Coen boots off a CD and mounts itself into RAM as and when parts of it are loaded, but you still need the CD in the computer for it to load stuff not in RAM so

Coen boots off a CD and mounts itself into RAM as and when parts of it are loaded, but you still need the CD in the computer for it to load stuff not in RAM so we have a 2nd CD reader + writer for the material You can tell if you're using a part of the OS that hasn't been used in a session yet because you can hear the CD drive with the OS CD in it physically spin up :)