First Come First Served (FCFS) scheduling algorithm: It is a non preemptive scheduling algorithm. Here processes are kept in a queue and are executed one by one. Whenever a new process arrives it is kept at the end of the queue. So, this is the last process in the queue. Now, when a new process arrives after this process, the new process becomes the last process in the queue. When a process which is running is blocked the next process in the queue is run and the blocked process (when it is ready) is placed at the end of the queue. FCFS is usually used in batch systems. The advantage of FCFS algorithm is that it is very easy to implement. The disadvantage of FCFS algorithm is that since it is non preemptive, CPU usage can be wasted in some situations.
Round Robin scheduling algorithm: It is a preemptive scheduling algorithm. In this algorithm, every process is considered as equal. A time interval to run known as quantum is assigned to every process. A queue is maintained with quantum for each process. After a process has finished its quantum, it is placed at the end of the queue and a new process is run from the queue. Round Robin scheduling algorithm is used for personal computers and servers.