CMOS and BIOS are often used interchangeably, but you can think of the BIOS as software, and CMOS as the hardware running it. If someone tells you to “go into your computers CMOS,” or to “go into BIOS and change something”, they probably mean the same thing: Enter the low-level settings on your PC to make modifications.
CMOS
Abbreviated from Complementary Metal Oxide Semiconductor, it’s usually pronounced “see-moss”. CMOS is defined as one of two things:
1) CMOS is the hardware in your PC that performs very low-level functions and very basic computer start routines. The CMOS does things like maintain your PCs clock, and provides an interface to the rest of the PC hardware for the BIOS to do its job. It requires very little power to operate.
2) CMOS is also a type of light-sensitive sensor in imaging technology that acts similar to a CCD. Put simply, it acts as a digital camera’s “film”, and captures a photo for your camera. Read more about digital cameras and CCDs here.
BIOS
Abbreviated from Basic Input / Output System, it’s usually pronounced “bye-ohs”. The BIOS is an interface that allows a user to make low-level changes to a PC’s motherboard, CPU, memory and other devices. Unless you know what you’re doing, you don’t need to change these; the default BIOS settings are usually set just right. In some cases, you may need to “update the BIOS”, or “flash the BIOS”. Upgrading the BIOS means running a special program that replaces the programming of the BIOS on your PC with something newer. I recommend you do this only if instructed or you’re doing this to fix something. A BIOS upgrade is very delicate – if something goes wrong during the process, you may stop your computer from functioning.