About Controlling Dialog Boxes With AutoLISP Programs (DCL)
This topic provides an overview to related topics that define the process you use to display dialog boxes and respond to user input from an AutoLISP program.
About Functions Restricted When a Dialog Box is Open (DCL)
While a dialog box is active—that is, during the start_dialog call—you cannot call any function that requires user input on the AutoCAD command line, or affects the display outside the dialog box (for example, in the graphics window). This restriction includes functions that write text, such as print, princ, and prin1.