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@symbolics @screwtape @remilia @notptr

RIght, there's no kernel. Everything runs in the same address space. It relies on hardware type-checking to make this *somewhat* safe; mostly you'd enter the debugger instead of crashing. (Or entering the cold load stream, which is more serious but still recoverable.)

Any function could be altered and recompiled directly to memory, not touching the file system. The next call to that function uses the new version. (This applies to recursion as well: if you're many stack frames deep into recursive calls, the active call will "return" into the new function!)

This is *very* useful for debugging user programs.

On the other hand, altering running system code is sometimes... highly inadvisable.

There were no guard rails telling you not to do that. There was no security model worth the mention, by today's standards (just the barest of user id and password at login).

Switching to another world load ("band" in CADR terminology because there used to be some effort to lay them out on a disk in a contiguous band) is rebooting.