After you build a VI, you can use it in another VI. A VI called from the block diagram of another VI is called a subVI. You can reuse a subVI in other VIs. To create a subVI, you need to build a connector pane and create an icon.
A subVI node corresponds to a subroutine call in text-based programming languages. The node is not the subVI itself, just as a subroutine call statement in a program is not the subroutine itself. A block diagram that contains several identical subVI nodes calls the same subVI several times.
The subVI controls and indicators receive data from and return data to the block diagram of the calling VI. Click the Select a VI icon or text on the Functions palette, navigate to a VI, double-click the VI or drag the VI to the block diagram to create a subVI call to that VI.
You can edit a subVI by using the Operating or Positioning tool to double-click the subVI on the block diagram. When you save the subVI, the changes affect all calls to the subVI, not just the current instance.
When LabVIEW calls a subVI, ordinarily the subVI runs without displaying its front panel. If you want a single instance of the subVI to display its front panel when called, right-click the subVI icon and select SubVI Node Setup from the shortcut menu. If you want every instance of the subVI to display its front panel when called, select File»VI Properties, select Window Appearance from the Category pull-down menu, and click the Customize button.