The Complementary Metal-Oxide Semiconductor , also known as CMOS is an on-board battery powered semiconductor chip that stores information in your computer, it is also known as 
(RTC) real time clock, CMOS RAM or (NVRAM) non-volatile RAM.
This small metallic object, helps to store information like, system hard ware settings and system time and date.
CMOS batteries come in different forms, some are soldered on the board, some are fixed in a small round plastic case or comes with wire where it is fixed into a small port in the board. Whichever form you find them, they perform the same functions.
