CMOS is a type of memory chip that stores the BIOS information. The terms often are used interchangeably.

    CMOS stands for Complementary Metal Oxide Semiconductor and is pronounced "sea moss." It describes the material out of which the chip is made. A CMOS chip will store information as long as it receives power that is usually supplied by a battery.

    The BIOS is the Basic Input Output System. On startup, the BIOS tests the system and prepares the computer for operation by searching for system components and configuring memory to access the system hardware. It then loads the operating system and passes control to it.

    The BIOS can be configured with information about system components in the Setup screen that can be accessed during bootup. Usually the F1, F2, DEL keys are used to access the BIOS Setup. Because the BIOS is stored on a CMOS chip the Setup is also referred to the CMOS Setup.