With infinite resources, for example memory, then many of the things that an operating system has to do would be redundent. One of the basic tricks of any operating system is the ability to make a small amount of physical memory behave like rather more memory. This memory is known as virtual memory. The idea is that the software running in the system is fooled into believing that it is running in a lot of memory. The system divides the memory into easily handled pages and swaps these pages onto a hard disk as the system runs. The software does not notice because of another trick - multi-processing.