When you turn on a computer, how does it work? If you suspected that black magic was the cause, then you were on the right track. There is an operating system (OS), a software program that quietly incants the daemons in the background so that the software continues to run without your direct control. Damned to the seventh circle of hell in Dante’s Inferno, they run around responding to network requests, hardware activity, or other programs by performing some task, never seizing to toil until you shut off the computer.
An operating system should be expected to do the following:
- control the hardware, software, peripheral devices (e.g. printers, storage devices)
- support efficient time-sharing, by scheduling multiple tasks to execute during the same interval
- be the intermediary between input and output, and allocate memory to each program so that there is no conflict among the memory of any programs running at the same time
- prevent the user from damaging the system. For instance, prevent user programs from overwriting the operating system or another program’s memory. (You can still design your own operating system if you want. For example, to support a simple single-board computer powered by a 6502 microprocessor. But it is probably quite difficult.)
The operating system loads, or boots, when the computer system is turned on and is intended to run as long as the computer is running. Examples of operating systems are macOS for Apple’s Mac family of computers, Microsoft Windows, Unix, and Linux.
Windows has evolved from a single-user, single-task DOS operating system to the multiuser, multitasking, universal app enabling Windows 10. Unix and Linux were designed from the beginning to be multiuser, multitasking operating systems.