The next step up in complexity is multiple users . On a network several users can be using the same computer or even the same program on that computer. This is called time-sharing . If a computer has multiple CPUs , it can do multiprocessing . Rather than a single CPU giving out turns to various programs, the different CPUs can work simultaneously.
Speed increases immensely.
But programs written for different operating systems are fooled into thinking their required operating system is present. Common Operating Systems O riginally the operating system was created by each company that manufactured a processor and motherboard. So each operating system was proprietary , that is, unique to each manufacturer. Not good marketing. This required more standardization in operating systems.