From HomoExcelsior

1. To enter (a program) into a computer using a few initial instructions. 2. Abbreviation of bootstrap meaning to self-initialize, start on one's own, begin without outside assistance. 3. Operating Systems; to load a small initiation program responsible for reading the full operating system into a machine. 4. Operating Systems: the beginning stage of operation where processes are started before users begin logging in.

In modern PC machines the way a computer boots is roughly:

A BIOS (basic I/O system), stored in ROM, contains the program that checks the disk drives for a MBR (master boot record). The program found at the MBR is the boot loader which is specific to the OS being booted. The boot loader finds the OS and prepares the hardware (memory, disk, etc.) for starting the OS. The OS finishes initializing itself then starts optional services and device drivers before the machine begins to respond to normal input.

In the case of a network boot, where a machine may be diskless, the sequence is essentially the same, but the BIOS is in the ROM of a network card which fetches the boot loader program from the network.

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