What is synchronization? What are the different synchronization mechanisms?

Synchronization means controlling access to a resource that is available to two or more threads or process. Different synchronization mechanisms are:

- Mutex

- Semaphores

- Monitors

- Condition variables

- Critical regions

- Read/ Write locks

What is the basic difference between pre-emptive and non-pre-emptive scheduling.

Pre-emptive scheduling allows interruption of a process while it is executing and taking the CPU to another process 

while non-pre-emptive scheduling ensures that a process keeps the CPU under control until it has completed execution.