Summary
Highlights
BIOS (Basic Input/Output System) is the firmware that appears on your screen when you start your computer, before the operating system loads. It's often referred to as system BIOS or ROM BIOS, although modern BIOS is stored on flash memory on the motherboard, not ROM.
The BIOS is responsible for initializing the system through a process called the Power-On Self-Test (POST). This diagnostic checks for essential components like the CPU, memory, keyboard, and mouse. If there are issues, an error message appears. After POST, the system begins to load the operating system, sometimes via a bootloader.
BIOS software is stored in flash memory on the motherboard. Some motherboards have dual BIOS chips (main and backup) to provide redundancy and protection during BIOS upgrades, allowing for recovery if an update fails.
Older PCs use a traditional or 'legacy' BIOS, which has been around for over 25 years. This type of BIOS was designed for older hardware and may not support newer components. It typically presents a text-based interface navigated with keyboard keys.
Modern computers utilize UEFI (Unified Extensible Firmware Interface) BIOS, a standard created by Intel. UEFI offers a more advanced, graphical interface that can be navigated with a mouse, and its functionality is consistent across different manufacturers due to its standardized nature.
UEFI BIOS settings include an overview of the CPU and BIOS type, connected devices (storage, audio, network), advanced features like virtualization, power options, security, and startup settings. These settings are crucial for system reliability and should only be changed with caution and proper documentation.