When are the built-in commands loaded to memory

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http://unix.stackexchange.com – Let's say if I type in cd in my shell. Is cd loaded from the memory at that moment? My intuition is that these built-in commands are pre-loaded to the system memory after the kernel has been loaded, but someone insisted that they are loaded only when I actually invoke the command (press enter on a shell). Could you please tell me if there is a reference that explains this? (HowTos)