Dennis Ritchie: The shoulders Steve Jobs stood on

Dennis Ritchie stands over Ken Thompson as he works on the PDP-11 in 1972.

Story highlights

  • Dennis Ritchie is the father of the C programming language
  • Ritchie used C to build UNIX, the OS that so much is built on
  • "We're all standing on Dennis' shoulders," expert says
And then some.
From B to C
Dennis Ritchie built C because he and Ken Thompson needed a better way to build UNIX. The original UNIX kernel was written in assembly language, but they soon decided they needed a "higher level" language, something that would give them more control over all the data that spanned the OS. Around 1970, they tried building a second version with Fortran, but this didn't quite cut it, and Ritchie proposed a new language based on a Thompson creation known as B.
Depending on which legend you believe, B was named either for Thompson's wife Bonnie or BCPL, a language developed at Cambridge in the mid-60s. Whatever the case, B begat C.
B was an interpreted language -- meaning it was executed by an intermediate piece of software running atop a CPU -- but C was a compiled language. It was translated into machine code, and then directly executed on the CPU. But in those days, C was considered a high-level language. It would give Ritchie and Thompson the flexibility they needed, but at the same time, it would be fast.
That first version of the language wasn't all that different from C as we know it today -- though it was a tad simpler. It offered full data structures and "types" for defining variables, and this is what Richie and Thompson used to build their new UNIX kernel. "They built C to write a program," says Pike, who would join Bell Labs 10 years later. "And the program they wanted to write was the UNIX kernel."
Ritchie's running joke was that C had "the power of assembly language and the convenience of ... assembly language." In other words, he acknowledged that C was a less-than-gorgeous creation that still ran very close to the hardware. Today, it's considered a low-level language, not high. But Ritchie's joke didn't quite do justice to the new language. In offering true data structures, it operated at a level that was just high enough.
"When you're writing a large program -- and that's what UNIX was -- you have to manage the interactions between all sorts of different components: all the users, the file system, the disks, the program execution, and in order to manage that effectively, you need to have a good representation of the information you're working with. That's what we call data structures," Pike says.
"To write a kernel without a data structure and have it be as consist and graceful as UNIX would have been a much, much harder challenge. They needed a way to group all that data together, and they didn't have that with Fortran."
At the time, it was an unusual way to write an operating system, and this is what allowed Ritchie and Thompson to eventually imagine porting the OS to other platforms, which they did in the late 70s. "That opened the floodgates for UNIX running everywhere," Pike says. "It was all made possible by C."
Apple, Microsoft and beyond
At the same time, C forged its own way in the world, moving from Bell Labs to the world's universities and to Microsoft, the breakout software company of the 1980s. "The development of the C programming language was a huge step forward and was the right middle ground ... C struck exactly the right balance, to let you write at a high level and be much more productive, but when you needed to, you could control exactly what happened," says Bill Dally, chief scientist of NVIDIA and Bell Professor of Engineering at Stanford. "[It] set the tone for the way that programming was done for several decades."
The revolution began in 1973, when Ritchie published his research paper on the language, and five years later, he and colleague Brian Kernighan released the definitive C book: The C Programming Language. Kernighan had written the early tutorials for the language, and at some point, he "twisted Dennis' arm" into writing a book with him.
Pike read the book while still an undergraduate at the University of Toronto, picking it up one afternoon while heading home for a sick day. "That reference manual is a model of clarity and readability compared to latter manuals. It is justifiably a classic," he says. "I read it while sick in bed, and it made me forget that I was sick."
Like many university students, Pike had already started using the language. It had spread across college campuses because Bell Labs started giving away the UNIX source code. Among so many other things, the operating system gave rise to the modern open source movement. Pike isn't overstating it when says the influence of Ritchie's work can't be overstated, and though Ritchie received the Turing Award in 1983 and the National Medal of Technology in 1998, he still hasn't gotten his due.
As Kernighan and Pike describe him, Ritchie was an unusually private person. "I worked across the hall from him for more than 20 years, and yet I feel like a don't knew him all that well," Pike says. But this doesn't quite explain his low profile. Steve Jobs was a private person, but his insistence on privacy only fueled the cult of personality that surrounded him.
Ritchie lived in a very different time and worked in a very different environment than someone like Jobs. It only makes sense that he wouldn't get his due. But those who matter understand the mark he left. "There's that line from Newton about standing on the shoulders of giants," says Kernighan. "We're all standing on Dennis' shoulders."