Explain Thread Scheduling with suitable example.

Thread scheduling is a process by which a system determines which thread to run next. This is a key component of any multitasking operating system. Thread scheduling can be either preemptive or non-preemptive.

Preemptive scheduling allows a process to be interrupted in the middle of its execution, taking the CPU away and allocating it to another process. Non-preemptive scheduling, on the other hand, ensures that a process relinquishes control of the CPU only when it finishes with its current execution cycle.

Let's take an example to understand this better:

Suppose we have three threads: T1, T2, and T3, each requiring different CPU time. The operating system could use a simple round-robin scheduling algorithm, where each thread gets a small unit of CPU time, usually from 10-100 milliseconds. After this time has elapsed, the thread is preempted and added to the end of the ready queue.

For example, if each thread gets 20 milliseconds of CPU time, the scheduler will start with T1. After 20 milliseconds, T1 is preempted and T2 starts execution. Again, after 20 milliseconds, T2 is preempted and T3 starts execution. This process continues in a cyclic way.

This way, the operating system ensures all running threads are given CPU time, and it appears to the users that all threads are executing simultaneously, which is the main goal of multitasking operating systems.