When dealing with monolithic operating systems such as Gaia, where are system calls initiated from to achieve a required system level function?

Question

Options

• AKernel Mode
• BUser Mode
• CSlow Path
• DMedium Path

• A
  3% (1)
• B
  86% (30)
• C
  9% (3)
• D
  3% (1)

Explanation

System calls are initiated from User Mode (B) because application code runs in an unprivileged execution context and must request kernel services through a controlled interface - the system call. When a user-mode program invokes a system call, the CPU transitions into Kernel Mode to execute the privileged operation, then returns control back to user space when done.

Why the distractors are wrong:

• (A) Kernel Mode is where system calls are handled/executed, not where they originate - code already running in kernel mode has direct access to privileged operations and doesn't need to issue a system call.
• (C) Slow Path and (D) Medium Path are not execution privilege rings; in some architectures a "fast path" vs "slow path" distinction exists for system call dispatch efficiency, but neither is a mode from which calls are initiated.

Memory tip: Think of User Mode as the "ground floor" and Kernel Mode as the "locked server room" - your application lives on the ground floor and must ring the bell (system call) to get services from the server room. The request always comes from the ground floor.

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