2.3 Using subvis

After you build a VI and create its icon and connector pane, you can use the VI as a subVI. To place a subVI on the blockdiagram, select Functions>>All Functions>>Select a VI . Navigate to the VI you want to use as a subVI and and double-click to place it on the block diagram.

You also can place an open VI on the block diagram of another open VI. Use the Positioning tool to click the icon in the upper right corner of the front panel or block diagram ofthe VI you want to use as a subVI and drag the icon to the block diagram of the other VI.

Opening and editing subvis

To display the front panel of a subVI from the calling VI, use the Operating or Positioning tool to double-click the subVI on the block diagram. You also canselect Browse>>This VI's SubVIs . To display the block diagram of a subVI from the calling VI, press the <Ctrl> key and use the Operating or Positioning tool to double-click the subVI on the block diagram.

Any changes you make to a subVI affect only the current instance of the subVI until you save the subVI. When you savethe subVI, the changes affect all calls to the subVI, not just the current instance.

Setting required, recommended, and optional inputs and outputs

In the Context Help window, which you can access by selecting Help>>Show Context Help required terminals appear bold, recommended terminals appear as plain text, and optional terminals appear dimmed. Thelabels of optional terminals do not appear if you click the Hide Optional Terminals and Full Path button in the Context Help window.

You can designate which inputs and outputs are required, recommended, and optional to prevent users from forgetting towire subVI terminals.

Right-click a terminal in the connector pane and select This Connection Is from the shortcut menu. A checkmark indicates the terminal setting. Select Required , Recommended , or Optional .

For terminal inputs, required means that the block diagram on which you placed the subVI will be broken if you do not wirethe required inputs. Required is not available for terminal outputs. For terminal inputs and outputs, recommended oroptional means that the block diagram on which you placed the subVI can execute if you do not wire the recommended oroptional terminals. If you do not wire the terminals, the VI does not generate any warnings.

LabVIEW sets inputs and outputs of VIs you create to Recommended by default. Set a terminal setting to required only if the VI must have the input or output to runproperly. Refer to the Read File function located on the Functions>>All Functions>>File I/O palette for examples of required, recommended, and optional inputs andoutputs.