It is usually the first software to run after power-up or re-start. A Boot Loader mainly manages and executes the Boot sequence of a computer system. When a computer system is power up or restarted, the Basic Input and Output System (BIOS) performs many initial tests and then transfer control to the main Boot Loader. A Boot Loader is associated with only one or a specific Operating System at a time.

It may be possible that a computer system is equipped with two different Operating System. So in this condition, either one or another will load, depending on the user preference or what has been pre-programmed to start automatically. If a computer is to be used with LINUX, a special Boot Loader installation is required. The most common Boot Loader is known as Linux Loader (LILO) and LOAD Linux (LOADLIN). LILO is the most popular Boot Loader among LINUX users. With RED HAT LINUX, another Boot Loader i.e., GRand Unified Bootloader (GRUB) is used.