5. The BIOS confirms there's a bootstrap loader, or boot loader, in that first sector of the boot disk, and it loads that boot loader into memory (RAM). The boot loader is a small program designed to find and launch the PC's operating system.6. Once the boot loader is in memory, the BIOS hands over its work to the boot loader, which in turn begins loading the operating system into memory.When the boot loader finishes its task, it turns control of the PC over to the operating system. Then, the OS is ready for user interaction.