Protected Mode Gotcha: How Misunderstood Segment Registers Broke AxonOS's Keyboard Handler

For OS developers, this debugging story reveals a fundamental gap: confusing real mode and protected mode segment register behavior is a critical pitfall. Understanding that segment registers in protected mode hold GDT selectors—not physical addresses—is essential for reliable kernel development, and this hands-on case study shows how such misconceptions can easily consume hours of frustration. Whether building a hobby OS or working on production kernels, grasping your CPU's memory model is non-negotiable.