A computer must start without power and use programs to turn itself on and setup all the hardware for use with the operating system and software programs. The term used for this process is bootstrapping. The metaphor is of a person wearing boots pulling oneself up without assistance. This expression may sound dated now but was in common usage during past decades when computers were first designed.
Changing boot loaders can be scary for people that do not understand the process. In addition to boot loaders often times partitions must be allocated and formatted, putting in jeopardy all data on all disks. Some mistakes at this level can be undone with prior planning, others are irreversible. Tested backups allow for worry free changes but few people take the time and/or have the hardware ready to do so easily. The following is the order in which the programs are invoked.
- BIOS/Firmware, which drive to use
- Storage devices, holds a boot loader
- Boot Loader, the first program from disk passing control to an OS
- Kernel/Plumbing, the first part of an OS
- Operating System, the rest of the OS