So this is an "what if" question. It may not happen that often, but I am just curious what happens if it would exactly happen. So in short a computer needs space somewhere to store different thinks before or after an calculation. So you have the cache on the CPU (L1,L2,L3) and then the memory and the last is the HDD/SSD swap folder. So let's say your CPU is full the memory is full then the OS will decide to use the SSD/HDD.
Question: But what will happen when the SSD/HDD is full too?
Where will the OS store it? Is this different in OS'es (like Windows, MAC and linux)? Will the PC/MAC reboot?