Alustusohjelma

Alustusohjelma, often translated as bootloader, is a special type of program that runs when a computer or other device is first turned on. Its primary function is to initialize the hardware and load the operating system or other necessary software into the computer's memory. Without an alustusohjelma, the device would not be able to start up and function.

The alustusohjelma resides in a small, non-volatile memory, such as ROM or flash memory, so it is available even when the main power is off. When the device powers on, the processor begins executing instructions from a predefined memory address, which points to the alustusohjelma. The alustusohjelma then performs a Power-On Self-Test (POST) to check the basic hardware components. After a successful POST, it locates the storage device containing the operating system, reads the necessary boot sectors, and loads the operating system's kernel into RAM. Finally, it transfers control to the operating system, allowing it to take over and complete the boot process.

Different types of alustusohjelmia exist, depending on the device and its complexity. For example, personal computers typically use BIOS or UEFI, while embedded systems might use simpler, custom-designed bootloaders. The specific tasks performed by an alustusohjelma can vary, but its fundamental role in initiating the startup sequence remains consistent.