A Laptop has 2 different types of batteries. The big one powers all of the components including the CPU and Hard drive, while the smaller one powers the motherboard. Unlike the bigger battery which is bigger and heavy, the CMOS battery is small and lives on the motherboard.
Computer BIOS
Since the CMOS battery powers the BIOS system, it is fitting we get to understand what the BIOS is.
A BIOS is the software component of a computer that comes pre-installed and hard-coded meaning it can not be uninstalled nor reinstalled like the operating system. It stands for Basic Input/Output System.
The BIOS is responsible for managing a computer’s exchange of information and output, especially when booting the computer.
For example, when you press the power key before the computer receives the power supply, it is the CMOS battery that gives the board enough power to process that “pressing of the button” and eventual turning on of the computer. Pressing the power button is input while booting the computer is output.
More about the CMOS battery
CMOS stands for “Complementary Metal Oxide Semiconductor.” they can be found on both laptops and desktop computers.
The CMOS battery gets charged whenever your laptop is plugged in. It’s only when your laptop is unplugged that the battery loses charge. Most batteries will last 2 to 10 years from the date they’re manufactured. The more you leave your laptop plugged in, the longer your battery will last. The typical NVRAM capacity is 256 bytes.
New word: Data flow – Input/Output.
Resources
https://www.hp.com/us-en/shop/tech-takes/what-is-cmos-battery-how-to-remove-and-replace
Sophie Obomighies technical blog 
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