In multi$-$core CPU systems, several CPUs $($or cores$)$ can access a common memory space through a shared bus or crossbar switch. In such multi$-$core CPU systems, multiple threads are created to run concurrently in different cores. Interestingly, multiple threads can also be created in a single CPU system. However, the mechanism of running the multiple threads in a single CPU system is slightly different compared to using multi$-$ core CPU systems. Explain how a single CPU system supports running multiple threads