ITPEC IP October 2021 Question 20

The OS allocates the CPU, memory and auxiliary storage to application programs — resource management is the OS's central job.

Several programs run on a PC at once, and they all need the same hardware. The OS manages these resources: it gives each task its turn on the CPU, assigns memory areas, manages files on the auxiliary storage and controls input and output devices. Applications call the OS for these services instead of driving the hardware themselves.

Answer (b)

Why not others:

• •(a) — the interface between an OS and applications (its API) differs from one OS to another, so an application is built for a particular OS, such as Windows or macOS
• •(c) — an OS does not automatically convert the character set of files; the application must know or convert the encoding, and text read with the wrong one is garbled
• •(d) — applications use the OS's published interfaces, so no source code is needed; many PC OSs, Windows and macOS among them, are not open source

Key rule: The OS manages hardware resources (CPU, memory, storage, I/O) and offers them to applications through its interface, which is specific to that OS.

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