Interview Q&A / Operating Systems

1. What are the FCFS, SJF, Round Robin and Priority CPU scheduling algorithms, and how do you calculate waiting time?

   FCFS runs processes in arrival order, SJF picks the shortest job next and gives the lowest average waiting time, Round Robin gives each process a fixed time slice in turn for fair response, and Priority runs the most important process first but can starve low-priority ones unless aging is used.

   IntermediateIn-depth4 min read
2. What is a deadlock and how can you prevent it?

   A deadlock is when two or more processes wait for each other forever, each holding something the other needs. It needs four conditions together; breaking any one of them, for example always taking locks in the same order, prevents it.

   IntermediateIn-depth2 min read
3. What is virtual memory, and how does paging work?

   Virtual memory gives every process its own private address space that looks large and continuous, while the OS maps it onto real RAM in fixed-size blocks called pages (often 4 KB). A page table translates each virtual page to a physical frame, and pages not in RAM can be kept on disk and loaded on demand through a page fault.

   IntermediateIn-depth4 min read