BIOS (which stands for Basic Input Output System according to ABBREVIATIONFINDER) is a program that is recorded on a chip on the motherboard, specifically in an EEPROM (Electrical Erasable Programmable Read Only Memory) memory.
The BIOS is an application (Software) that locates, recognizes and configures all the devices of a Motherboard (MB) necessary to load the Operating System in RAM. Provides low-level communication, operation, and hardware configuration of the system that, at a minimum, drives the keyboard and provides basic output (emitting normalized beeps from the computer speaker if faults occur) during startup. The BIOS is usually written in Assembly Language. The first term BIOS appeared in the CP / M operating system, and describes the part of CP / M that ran at boot time and was tied directly to the hardware (CP / M machines usually had a simple bootable loader in ROM, and nothing else). Most versions of MS-DOS have a file called “IBMBIO.COM” or “IO.SYS” that is analogous to the CP / M BIOS.
The BIOS is a basic input / output system that is often overlooked by the end user of computers. It is responsible for finding the operating system and loading it into RAM. It has a hardware component and a software component, the latter provides a generally text interface (SETUP) that allows you to configure various options of the hardware installed on the PC, such as the clock, or from which storage devices the operating system will start (HDD, ODD, FDD, USB, NETWORK etc.).
It manages at least the computer keyboard, providing even a fairly basic output in the form of sounds through the built-in speaker on the motherboard when there is an error, such as a device that fails or should be connected. These error messages are used by technicians to find solutions when assembling or repairing a computer. This resides in EEPROM memory (See Non-volatile BIOS Memory). It is a firmware type program. The BIOS is an essential part of the hardware that is partially configurable and is where the information flow processes are controlled on the computer bus, between the operating system and the other peripherals. It also includes the configuration of very important aspects of the machine.
The BIOS of a standard PC actually performs four independent functions:
Hardware Inventory and Testing Program (Power On Self Test POST)
Initial software loading process
Initialization of hardware devices that require it; loading of certain basic software, and starting the Operating System
Support for certain hardware devices of the system
BIOS access and manipulation:
To access the BIOS configuration program, generally called Setup, we will have to do it by pressing one or more keys during the computer’s startup. Generally it is usually the Delete key although this varies according to the types of plate and in laptops. Other keys used are: F1, Esc, F2 or even a combination, to find out exactly it will be enough to consult the manual of your motherboard or pay attention to the first boot screen, since a message usually appears at the bottom similar to this: Press DEL to enter Setup The general appearance of the BIOS will depend on what type you have on your board, the most common are: Award, Phoenix (have joined) and AMI. Quite similar but not the same. The BIOS program is usually in perfect English and there are also terms that are not really simple, if you do not know what you are playing consult the manual or a specialist, otherwise you will run into problems. Although they have different names, there are some sections common to all types of BIOS. A classification can be:
1 Basic parameter setting – Standard CMOS Setup.
2 BIOS Options – BIOS Features, Advanced Setup.
3 Advanced configuration and chipset – Chipset features.
4 Password, peripherals, hard drives, etc.
Normally this software is written on a non-volatile ROM (Read Only Memory) chip, located on the motherboard, hence the name ROM BIOS. This guarantees that it will not be lost when the System is turned off and that it will not depend for its performance on the existence or proper functioning of any disc, so it will always be available. The latter is important, because as we will see below, it enables the initial start-up of the equipment without the need for any external resources. From the first days of the PC’s life, the ROM-BIOS gave problems in existing equipment, since technical advances were constant; which meant increasing the disk capacities and the devices connected to the computers. This required new BIOSes, so the motherboard had to be changed, or at least in later models, change the integrated one that contained the ROM BIOS. To solve the problem, rewritable memories like EPROM (“Erasable programmable read-only memory”) and EEPROM (“Electrically erasable programmable read-only memory”) were used.
At present, a type of non-volatile memory ” flash ” (Flash BIOS) is used that can be rewritten without using any special erasing or recording device, which allows updating it very comfortably. In general, it is only necessary to “get off” from the Internet the appropriate version (usually from the motherboard manufacturer’s site) and follow the instructions that accompany the program. Due to the fact that the BIOS is constantly used in the normal operation of the PC, and that the RAM memory is faster to access than the ROM, many manufacturers require that the contents of the ROM BIOS be copied to the RAM memory as part of the boot process. initial. This is known as “Shadowing”, and it has the effect of speeding up system performance. The version of the BIOS loaded in RAM is called the shadow BIOS. Naturally this requires a realignment of the interrupt vectors so that they point to the new positions in RAM. The most modern BIOSes are called PnP BIOS or PnP-aware BIOS. Which means that they are intended to handle the PnP standard ” Microsoft’s Plug and Play “. A technology that allows a computer to identify any hardware device that is connected, and designate the necessary resources to it without conflict with the rest. Before this technology, the addition of new devices It was a real headache, given the scarcity of resources foreseen by the PC designers. For example, the well-known conflicts of interrupt IRQ’s  and of port addresses
Firmware on adapter cards
A system can contain multiple chips with BIOS firmware. In addition to the boot BIOS located on the Hard Drive and Motherboard.
The BIOS market
The vast majority of PC motherboard vendors delegate the production of the BIOS and a suite of tools to third parties. These are known as “independent BIOS vendors” or IBV (Independent BIOS vendor). Motherboard manufacturers then customize this BIOS according to their own hardware. For this reason, the BIOS update is usually obtained directly from the motherboard manufacturer. The manufacturer can publish firmware updates through its website, but poor hardware compatibility can cause a failure that spreads throughout the entire motherboard., rendering it completely useless. The main BIOS vendors are American Megatrends (AMI), General Software, Insyde Software, and Phoenix Technologies (which acquired Award Software International in 1998).