Käynnistymisprosessin

Käynnistymisprosessi, known in English as the boot process, refers to the sequence of operations that a computer performs when it is powered on to load and initialize the operating system. This process begins the moment the power button is pressed.

Initially, the system's firmware, typically the BIOS or UEFI, performs a Power-On Self-Test (POST). This self-diagnostic checks essential hardware components like the CPU, memory, and graphics card to ensure they are functioning correctly. If POST detects any critical errors, the system will usually halt and indicate the problem, often through beep codes or on-screen messages.

Following a successful POST, the firmware locates the boot device, which is usually a hard drive, solid-state drive, or USB drive, where the operating system is stored. The firmware then loads the bootloader from a designated sector on this device into the computer's random-access memory (RAM). The bootloader is a small program responsible for loading the main operating system kernel.

Once the bootloader is active, it initiates the loading of the operating system kernel. The kernel is the core of the operating system and manages the system's resources. As the kernel loads, it initializes various hardware drivers, sets up memory management, and starts essential system processes and services. The final stages involve loading the user interface and making the computer ready for user interaction. This entire sequence is crucial for bringing the computer from an off state to an operational state.