Etukäynnistys

Etukäynnistys, known in English as bootrom or boot ROM, is a small, immutable piece of computer memory containing the initial program that a computer executes when it is powered on or reset. This program, also referred to as firmware, is typically stored in a read-only memory (ROM) chip or a similar non-volatile memory technology, making it permanent and unalterable during normal operation. The primary function of the etukäynnistys is to perform a Power-On Self-Test (POST) to verify that essential hardware components such as the CPU, memory, and basic input/output devices are functioning correctly.

Following the successful completion of the POST, the etukäynnistys is responsible for locating and loading the operating system from a storage device, such as a hard drive or SSD, into the main memory (RAM). It achieves this by following a predefined boot sequence, which dictates the order in which it searches for bootable media. This sequence can often be configured by the user through the system's BIOS or UEFI settings. The etukäynnistys acts as the bridge between the hardware and the operating system, ensuring that the system is ready to accept commands and run applications. In modern systems, the role of etukäynnistys is often handled by Unified Extensible Firmware Interface (UEFI) or the older Basic Input/Output System (BIOS).