor Philip Morse, who recruited him to join Project Whirlwind, the first computer capable of real-time computation. After completing his PhD, Corbató joined MIT's Computation Center as a research assistant, rapidly advancing to become the center's deputy director.
It was during this period that he began exploring methods to enhance computing efficiency. Despite its innovations, Whirlwind remained a cumbersome machine. Researchers frequently struggled to accomplish substantial work, as they were limited to half-hour time slots on the system. (Corbató noted that the machine tended to crash approximately every 20 minutes.)
Since computer input and output devices operated significantly slower than the computer itself, a multiprogramming approach emerged in the late 1950s, allowing a secondary program to run whenever the primary program awaited device completion. Time-sharing expanded upon this concept, enabling other programs to execute while the initial program waited for human user input, thus facilitating direct user interaction with the first program.
Saltzer emphasizes that Corbató pioneered a programming methodology that contemporary developers would describe as agile design.
"Though it's a buzzword today, back then it was simply this iterative coding approach that Corby championed, which proved remarkably effective," Saltzer observes.
In 1962, Corbató published a paper detailing CTSS that quickly generated excitement within the nascent computer science community. The subsequent year, MIT invited hundreds of programmers to experience the system firsthand, catalyzing intensified research into time-sharing technologies.
Demonstrating remarkable foresight about future technological adoption, Corbató was both astonished and entertained by how rapidly users adapted to CTSS's efficiency.
"Once users experience immediate computer response, delays of even a fraction of a minute become intolerably long," he insightfully wrote in his 1962 paper. "Initial evidence suggests that programmers would enthusiastically embrace such systems if they were widely accessible."
Multics, meanwhile, enhanced CTSS's more improvised design with a hierarchical file system, improved email and instant messaging interfaces, and more sophisticated privacy controls. Peter Neumann, who worked at Bell Labs during their collaboration with MIT on Multics, notes that its architecture prevented numerous vulnerabilities that plague modern systems, such as "buffer overflow" (which occurs when a program attempts to write data beyond the computer's short-term memory limits).
"Multics was decades ahead of the rest of the industry," Neumann asserts. "It was meticulously software-engineered, years before software engineering was even recognized as a distinct discipline."
While leading these time-sharing initiatives, Corbató functioned as a soft-spoken yet determined leader—a methodical thinker who led through example and possessed a distinctly systems-oriented worldview.
"What I appreciated about working for Corby was knowing he could perform my role if necessary," Van Vleck reflects. "His comprehensive understanding of the intricate details of our work inspired profound dedication to Multics, while he consistently treated everyone on the team with exceptional courtesy."
Another enduring contribution from the professor is "Corbató's Law," which posits that the number of code lines a programmer can write daily remains constant regardless of the programming language used. This principle is frequently cited by developers advocating for higher-level programming languages.
Corbató remained actively engaged with the MIT community, serving as associate department head for computer science and engineering from 1974 to 1978 and again from 1983 to 1993. He belonged to the National Academy of Engineering and was a fellow of both the Institute of Electrical and Electronics Engineers and the American Association for the Advancement of Science.
Corbató is survived by his wife, Emily Corbató of Brooklyn, New York; his stepsons, David and Jason Gish; his brother, Charles; his daughters, Carolyn and Nancy, from his marriage to his late wife Isabel; and five grandchildren.
Instead of flowers, contributions may be made to MIT's Fernando Corbató Fellowship Fund through Bonny Kellermann in the Memorial Gifts Office.
CSAIL will host an event commemorating and celebrating Corbató's legacy in the coming months.
