AutoLISP
Developer's Guide > Using the AutoLISP
Language > AutoLISP
Basics > Basic Output
Functions > Displaying
Messages >
Exiting Quietly
If you invoke the princ function without passing an expression to it, it displays nothing and has no value to return. So if you write an AutoLISP expression that ends with a call to princ without any arguments, the ending nil is suppressed (because it has nothing to return). This practice is called exiting quietly.