An interrupt is a signal from a software program, hardware device or internal clock to the CPU.
It suspends execution of of the running program or processes. A scheduler is used to make the execution
of programs as efficient as possible. There are many ways they could work. Firstly, round robin gives
each process a set amount of 'time slice'. This means that each program is given a turn on the processor.
First some first serve works by processing each program as they arrive, fully before moving onto the next program.
Shortest job first, processes jobs by their length, which means intially a lot of programs are quickly executed,
but fall off later quickly as larger programs are handled.
This is different from shortest remaining time, which instead orders by time to completion.