Learn in the textbookThe Role and Basic Functions of an OS
DefinitionAn OS (Operating System) is the basic software (基本ソフトウェア) that manages the hardware and provides common functions to applications.
ExplanationAn application only has to ask the OS to draw the screen or read and write storage, so it does not need its own control logic for each device. Multitasking (マルチタスク), where several programs run side by side, also works because the OS divides up processor time. Right after a PC is switched on, a separate program called BIOS runs to set up the hardware before the OS takes over.
AnalogyIt is a bit like a railway company. It looks after all the tracks and signals, so passengers (apps) just pick a destination, get on, and arrive.
Memory hookTo operate a machine is to run it. The system whose job is running the machine is the Operating System.