The 539kernel Book: A journey in creating an operating system kernel

Very quickly skimming through the various chapters, it appears that content offers a gentle introduction to the topic. Attention has been made to provide clear and verbose explanations with supportive diagrams.<p>Comparable other &quot;guides&quot; that I have stumbled across is osdev101 [1] and &quot;Writing an operating system from scratch&quot; [2].<p>[1] <a href="https:&#x2F;&#x2F;github.com&#x2F;tuhdo&#x2F;os01&#x2F;blob&#x2F;master&#x2F;Operating_Systems_From_0_to_1.pdf" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;tuhdo&#x2F;os01&#x2F;blob&#x2F;master&#x2F;Operating_Systems_...</a><p>[2] <a href="https:&#x2F;&#x2F;www.cs.bham.ac.uk&#x2F;~exr&#x2F;lectures&#x2F;opsys&#x2F;10_11&#x2F;lectures&#x2F;os-dev.pdf" rel="nofollow">https:&#x2F;&#x2F;www.cs.bham.ac.uk&#x2F;~exr&#x2F;lectures&#x2F;opsys&#x2F;10_11&#x2F;lectures...</a>

I was wondering how this compares with xv6, which is a Unix v6 like 32 bit system written for teaching so peeked at the book and the code. I&#x27;ve only scratched the surface but the developer of the project says that he&#x27;s deliberately written the code in a very simple style to make its function clear and obvious. I&#x27;d agree. It does seem pretty easy to understand. It&#x27;s also very much simpler in structure and the facilities that xv6 in terms of the facilities that it offers. Fun project and it might be a good place those wanting to understand operating systems to start. Here&#x27;s the repo for it.<p><a href="https:&#x2F;&#x2F;github.com&#x2F;MaaSTaaR&#x2F;539kernel" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;MaaSTaaR&#x2F;539kernel</a>

What&#x27;s the significance of 539? Form I-539, &quot;Application to Extend&#x2F;Change Nonimmigrant Status&quot; doesn&#x27;t seem to be a relevant reference.

If I want to porting it to x86_64, except the register width, what else do I mainly need to take care of? Thanks!