CMOS

Another important type of firmware is CMOS (complementary metal-oxide semiconductor). The
CMOS chip retains settings such as the time, keyboard settings, and boot sequence. The CMOS also stores interrupt request line (IRQ)and input/output (i/o) resources that the BIOS uses when communicating with the computer's devices. The CMOS chip is able to keep these settings in the absence of computer power because of a small battery, which is usually good for from two to ten years.
You can view and modify the computer's CMOS settings by entering the computer's setup program during bootup. When booting up the computer, watch the screen for instructions such as "Press -to access Startup configuration" or " Press CTRL S DELETE to enter setup." You will only have about three seconds to enter the appropriate key combination from the time such a message first displays. You can
configure the length of this delay in the CMOS settings.