The BIOS (Basic Input/Output System) is a program that a computers microprocessor uses to start the computer system after it is powered on. It is software stored on a small memory chip, also known as firmware, found on the motherboard, and it is the very first software to run after a computer starts. The BIOS performs several essential tasks, including:
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Power-On Self-Test (POST): The BIOS initializes and identifies system devices such as the CPU, RAM, video display card, keyboard, and mouse, hard disk drive, optical disc drive, and other hardware. It then checks if the system is receiving power.
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Loading the Operating System: After the POST is completed, the BIOS attempts to load the operating system through a program known as a bootstrap loader, which is designed to locate any available operating systems. If a legitimate OS is found, it is loaded into memory.
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Hardware Configuration: The BIOS is used to identify and configure the hardware in a computer, such as the hard drive, CPU, memory, and related equipment.
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Data Flow Management: The BIOS manages data flow between the computers operating system (OS) and attached devices.
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Security: The BIOS can also play a role in computer security. Most BIOS software versions have the option to password-protect the boot process, which means that you must enter a password before any BIOS activity can take place. With the BIOS performing virtually all of its functions during startup, this effectively password-protects the operation of the whole computer.
The BIOS is theoretically always the intermediary between the microprocessor and I/O device control information and data flow. Although, in some cases, BIOS can arrange for data to flow directly to memory from devices, such as video cards, that require faster data flow to be effective. The BIOS is accessed and configured through the BIOS Setup Utility, which is, in essence, the BIOS itself, and all BIOS options are able to be configured here. The BIOS software itself generally resides on a Read-Only Memory (ROM) or a flash memory chip.
