Cover Everything About BIOS | What is BIOS and What Does BIOS Mean in A PC

Lucien updated on Aug 01, 2022 to Knowledge Center

Windows BIOS

BIOS is an acronym for "Basic Input Output System." On IBM PC compatible systems, it is an industry-standard firmware interface. [1] The word BIOS first appeared in the CP/M operating system in 1975. [2] BIOS is the first piece of software loaded when a personal computer starts up.

It is a set of programs that are solidified on a ROM chip on the computer's motherboard. It saves the computer's essential input and output programs, the self-checking program after booting, and the self-starting system program. It can be read and written from CMOS. Specific information about system settings. Its primary function is to provide the lowest-level, most direct hardware setup, and control for the computer. In addition, the BIOS also provides some system parameters to the operating system. The BIOS hides changes to system hardware, and programs use BIOS functions instead of directly controlling the hardware. Modern operating systems ignore the abstraction layer provided by the BIOS and directly control hardware components.

Today, this system has been the target of some virus Trojans. Once this system is destroyed, the consequences are unimaginable.

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History of BIOS

BIOS (Basic Input/Output System) was initially coined by Gary Kildall and first appeared in the CP/M operating system in 1975. Describes the hardware that the interface loads directly when the machine-specific part of the CP/M starts up. (A CP/M machine usually has only a simple bootloader in the ROM).

Various versions of MS-DOS, PC-DOS, or DR-DOS contain a file called "IO.SYS," "IBMBIO.COM," "IBMBIO.SYS," or "DRBIOS.SYS"; this file It's called "DOS BIOS" (also known as "DOS I/O system"), and it contains the lower-level hardware-specific parts of the operating system. It is specific to the underlying hardware but is independent of the operating system and is solidified in the ROM "system BIOS," and together, it stands for "CP/M BIOS."

With the introduction of PS/2 machines, IBM divided the system BIOS into real and protected mode sections. The fundamental mode is partly designed to provide

Some operating systems such as DOS have backward compatibility and are therefore named "CBIOS" (for compatibility BIOS),

And "ABIOS" (Advanced BIOS) provides an interface for new operating systems such as OS/2 for multitasking.

Since 2000, Intel has invented the Extensible Firmware Interface (Extensible Firmware Interface) to standardize the development of BIOS. The BIOS that supports the EFI specification is also called EFI BIOS. Later, to promote EFI, many well-known companies in the industry jointly established the Unified Extensible Firmware Interface Forum (UEFI Forum). Intel contributed the EFI 1.1 specification to the industry to formulate a new international standard UEFI specification. The latest version of the UEFI specification is 2.3.1. Intel has predicted that in 2010, more than 60% of personal computers in the world may use BIOS products that support the UEFI specification.

How to Enter BIOS Mode and When to Use It

Different BIOS has different entry methods. Usually, there will be a prompt on the boot screen.


Award BIOS: Press the "Del" key
AMI BIOS: Press the "Del" or "ESC" key
Phoenix BIOS: Press the "F2" key
Acer: Press the "Del" key

other machines

IBM (press f1 at cold boot, some new models can start by pressing f1 when restarting)
hp (f2 on startup and restart)
sony (press f2 on startup and restart)
dell (f2 at startup and restart)
Acer (f2 on startup and restart)
Toshiba (press ESC then f1 on cold boot)
hp Compaq (press f10 when power on until the flashing cursor appears in the upper right corner, or press f10 when power on)
Fujitsu (press f2 at startup and restart)
The vast majority of domestic brands (press f2 on startup and restart)

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Main Functions of BIOS (Basic Input/Output System)

Functionally, the BIOS is divided into three parts:

Self-check and initialization

This part is responsible for starting the computer and has three specific parts:

Windows BIOS Mode

The first part can test the hardware when you power on the computer, called Power On Self Test (POST for short). The function is to check whether the computer is in good condition. Usually, a full POST will include testing the CPU, 640K basic memory, extended memory above 1M, ROM, motherboard, CMOS memory, serial and parallel ports, graphics card, soft disk subsystem, and keyboard. Once a problem is found in the self-test, the system will give a prompt message or Whistle warning.

The second part is an initialization, including creating interrupt vectors, setting registers, initializing and detecting some external devices, etc. An essential factor is BIOS settings, mainly for some parameters of hardware settings, which will be read when the computer starts. These parameters are compared with the actual hardware settings. If they do not match, it will affect the system's startup.

The third part is the boot program, which guides DOS or other operating systems. The BIOS first reads the boot record from the start sector of the floppy disk or hard disk. If it is not found, it will show that there is no boot device on display. If the boot record is found, it will transfer the control of the computer to the boot record, and the boot record will move the operating system. Loaded into the computer, after the computer starts successfully, this part of the BIOS task is completed.

Program Service Processing

Program service handlers are mainly for application programs and operating systems. These services are primarily related to input and output devices, such as reading disks, outputting files to printers, and so on. The BIOS must deal directly with the computer's I/O devices to complete these operations. It issues commands through ports, transmits and receives data from various external devices, and enables programs to operate independently of specific hardware.

Hardware interrupt handling

Hardware interrupt handling

The hardware interrupt processing deals with the requirements of the PC hardware. The service function of the BIOS is realized by calling the interrupt service routine. These services are divided into many groups, each with a particular interrupt. For example, for video service, the interrupt number is 10H; for screen printing, the interrupt number is 05H; for disk and serial port services, interrupt 14H, etc. Each group is subdivided into different service numbers according to specific functions. Which peripherals and operations the application needs to use only need to be described in the program with the corresponding instructions, without direct control.

Although the two functions are two independent contents, they are closely related in use. These two parts are software and hardware services combined to make the computer system usually run.

In addition, it should be noted that improper BIOS settings will directly damage the computer's hardware and even burn the motherboard. It is recommended that those who are unfamiliar should modify the settings carefully.

Users can change various settings by setting the BIOS, such as the memory size of the onboard graphics card. All operating systems in the hands of the user are transferred from the BIOS to the boot sector and then moved from the boot sector to each partition to activate the corresponding operating system.

More Functions of BIOS


Setting method to boot from hard disk:

Press the "Del" key when booting up to enter the BIOS settings, (/*may also press F1, Esc, or F12, to perform specific operations*/)
Use the up and down cursor keys to move to the second item
"Advanced BIOS Features"
Press Enter, and then press the up and down cursor keys to move to
"First Boot drivers,"
this time put
Press the "Page UP" key and "Page DOWN."
Select property as
Press F10 to save and restart.
(Because the hard disk startup in different properties of BIOS is also other.)

New Generation

Next-Generation BIOS: UEFI BIOS

The BIOS that has been all-powerful in the IT industry is about to be eliminated by UEFI BIOS, and new motherboards will popularize UEFI BIOS. MSI said that UEFI BIOS would replace BIOS within three years. UEFI BIOS is "Unified Extensible Firmware Interface" (Unified Extensible Firmware Interface), a standard describing a new type of interface in detail. This interface is used for the operating system to automatically load from a pre-boot operating environment onto an operating system, simplifying the boot procedure and saving time.

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