Operating system residence: While a computer is powered on, where must the operating system's kernel and essential components remain resident to manage processes and devices?

Introduction / Context:
The kernel is the core of an operating system, handling CPU scheduling, memory management, and device control. For immediate responsiveness and hardware control, key parts of the OS must remain resident during operation.

Given Data / Assumptions:

• Main storage refers to main memory (RAM).
• Disk drives and removable media are nonvolatile storage, slower and not directly executable by the CPU.
• We consider normal general purpose systems.

Concept / Approach:

After boot, the kernel and some drivers are loaded into RAM. The CPU executes instructions from memory, not directly from disks or floppies. Therefore, the OS core must stay in main storage while the system runs. Additional modules may be loaded on demand, but resident pieces remain in RAM to serve interrupts and system calls promptly.

Step-by-Step Solution:

Verification / Alternative check:

Kernel maps in RAM are visible in system tools, and system crashes result when critical kernel code cannot remain resident, confirming the need for RAM residency.

Why Other Options Are Wrong:

• Floppy disk or disk drive: used for storage and paging, but CPU executes from RAM.
• Primary storage: sometimes used synonymously with main memory, but the item explicitly identifying main storage is the clearest correct choice given the options.
• None of the above: incorrect because main storage is right.

Common Pitfalls:

Confusing where programs are stored long term (disk) with where they execute (RAM). Assuming the entire OS must always be resident; only essential parts must be.

Final Answer:

main storage