BIOSfirmware

BIOSfirmware refers to the firmware that initializes computer hardware and starts the boot process before handing control to the operating system. Historically implemented as the BIOS, this software resides in non-volatile memory on the motherboard, such as ROM or flash memory, and is executed when the computer is powered on. Modern systems increasingly use the Unified Extensible Firmware Interface (UEFI), which supersedes the legacy BIOS with a more flexible interface, larger boot volumes, and features like secure boot.

During power-up the BIOS performs POST (Power-On Self Test), detects and configures hardware components, and establishes basic I/O behavior. It also provides a firmware interface used by the operating system to access low-level hardware features before the OS kernel takes control. The BIOS stores settings in non-volatile memory, typically via a CMOSRAM backed by battery. Firmware updates are delivered by motherboard vendors and applied through motherboard utilities or BIOS flash utilities; improper updates can render a system unbootable (brick), hence recovery methods exist.

Integration with security features: UEFI-based firmware supports secure boot to ensure only signed bootloaders run. BIOS-era security included boot passwords and tamper-evident settings. BIOS and firmware updates are important for hardware compatibility and vulnerability fixes, but must be sourced from official vendors and verified for integrity. Firmware occasionally exposes interfaces for management and firmware modules (option ROMs, drivers) which can be a vector for attacks if not properly secured.