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A basic input/output system (BIOS) is a preinstalled program used during startup on Windows-based computers. The CPU initially accesses the BIOS, after which the operating system is loaded.
A basic input/output system is also known as system BIOS or ROM BIOS.
The BIOS is built-in software that contains generic code required to control the keyboard, display screens, disk drives and other functions. The primary purpose of the BIOS is to set up hardware and further load and start an operating system. BIOS is placed in a nonvolatile ROM chip inside the computer, ensuring the availability of BIOS at all times and preventing accidental disk failure. The BIOS checks every hardware connection and locates the devices, after which the operating system is loaded into computer memory.
BIOS software is designed to work with the various devices that make up a complimentary system chipset. The BIOS library has certain functions used to operate and control system peripherals, which can be initiated by an external software.
Users using the BIOS user interface can perform functions such as:
Modern PCs have BIOS stored in rewritable memory, permitting contents to be rewritten or replaced. Such content rewriting is called flashing and is executed through a special program provided by system manufacturers.