The Implementation of the ULIX Literate Operating System








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A diary documenting the implementation of ULIX-i386

Welcome to the ULIX blog.

Ulix (Literate Unix) is a Unix-like operating system developed at University of Erlangen-Nürnberg. I use D. E. Knuth's concept of Literate Programming for the implementation and documentation. The goal was a fully working system which can be used in operating system courses to show students how OS concepts (such as paging and scheduling) can be implemented. Literate programs are very accessible because they can be read like a book; the order of presentation is not enforced by program logic or compiler restrictions, but instead is guided by the implementer's creative process.

Ulix is written in C and assembler for the Intel architecture. The literate programming part is handled by noweb.

On this page I document my progress with the implementation.

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v0.04: Memory Allocation: Get Frame, Get Page, Update Page Tables (17.08.2011)

OK, the memory system is slowly becoming useful. There's now a bitmap that keeps track of used/free frames in RAM, and there's a function which requests a new page (first getting a frame, then updating the page table and eventually creating a new page table when the old one is full). Next up is some kind of kmalloc()...
Some other things I found out: It's sometimes helpful to use the graphical debug frontend of Bochs. And: There's a free (LGPL-licensed), simple printf() implementation (Georges Menie, 2002) which does not depend on the existence of any libraries: all it needs is a way to put a single character on the console (and I have a putch() already).

Resources used:
printf, by Georges Menie, http://www.menie.org/georges/embedded/

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