ON TIMEOUT defines an event branch to take when an I/O operation on the specified interface fails to responded within the specified number of seconds. The value of seconds can range from 0.001 to 32.767 but is rounded to the timing resolution of the computer. The ON TIMEOUT statement must be executed before the I/O statement. If an ON TIMEOUT is not specified for a particular interface and a device does not respond to an I/O action, the computer will wait forever. Pressing the CLR I/O key will abort such an infinite wait.