Xinu – A small, elegant operating system

I browsed the source code a bit. Some interesting finds: * The code is pretty simple and clean, clearly for educational purpose. * There's no memory protection. All processes share the same memory space, along with the kernel. * No virtual memory, nor page table. * No notion of ring protection. The kernel and the processes run in the same ring. * Max number of processes is 8. The process table is a fixed size array, of 8 entries. *…

More important than the acronym is the effort itself. XINU is a really interesting project and probably the second OS I was introduced to outside of the POSIXy neighbourhood. It differs from a lot of other projects in that its goals (to my understanding) were very different to the usual approach toward providing POSIX compliance or a platform intended to support layering POSIX on top of a base architecture. I picked up an old copy of the textbook and never…

I own volumes 1, 2 and the PC version. I can vouch for the quality and understandability of the code. I've read a number of operating systems books, and I've found volume 1 to be one of the most straightforward - if you can get past the fact it's written with the PDP-11 in mind. I bought the PC version on a whim after reading volume 1, and found it to be lacking in a number of ways, using BIOS…

I took the course at Purdue that built on Xinu (CS 354, Operating Systems) — Xinu is really just used for teaching purposes. Doug Comer (the creator of Xinu) was my favorite professor — it was inspiring to hear from someone who was pretty close to the development of the Internet and TCP/IP in the 70s (https://en.wikipedia.org/wiki/Douglas_Comer).