Käivitusjärjestus

Käivitusjärjestus refers to the sequence of operations a computer system performs from the moment it is powered on until it becomes fully operational. This process is crucial for initializing hardware components, loading the operating system, and making the system ready for user interaction.

The käivitusjärjestus typically begins with the Power-On Self-Test (POST), a diagnostic program that checks the integrity of essential hardware such as the CPU, RAM, and graphics card. Upon successful POST, the system's firmware, often a BIOS or UEFI, takes over. This firmware identifies bootable devices, such as hard drives, SSDs, or USB drives, based on a predefined boot order.

Once a bootable device is found, the firmware loads the bootloader from that device into memory. The bootloader is a small program responsible for locating and loading the operating system kernel. The kernel is the core of the operating system and manages system resources. After the kernel is loaded, it initializes various system services, drivers, and the user interface. This complex sequence ensures that all necessary software and hardware components are ready before the user can log in and start using the computer. Errors at any stage of the käivitusjärjestus can prevent the system from booting correctly, often resulting in error messages or a frozen screen.