Acronym for Complementary Metal Oxide Semiconductor (pronounced ‘see-moss’). A special type of semiconductor with very low power consumption among other things. They are constructed very differently from a typical ‘transistor’ or ‘integrated circuit,’ but perform many of the same functions. CMOS chips are widely used in computing products. One specific area concerns the BIOS or preferences for some of the basic functionality of a computer. These are sometimes stored in CMOS-based memory chips, which are kept under power by a small battery somewhere in the computer.