Asus BM3CD User Manual page 23

Serial ports (on selected models only). These COM ports are for pointing devices or
other serial devices.
VGA port. This port is for VGA-compatible devices such as a VGA monitor.
Air vents. These vents allow air ventilation.
DO NOT block the air vents on the chassis. Always provide proper ventilation for your
computer.
Serial port. This COM port is for pointing devices or other serial devices.
ASUS Desktop PC 23