Functioning of BIOS

The Basic Input/Output System (BIOS) plays a pivotal role in the initiation and orchestration of a computer’s fundamental operations. The main functions of BIOS are as follows:

1. Power-On Self-Test (POST) –

When a computer powers on, the BIOS takes charge of executing the Power-On Self-Test (POST). This sequence of diagnostic tests is designed to assess the integrity of essential hardware components.

The processor, memory, storage, and peripheral devices undergo scrutiny. Successful completion of the POST prompts the BIOS to proceed with loading the operating system. In case of failures, the BIOS communicates hardware issues through error codes or audible beeps.

2. Bootstrap Loader –

Following a successful POST, the BIOS embarks on locating the bootloader – a small program responsible for loading the operating system into the computer’s memory.

The bootloader is typically situated in the Master Boot Record (MBR) or the EFI System Partition (ESP) on the storage device. Once found, the BIOS transfers control to the bootloader, initiating the loading of the operating system kernel into memory.

3. Interrupt Handling –

BIOS takes charge of managing interrupts generated by both hardware and software events. Interrupts are signals that temporarily halt the normal execution of a program to address a specific event.

Interrupt Type	Description
Hardware Interrupts	Signals from devices, managed for immediate attention.
Software Interrupts	Invoked by software or OS requests, coordinated by BIOS.
Timer Interrupts	System timer-based interrupts, utilized for time-sensitive operations.
Keyboard Interrupts	Handles interrupts from the keyboard for user input.
Disk and Storage Interrupts	Manages interrupts related to disk and storage devices.
System Management Interrupt (SMI)	Special interrupts for critical system management tasks.
RTC (Real-Time Clock) Interrupts	Manages interrupts related to the Real-Time Clock (RTC).
Power Management Interrupts	Handles interrupts related to power management features.
I/O Interrupts	Manages interrupts for communication with external devices.
Memory Access Interrupts	Handles interrupts related to memory access and operations.
Error Interrupts	Manages interrupts triggered by system error

The BIOS incorporates routines to handle these interrupts and serves as the intermediary between software and hardware, ensuring smooth communication.

4. CMOS Setup Utility –

Users can interact with the system’s configuration through the CMOS Setup Utility during the boot process. This user-friendly interface empowers users to modify various system settings, including the boot order, date and time, and hardware parameters. Changes made through the CMOS setup are stored in the CMOS memory, providing persistent customization.

5. BIOS Configuration –

The BIOS extends a set of configuration settings that users can tailor to adjust the system’s behavior. These settings encompass parameters related to CPU speed, memory timings, and other hardware-specific configurations. Advanced users can access and modify these settings through the BIOS setup interface, offering avenues for system optimization or overclocking.

What is BIOS?

The Basic Input/Output System (BIOS) is a fundamental component of computer systems, serving as a bridge between the hardware and the operating system. This critical firmware is embedded in the motherboard, providing essential functionalities for the system’s initialization and operation.

It performs the critical function of initializing and testing the system’s hardware components, such as the bio mass index of the computer’s architecture, and loading the operating system into the computer’s memory upon startup.

In this article we will learn and explore, the history, architecture, functioning, and significance of BIOS in modern computing.