What is the Power-On Self-Test (POST) responsible for?

The Power-On Self-Test (POST) is a critical diagnostic process that occurs when a computer is first powered on. Its main responsibility is to verify that all the essential components necessary for the system to start up properly are present and functioning correctly. During this procedure, the POST checks various hardware components, such as the processor, memory (RAM), storage devices, and other vital hardware parts. If POST detects any issues, it will typically signal an error, often through beep codes or on-screen messages, indicating what may be wrong.

The other options do not accurately represent the function of POST. Loading applications is a task performed by the operating system after the hardware has passed its initial checks. Updating the operating system is a separate process that occurs once the system is fully booted and operational. Cleaning system caches is also unrelated to POST, as it's a maintenance task performed on a running system rather than during the startup sequence.