käynnistyslohkon

A käynnistyslohko, often translated as boot block or boot sector, is a small section of storage, typically at the beginning of a disk or memory device, that contains essential code and data required to start a computer system. Its primary function is to load the operating system or another bootable program into main memory and transfer control to it.

Historically, the boot block was located on floppy disks and hard drives. When a computer powered on, the firmware would read the boot block from the designated boot device. This code would then initiate the loading process, often by reading further parts of the operating system from disk. The Master Boot Record (MBR) on older systems and the GUID Partition Table (GPT) on modern UEFI systems serve as analogous concepts, containing boot loader information.

The size of a boot block is usually very small, often measured in sectors. Despite its size, it plays a critical role in the boot sequence. Modern systems have largely replaced the traditional boot block with more sophisticated boot loaders managed by UEFI firmware. However, the fundamental concept of a small, initial code segment responsible for launching the main system software remains relevant. Understanding the boot block is key to comprehending how computers initiate their operational state.