BIOS Full Form Basic Input/Output System (original) (raw)

Last Updated : 12 Jul, 2025

**BIOS stands for **Basic Input/Output System. BIOS is the first program to run when the computer starts. It is a ROM chip (EEPROM chip) found on motherboards and is used for hardware initialization during the booting process. It is pre-installed in the computer system. When BIOS boots up the computer system, it checks if all of the components are in place and working, and then it loads the operating system into the computer's RAM from the hard disk of the system. Nowadays BIOS is written on flash memory, to ease the process of rewriting the BIOS chip, whenever needed.

History of BIOS

BIOS was first introduced in 1975, in the CP/M Operating System. Control Program for Microcomputers, was developed for Intel 8080/85-based microcomputers by Gary Kildall of Digital Research, Inc. The system had a simple bootloader in its ROM.
IBM classified the system bios into two categories when PS/2 machines were introduced:

• **CBIOS: CBIOS stands for **Compatibility BIOS. The real-mode portion provided backward compatibility with current operating systems and thus was named CBIOS.
• **ABIOS: ABIOS stands for **Advanced BIOS. It provided new interfaces, especially the one suited for multitasking OS.

Functions of BIOS

• **POST: Power on Self-Test is the process performed by BIOS immediately after the computer system starts to check any hardware-related issues. if any error is found in this process, the system alerts through flashing LEDs, audible beeps, or error messages on the monitor, all of which are technically referred to as POST codes, beep codes, and on-screen POST error messages, respectively.
• **Bootstrap Loader: The bootstrap program stored in ROM is loaded in the hard drive, as soon as the computer starts. The bootstrap loader locates the operating system and passes the control to it.
• **Bootstrap Driver: Bootstrap Driver configures basic hardware so that the system can run. They are low-level drivers and give basic information about computer hardware.
• **CMOS Setup: Complementary Metal-Oxide Semiconductor (CMOS) chip, saves some system information, such as the time, date, and other essential system settings. CMOS chip is powered by the battery located in the motherboard. It also stores some information about hardware. The chip's content is copied to the RAM(main memory) of the system to increase the speed since the CMOS chip is quite slow. It is because the BIOS and CMOS, setup configure the system’s crucial information like the password, date, and time.
• **Boot device selection: One of the CMOS's most important roles is, it can alter the device boot process. This is important for system restoration because the CMOS may need to change boot priority from the hard drive to the optical drive or flash drive to launch the operating system installer or adjust which hard drive to load the operating system from.

Working of BIOS

• A **Basic Input/Output System (BIOS) is a kind of program that can be accessed by the EPROM (Erasable Programmable Read Only Memory) chip. Upon switching on the system, the control is passed to the BIOS Program in a similar place on EPROM.

**The working of BIOS is mentioned below:

• **Power: Upon turning on the computer, BIOS starts running.
• **Power-On Self-Test (POST): BIOS will perform some security checks and make sure that all essential components (RAM, CPU, Storage devices, etc.) are working properly. On getting any issue, it usually beeps or give some error message.
• **Identify Boot Device: Upon getting confirmation that everything is okay, BIOS looks for Bootable device like USB Drive, CD/DVD.
• **Load the Bootloader: Once the BIOS finds the boot device, it runs small program called bootloader that is responsible for loading the OS.
• **Start the OS: Now, the bootloader has responsibility of loading the OS into memory and after which you are able to start the computer.
• **BIOS Setup Utility: BIOS Setup Utility can be accessed ( keys like F2, F10, or Delete during start) that helps in changing boot order and system time.
• **Ongoing Hardware Communication: Throughout the operation of computer, BIOS helps OS to communicate with the hardware and make sure everything runs smoothly.

Features of BIOS

• Every BIOS implementation is specifically designed for a particular type of motherboard model or particular computer.
• Originally, BIOS firmware was stored in the ROM memory but nowadays it is stored in Flash memory so that it can be rewritten without removing the chip from the motherboard.
• The other reason for doing this is that it allows easy updates of BIOS firmware, so new features can be added and bugs can be fixed.
• The latest advancement of BIOS is UEFI(Unified Extensible Firmware Interface).

Accessing BIOS

With BIOS, many computer applications are not having any restrictions to keep the details of the hardware, attached I/O device, etc. Consumers have access to BIOS and also the configuration of BIOS. Some of the steps mentioned below help in setting up the BIOS.

How to Setup BIOS?

**Step 1: First turn off your computer or simply restart it.

**Step 2: When the system turns On, wait for the message similar to 'entering setup' to come.

**Step 3: Wait for the message 'Press Key to enter BIOS Setup'. Some keys are like Del, Tab, etc.

**Step 4: Press the specified key as early as possible.

**Step 5: Process Complete.

BIOS Security

BIOS Security is an advanced feature of cybersecurity. It has the work to protect the Operating System from suspicious activities. Plundervolt is one of the manipulations of BIOS which is used to manage computer power supply at the time of memory writing, that has the work to maintain the security gaps which overall results in improving the security of the BIOS.

BIOS Manufacturers

IBM was the first organization that single-handedly owed the BIOS. In spite of IBM, there were several other companies like Phoenix Technologies have their own BIOS. There are several companies that are producing motherboards with embedded BIOS chips in them. Some of the companies are HP, Ricoh, etc. Each organization has its own drivers of motherboards, and each of them creates it in a unique way.

Conclusion

**BIOS (Basic Input/Output System) is a crucial component that acts as the bridge between a computer's hardware and its operating system. It initializes and tests hardware during startup, loads the operating system, and allows users to configure basic system settings. Understanding how BIOS works helps users troubleshoot issues and better manage their hardware.