In this section:
PRINTER_OPEN displays the standard Windows 'Print' dialog that enables the user to select a printer. The function takes two arguments. The first is an integer that is the Fortran unit number on which to open the printer. The second argument is a call-back function supplied in the program. If the printer is successfully selected, the call-back function is called. (The value returned by the call-back becomes the value returned by the enclosing winio@. Hence, a return value of 1, for example, has the effect of keeping the parent window open). If no printer is selected, PRINTER_OPEN returns 1 to keep the window open. The call-back function should perform print operations using standard Fortran output statements (for example, WRITE) on the specified unit number. It is necessary to CLOSE the unit number in order to dispatch the output to the printer.