CMOS stands for Complementary Metal Oxide Semi-Conductor. It is an on board semi-conductor chip powered by a CMOS battery. CMOS uses a complementary arrangement of NMOS and PMOS, Negative and Positive Metal Oxide Transistor Circuit.
CMOS memory is used to store the configuration information of our computer and its electrical current is supplied by battery backup when our computer is turned off. The CMOS setup is the part of the BIOS program. The CMOS memory is usually located with the real time clock in the mother board chip set or in a separate real time clock chip.
Real Time Clock (RTC) Circuit
The real time clock is the calendar and watch of the computer. The real time clock chip is a battery operated chip that maintains basic setting and the system time.