You may hear both CMOS and BIOS used interchangeably in certain circumstances, such as resetting the BIOS and clearing the CMOS. The two are related, but they are separate items. The Basic Input Output System (BIOS) is firmware stored in a chip on the motherboard, and it runs first during the boot process. The firmware tests the PC's hardware and then launches the bootloader if more than one operating system exists, or it opens the operating system installed, whichever applies. The BIOS includes a graphical user interface (GUI) accessible by pressing a hotkey during bootup, typically set as F2, F12, or Delete. Inside the GUI, you find all hardware information and configuration options. Complementary Metal-Oxide-Semiconductor (CMOS) got named after the manufacturing process for making electronic boards, PC RAM, and other peripheral boards. The CMOS in a PC is similar to RAM, except it retains data when the PC is off, plus it has a minimal capacity (usually 256 bytes). CMOS stores the data and time, the boot sequence, and disk drive information. The rest is stored and managed by the BIOS. Therefore, the two items work together to boot your PC successfully.