Greetings guys, I’m here with a new topic. I will talk about the BIOS (Basic Input / Output System) that everyone is aware of but does not know exactly what it does. Let’s first look at where this BIOS came from.

The BIOS was first developed by Gary Kildall, founder of Digital Research, for the CP / M operating system in 1975.

So what does this BIOS do? BIOS is actually as important to a computer as a chipset, processor or motherboard. In other words, it should not be called a tiny chip or software. Let’s see what it does.

From the moment the computer starts:

Starts the system.

Introduces the hardware to the processor sequentially, that is, loads its drivers. While loading the drivers, it pulls the driver for that hardware via the ROM in any hardware (eg a keyboard) and introduces this driver to the processor. It tests all drivers and functions while the system is booting. For example, in most computers, when the keyboard is not attached, an error such as “Keyboard Error” appears at system startup. Or, if the bootloader of the operating system to be booted due to MBR is not found, it gives an error in the form of “Boot Failture”. Here it is determined by testing. How much voltage will be supplied to which equipment and which mode will be operated determine them. It boots the bootloader of the operating system (in simple words, it starts the operating system.)

Now let’s take a look at the parts of the BIOS. It basically consists of two parts. ROM and CMOS RAM.


The partition we call ROM is a fixed and unchangeable partition. So to give an example, when we enter the “BIOS Setup” section, there is that interface that we come across, or that interface, which is usually blue and gray. This and this type of data is stored in ROM. Of course, let’s open the matter a little more. There are also varieties of ROM:

ROM (read only, cannot be changed, data cannot be written)

PROM (programmable)

EPROM (can be erased)

EEPROM (Flash ROM, electrically erasable)

The BIOS chips we use today can be updated over the internet. So we have all seen it, sometimes there are updates of the BIOS. This is the difference between old chips and new ones, normally no data can be written on ROM but read-only. However, the data we use today are designed to be written on. If we understand the ROM issue, let’s move on to CMOS RAM.


If it is CMOS RAM, you know, we change the settings in the BIOS Setup, for example, we put our flash memory to the top while formatting, just like this, everything we can set is written to CMOS RAM. They are not permanent and are variables. We can reset the CMOS RAM by removing and installing the BIOS battery.

Let me touch on one more thing. Above, I said that Roms on the hardware are read and introduced to the processor. BIOS doesn’t just load drivers over hardware. There are also virtual drives installed on the computer. For example, if you have dealt with virtual machines, you know. Vmware program has virtual drivers, we install them on the hard drive while the program is being installed. The BIOS reads these virtual drives from the hard drive and introduces them to the processor while the computer is starting. Of course, this driver identification process does not only occur while the computer is booting. For example, flash drives have a plug-in feature, so plug and play. Here, as soon as you insert the flash memory while your computer is on, the BIOS reads the ROM in the flash memory and identifies that drive to the processor, then you start to read the data in it.

We can call the BIOS the most basic building block of a computer. Because a computer cannot work without a BIOS.


Finally, the structure we call BIOS is a small chip on the motherboard. Some models are soldered to the motherboard (cannot be removed by hand) and some models can be plugged in and removed. The only difference between the removable ones is that they are easy to repair.

See you in my next post. Good work to everyone.

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