BIOS is an acronym for for Basic Input/Output System.

The BIOS is a type of firmware used during the booting process (power-on startup) on IBM PC-compatible computers. Like any DOS, FreeDOS uses BIOS for certain functionality.

Note that many new (2010 and later) computers instead use UEFI, which may provide BIOS emulation using "Legacy" mode. However, computers manufactured after 2020 may no longer provide "Legacy" mode.