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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Filesystems: read and write via mmap? (22.05.2012)

Just a note to myself: While reading a blog posting about improved file I/O performance via memory mapped files, I wondered whether it might make sense to write an mmap() implementation first and then create open, lseek, read and write as functions which use an mmap()ped file. Every read() or write() would just turn into a memcpy(), an lseek() would just set an offset variable associated with an mmap()ped file. Plus, the code for transfering disk blocks to memory is likely to be similar to the code needed for paging in a page that was written to disk.

There would be a problem with large files, obviously, because a mapping cannot be larger than the address space.

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