...ws it. See also: Why doesn't Linux use the hardware context switch via the TSS? How do programs and operating systems transition between rings? when the CPU is turned on, it starts running the initial program in ring 0 (well kind of, but it is a good approximation). You can think this initial p...

...loppy" disks - here's an x86_32 version written in assembler using the old TSS descriptors that can actually run multi-threaded C code (github.com/duanev/oz-x86-32-asm-003) but there is no standard library support. Quite a bit more than you asked for but it can maybe answer some of those lingering ...