> When you have enough memory for the set of all elements you want to store but not enough contiguous memory for the set of all elements you want to store That

> When you have enough memory for the set of all elements you want to store but not enough contiguous memory for the set of all elements you want to store That's only relevant if you don't have an MMU tho. So not on any desktop or embedded system where ram is measured in gigabytes. Otherwise it's up to the OS to handle that - only individual memory pages are contiguous, but not sets of pages.