The BIOS and CMOS are frequently considered to be the same thing, but they are not. They are different components of a computer, but they together work to function the computer properly.

The BIOS which is a computer chip on motherboard that looks like the above picture. This chip consists of a special program which helps the computer processor interaction and organize the other components in the computer. These other components include USB ports, network cards, video cards, sound cards, floppy drivers, disc drivers , hard drivers, and others. Without using BIOS , the processor don’t know how to interface with the computer components, and the computer can not be  able to work.


The CMOS is also another type of computer chip on the mother board, but more specially, It is a RAM chip. This is one type memory chip has the capacity to store information about the computer components, and also settings for those components. However, basic RAM chips lose the data stored in them when power is off. To hold the information contained in the CMOS chip, a CMOS battery on the mother board supplies continuous power to that CMOS chip. If the battery is detached from the mother board or it is not in a running conditioning, the CMOS will lose the information contained in it. Any settings which you made in the CMOS setup will be lost, and you need to make those settings changes after another CMOS battery was put on the mother board. For example a dead CMOS is off for a long time the time and date settings will rearrange to the manufactured date.

The BIOS program on the BIOS chip reads information from the CMOS chip when the computer is starting up, during the boot up process. You may notice on the initial start up screen, called the POST screen, an option is available to enter the BIOS or CMOS setup. When you enter this setup area, you are entering the CMOS setup, not the BIOS setup. The BIOS chip and program cannot be updated directly by a user. The only way to update the BIOS is using a BIOS flash program called a BIOS update, which updates the BIOS to a different version. These updates usually are provided by either the motherboard manufacturer or the computer manufacturer.