BIOS
"Booting", sometimes called "Booting up" is the process that the computer completes to get it ready to use when it is first turned on. When the computer turns on, the BIOS starts up and performs a Power-On Self Test (POST). During the POST, the BIOS will check various devices in the computer like the computer processor, memory, the video card and others to make sure they are present and functioning. Once the POST has completed successfully, the BIOS looks for an operating system to load, which is usually located on the computer's hard drive. When it finds one, it starts to load it. At this point, the operating system takes over control of the system.