Why is round robin algorithm considered better than first come first served algorithm?

The first come first served algorithm is the simplest scheduling algorithm known. The processes are assigned to the CPU on the basis of their arrival time in the ready queue. Since, it is non-preemptive once a process is assigned to the CPU, it will run till completion. Since a process takes the CPU till it is executed it is not very good in providing good response times. It can make other important processes wait un-necessarily.

On the other hand, the round robin algorithm works on the concept of time slice or also known as quantum. In this algorithm, every process is given a predefined amount of time to complete the process. In case, a process is not completed in its predefined time then it is assigned to the next process waiting in queue. In this way, a continuous execution of processes is maintained which would not have been possible in case of FCFS algorithm

Explain how a copying garbage collector works. How can it be implemented using semispaces?

The copying garbage collector basically works by going through live objects and copying them into a specific region in the memory. This collector traces through all the live objects one by one. This entire process is performed in a single pass. Any object that is not copied in memory is garbage.

The copying garbage collector can be implemented using semispaces by splitting the heap into two halves. Each half is a contiguous memory region. All the allocations are made from a single half of the heap only. When the specified heap is half full, the collector is immediately invoked and it copies the live objects into the other half of the heap. In this way, the first half of the heap then only contains garbage and eventually is overwritten in the next pass.