What is CMOS?

 in Basics  tagged CMOS / CMOS battery / password by (updated 2926 days ago)

When your computer starts, press delete. You’ll enter into a blue screen which will have many options in it.
Like the one given below.

CMOS features.

CMOS features.

Can you see something called as CMOS?
Have you ever wondered:

  • What CMOS is?
  • Why is it used?
  • Why is it so important?

What is CMOS?

CMOS stands for Complementary Metal-Oxide Semiconductor.
CMOS is also called as Non-Volatile Memory ( Memory which has information, even after the Computer is shut-down). So any information previously stored in CMOS is is still there when you start the machine.

How does it work??

CMOS battery supplies the power to CMOS chip.
NOTE: CMOS battery is Not CMOS.
These are two different things. The battery powers CMOS onboard chip.

Why is CMOS used?

  • Since its a non-volatile memory, the Administrator password that comes up when you boot your machine is stored in CMOS. If you ever forget that password, you can remove the CMOS battery and insert it after five mins.
  • CMOS also stores all the current system configuration and time and date.When your machine starts, BIOS takes all the startup settings from CMOS and executes them. This is how your
    computer boots.
  • Suppose you shut down your computer at 8:00 pm today. Tomorrow at 10:00 you start your computer, and it will show you the current time and date.All this while your computer was off, so how did it know what date and time it is?
  • The battery provides this information. CMOS battery also works as a Real-time clock, keeping track of the Time and Date.

Why does it matter?

Now you know, CMOS is a non-volatile memory that stores your system settings, passwords, and works as a real-time clock. So what will happen if you remove the battery?

  • Well, every time you start your machine, you’ll have to set date and time manually.
  • The password you kept to secure your device from unauthorized access would be gone.
  • The BIOS will start your machine with the default settings, and your personalized setting would be gone.
  • If the virus affects your CMOS, your computer won’t boot at all.
    The virus will corrupt the settings, and BIOS cannot read the information there.

How long does a battery last?

The small CMOS battery lasts for about ten years.

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