Concurrency
You may have heard about multitasking – well, concurrency has the same idea. If your system is managing multiple tasks at the same time, you need to understand that it does not necessarily mean that the tasks are being run in parallel. Instead, there can be a task scheduler in the middle; this simply switches very quickly between the different tasks and performs a tiny bit of each of them in a fairly small amount of time.
This certainly happens when you have just one processor unit. For the rest of our discussion in this section, we assume that we are operating on just one processor unit.
If a task scheduler is sufficiently fast and fair, you won't notice the switching between the tasks, and they'll appear to be running in parallel from your perspective. That's the magic of concurrency, and the very reason why it is being used in most of the widely known operating systems, including Linux, macOS, and Microsoft Windows.
Concurrency could...