Q. What is Serial Mouse?
Mice that use standard serial port are known as 'serial'. Because Serial ports 1 and 4 (COM1, COM4 under DOS, /dev/ttyS0 and /dev/ttyS3 under Unix/GNU-Linux systems) and ports 2 and 3 (COM2, COM3 or /dev/ttyS1/dev/ttyS2) share same interrupts correspondingly one must be careful not to connect the mouse so that it shares interrupt with other device in operation such as a modem.