The operating system is one type of system software. The operating system is the software that your computer runs on such as windows xp and windows 7 or mac.
yes yes it is because the computer will say missing operating system without it and if the operating system is windows xp it will have a kernel named ntoskrnl.exe
Operating system act like a manager between the system hardware and application software (Such as Firefox) Also they do the fallowing tasks CPU scheduling Memory management Inter-process communication