api boot loader bus error comparison user features comparison computer multitasking (cooperative, preemptive) computer network context switch defragmentation device driver device file disk operating system partition distributed operating system embedded operating system exokernel file attribute fixed-priority preemptive forensic engineering general protection fault hal history hobbyist operating system hybrid inode ipc interrupt journal just enough operating system list live cd live usb loadable kernel module memory paging memory protection microkernel mobile operating system monolithic multikernel multilevel feedback queue network operating system object-oriented operating system pxe process process control block protection ring real-time operating system real-time round-robin rump kernel segmentation fault shell shortest job next supercomputer operating system thread time-sharing timeline unikernel usage share user space and kernel space virtual file system virtual memory virtual tape library vkernel cli user interface