A computer chassis, also known as a computer case or base unit, is an enclosure containing the majority of a computer's core components. Typically, a chassis is built from steel or aluminum, though some home-built computer cases have been manufactured from materials like glass or wood. While some mistakenly refer to the chassis as a computer's hard drive or CPU, it is its own distinct entity.
A computer chassis is commonly comprised of sheet metal enclosures, which provide drive bays and a power supply. Rear panels help to contain peripheral connectors that protrude from expansion slots and the computer's motherboard. Power status is indicated by switches or buttons, LEDS and a "reset" button. Most chassis are also equipped with dust filters, placed before the air intake fans.
Computer chassis come in a varied range of sizes, known commonly as form factors. The computer's motherboard is typically what determines the shape and size of a chassis, as it is the largest piece of most computer systems. Layout and internal dimensions are often specified with cases, though form factors of blade servers and rackmount chassis are often equipped with exact external dimensions, as they must fit within specific enclosures.
Power supply unit mounting points vary between models and cases, though the top and bottom of the chassis are often the most common locations for these units. Drive bays are often found on the front side of the chassis, as well as LEDs and logistical buttons. Vents are located in various locations on the chassis, allowing for cool air to access the case and hot air to be released. Larger vents may allow for cooling fans.