You are not expected to understand this - Arun Thomas on Unix Process Switching

"You are not expected to understand this." That is the now famous comment in UNIX v6's process switching (swtch) code. Process switching -- and multitasking more generally -- is a neat magic trick the OS pulls off. It's a delicate dance between the operating system and the hardware. We will dig into how this dance works on UNIX v6 and the PDP11, including the famous comment. We will also look into how the process switching magic happens on a more recent OS and CPU architecture (FreeBSD on x86). It should be a fun trip down the rabbit hole of operating system kernels internals and instruction set specifications