Name used in PCs to represent the first serial port. If you plug an external modem into the first serial port, you are connecting it to COM1. There are normally two serial ports (COM1 and COM2) in a PC, although it can support four. Some PCs have a mouse plugged into the first serial port and the modem plugged into the second port. You will need to configure your comms software so that it knows which port your modem is connected to by selecting the correct COM port.
