What Is the Function of the CMOS Battery?

By Staff WriterLast Updated Mar 28, 2020 6:03:03 PM ET
Marcin Jedyk/E+/Getty Images

CMOS batteries power code that runs before the operating system is loaded in a computer. Common tasks completed before your operating system loads are activating the keyboard, loading the system drives and setting the system clock. Because the system clock is controlled by a CMOS battery, one of the most common methods of identifying CMOS battery problem is noticing that your computer has a problem maintaining the correct time.