Operating systems 101: An operating system is best described as which of the following?

Introduction / Context:
The operating system (OS) is the foundational software layer that manages hardware and provides services to applications. It is not hardware itself, but rather software that coordinates resources and enforces policies such as scheduling, memory protection, and I/O control.

Given Data / Assumptions:

• The OS abstracts CPU, memory, storage, and devices.
• It exposes APIs and system calls to user programs.
• The question seeks the category that correctly describes an OS.

Concept / Approach:
Operating systems consist of software routines: kernels, drivers, file systems, network stacks, and user-space utilities. These routines orchestrate hardware but are not themselves physical components. The OS interacts with I/O devices, but it is not the devices; it is the controlling software layer.

Step-by-Step Solution:

Verification / Alternative check:
OS textbooks define the OS as system software that manages hardware and provides services; this matches “collection of software routines.”

Why Other Options Are Wrong:
Hardware components and I/O devices are managed by, but are not part of, the OS. “All of the above” incorrectly mixes categories.

Common Pitfalls:
Confusing firmware or embedded control logic with the OS; conflating peripherals with the software stack that controls them.

Final Answer:
A collection of software routines