• The first routine accepts the call as it is passed from IDL
  
  
• Calls the routine as the Fortran programmer would normally write it
  
  
• Watch out for all of the directives (!dec$ is still legal!)
  
  
• Watch out for the %val intrinsic
  
  
• Watch out for the names of the routines (the use of the trailing _ is somewhat arbitrary)
  
  
• The use of leading _ is not arbitrary - it is how DVF deals with routine names
  
  
• Requires a .def file so that the linker knows how to build the dll
  
  
• Routines can be functions or subroutines