BIOS

BIOS is firmware that initializes a computer’s hardware during startup and provides basic services for loading an operating system.

Power-on self-test: A startup diagnostic routine that checks essential computer hardware before the operating system loads. BIOS runs this check to detect basic hardware faults during startup.
Firmware: Software stored in a device that provides low-level control of its hardware. BIOS is a specific kind of firmware stored on a computer’s motherboard.
UEFI: A standardized firmware interface that replaces legacy BIOS on most modern personal computers. UEFI offers a newer startup architecture and capabilities beyond the traditional BIOS interface.
Boot sequence: The ordered startup process that takes a computer from power-on to a running operating system. BIOS follows a configured device order when searching for startup code.
Bootloader: Software that locates and starts an operating system kernel. BIOS transfers control to boot code that begins loading the operating system.
Motherboard: The main circuit board that connects a computer’s processor, memory, storage, and peripherals. The motherboard typically contains the chip that stores BIOS firmware.
GUID Partition Table: A disk-partitioning scheme that uses globally unique identifiers to describe partitions. Modern UEFI systems commonly boot from GPT disks rather than BIOS-era MBR disks.
BIOS setup utility: A firmware interface for changing low-level computer settings before an operating system starts. It exposes BIOS options such as boot order, clock settings, and device configuration.
Master boot record: A disk structure containing initial boot code and a partition table. On legacy BIOS systems, startup code is commonly read from a disk’s first sector.
Central processing unit: The processor that executes instructions and coordinates operations in a computer. After reset, the CPU begins executing startup instructions supplied by firmware.

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