System startup: when a computer is powered on or restarted, which special absolute loader is executed to initialize hardware, locate the operating system, and start the boot process?

Introduction / Context:
Right after power-on, a computer cannot rely on an operating system already residing in memory. A minimal program stored in firmware or a predefined location must take control, test hardware, and bring in the operating system. This early-stage program is a specialized, minimal loader.

Given Data / Assumptions:

• Bootstrapping begins from immutable or semi-immutable storage (ROM/flash).
• The program can access devices to fetch the OS loader or kernel.
• Absolute addressing is typically used because the loader is built for a fixed location.

Concept / Approach:
The bootstrap loader initializes essential hardware, identifies a boot device, loads a more capable secondary loader or OS image into RAM, and transfers execution. It acts as a tiny absolute loader, not a general-purpose linker or full dynamic loader.

Step-by-Step Solution:

Verification / Alternative check:
BIOS/UEFI on PCs, boot ROMs on embedded devices, and bootloaders like U-Boot implement these steps and embody the bootstrap concept.

Why Other Options Are Wrong:

Common Pitfalls:
Confusing generic loaders with the minimal, firmware-invoked bootstrap stage; assuming the OS is present in RAM at power-on.

Final Answer:
bootstrap loader.