I'm not sure what you mean by "source code", but if you click on the File menu while in Front Panel or Block Diagram mode, you should see a "Print" option. Since LabVIEW is "pictorial" in nature, you can print a picture of the Front Panel, as well as picture(s) of the Block Diagram, based on the options you choose after selecting "Print". Note that really big block diagrams, particularly those with "hidden blocks" (Case statement alternatives or Stacked Sequences) can be a bit unwieldly to view (though you can choose not to print the "hidden" blocks).
Bob Schor
