Käynnistyslevy

Käynnistyslevy, also known as a boot disk or startup disk, is a storage medium that contains the necessary files and instructions for a computer to start up or boot. Typically, this medium is a floppy disk, CD-ROM, DVD, or USB flash drive, although historically it could also be a hard drive partition. When a computer is powered on, its BIOS or UEFI firmware looks for a bootable device to load the operating system from.

The primary purpose of a käynnistyslevy is to initiate the boot process. This involves loading a bootloader, which is a small program responsible for loading the operating system kernel into memory and starting its execution. Without a bootable device, the computer cannot load its operating system and will usually display an error message or halt.

Käynnistyslevyt are often used for several key functions. They are essential for installing a new operating system onto a computer. They can also be used to troubleshoot operating system problems, recover lost data, or run diagnostic tools when the main operating system is not functioning correctly. In some cases, a käynnistyslevy might contain a minimal operating environment or a specialized utility program. The concept is fundamental to how computers begin their operation and allows for system recovery and maintenance outside of the normal operating system environment.