Device 7 Details

Device 7 is the null device. Any information sent to device-7 is discarded. It is useful for writing subroutines that sometimes display information and sometimes don't. By putting the device number in a variable, the programmer can control the information is displayed or not by changing the variable  For example, the compiler normally sends its output to a disk file, but if it detects an error, it diverts the output to this null device.