Modula-based source code resurfaces after nearly four decades
For the first time, the source code of KSOS, backed by the US Department of Defense in the late 1970s and 1980s, is available to the public in the archives of The Unix Heritage Society (TUHS).TUHS volunteers preserve the historical source code and documentation of the original UNIX – or as much of it as is left. A few days ago, in an email to its mailing list, TUHS founder Warren Toomey announced the addition of KSOS to the collection."KSOS was the US Department of Defense (DoD) Kernelized Secure Operating System (KSOS, formerly called Secure UNIX). KSOS is intended to provide a provably secure operating system for larger minicomputers," he wrote.
Despite its age, KSOS sounds surprisingly modern. It was a Unix-compatible OS, implemented in a type-safe programming language, Modula, rather than C. Modula was the late great Niklaus Wirth's successor to Pascal and, in turn, the forerunner to Modula-2 – which we described when it was added to the GNU Compiler Collection in 2022. KSOS was designed to be formally verifiable, so that it could be trusted for use in highly secure systems. It ran on commodity hardware, and its development was sponsored by the US DOD.
