After AT&T withdrew from the troubled Multics project, Bell Labs researcher Ken Thompson began experimenting on an idle PDP-7 computer, writing a scaled-down operating system with Dennis Ritchie and colleagues. Their work in this period laid the groundwork for Unix, whose design principles—simplicity, portability, and a hierarchical file system—would shape virtually every operating system that followed, including Linux and macOS.
Thompson and Ritchie had grown frustrated after Bell Labs pulled out of the ambitious but bloated Multics project, a joint venture with MIT and General Electric that promised a general-purpose timesharing system but delivered mostly delays. Left without institutional support, Thompson began quietly writing his own minimalist operating system on a PDP-7, a machine so old and unwanted that it had been gathering dust in a corner of the lab.
Working largely alone at first, Thompson wrote an assembler, a rudimentary kernel, and a file system, testing ideas that Multics had complicated with elaborate features. The system's early file-handling and process structure—simple, composable tools that did one thing well—became a philosophy as much as a technical choice, famously distilled later into the Unix maxim of small programs working together through pipes.
By 1970 the project had a name, Unix, a pun on the stripped-down alternative to Multics, and had migrated to a PDP-11. It would go on to influence nearly every subsequent operating system, from BSD to Linux to Apple's macOS, and the C programming language Ritchie created alongside it became the lingua franca of software development for the next half-century.
Key people: Ken Thompson, Dennis Ritchie