Summary Virtual instruments (VIs) contain three main components-the front panel, the block diagram, and the icon and connector pane. The front panel is the user interface of a VI and specifies the inputs and displays the outputs of the VI. The block diagram contains the graphical source code composed of nodes, terminals, and wires. Use the Tools palette to create, modify, and debug VIs. Press the Shift key and right-click to display a temporary version of the Tools palette at the location of the cursor. Use the Controls palette to place controls and indicators on the front panel. Right-click an open space on the front panel to display the Controls palette. Use the Functions palette to place VIs and functions on the block diagram. Right-click an open space on the block diagram to display the Functions palette. Use the Search button on the Controls and Functions palettes to search for controls, VIs, and functions. All LabVIEW objects and empty space on the front panel and block diagram have associated shortcut menus, which you access by right-clicking an object, the front panel, or the block diagram. Use the Help menu to display the

Context
	  Help

window and the LabVIEW Help, which describes most palettes, menus, tools, VIs, functions, and features. Select Help>>Search the LabVIEW Bookshelf to display the LabVIEW Bookshelf, which you can use to search PDF versions of all the LabVIEW manuals and Application Notes. You build the front panel with controls and indicators, which are the interactive input and output terminals of the VI, respectively. Control terminals have a thicker border than indicator terminals. To change a control to an indicator or to change an indicator to a control, right-click the object and select Change to Indicator or

Change to
	  Control

from the shortcut menu. The block diagram is composed of nodes, terminals, and wires. The broken Run button appears on the toolbar to indicate the VI is broken. Click the broken Run button to display the Error list window, which lists all the errors. Use execution highlighting, single-stepping, probes, and breakpoints to debug VIs by animating the flow of data through the block diagram.

Tips and Tricks

Operating Frequently used menu options have equivalent keyboard shortcuts. For example, to save a VI, you can select File>>Save or press the Ctrl-S keys. Common keyboard shortcuts include the following: Ctrl-R Runs a VI. Ctrl-E Toggles between the front panel and block diagram. Ctrl-H Toggles display of the Context Help window. Ctrl-B Removes all broken wires. Ctrl-F Finds VIs, globals, functions, text, or other objects loaded in memory or in a specified list of VIs. To increment or decrement numeric controls faster, use the Operating or Labeling tools to place the cursor in the control and press the Shift key while pressing the up or down arrow keys. You can disable the debugging tools to reduce memory requirements and to increase performance slightly. Select File>>VI Properties, select Execution from the top pull-down menu, and remove the checkmark from the Allow Debugging checkbox.

Wiring Click the Show Context Help Window button on the toolbar to display the Context Help window. Use the Context Help window to determine which terminals are required. Required terminals are bold, recommended connections are plain text, and optional connections are dimmed. Press the spacebar to toggle the wire direction. To move objects one pixel, press the arrow keys. To move objects several pixels, press the Shift key while you press the arrow keys. To cancel a wire you started, press the Esc key, right-click, or click the terminal where you started the wire. Use the tip strips that appear as you move the Wiring tool over terminals. Display the connector pane by right-clicking the node and selecting Visible Items>>Terminals from the shortcut menu. You can bend a wire by clicking to tack the wire down and moving the cursor in a perpendicular direction. To tack down a wire and break it, double-click.

1. Tack Down a Wire by Clicking, 2. Tack and Break the Wire by Double-clicking

Editing Use the following shortcuts to create constants, controls, and indicators: Right-click a function terminal and select Create>>Constant, Create>>Control, or Create>>Indicator from the shortcut menu. Drag controls and indicators from the front panel to the block diagram to create a constant. Drag constants from the block diagram to the front panel to create a control. To duplicate an object, press the Ctrl key while using the Positioning tool to click and drag a selection. To restrict an object's direction of movement horizontally or vertically, use the Positioning tool to select the object and press the Shift key while you move the object. To keep an object proportional to its original size as you resize it, press the Shift key while you drag the resizing handles or circles. To resize an object as you place it on the front panel, press the Ctrl key while you click to place the object and drag the resizing handles or circles. To replace nodes, right-click the node and select Replace from the shortcut menu. 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. 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 can select Browse>>This VI's SubVIs. After you type a label, press the Enter key to end text entry. To add items quickly to ring controls and Case structures, press the Shift-Enter keys after each item. Pressing Shift-Enter accepts the item and positions the cursor to add the next item. Refer to Making Decisions in a VI for more information about Case structures. To copy the color of one object and transfer it to a second object without using a color picker, use the Color Copy tool to click the object whose color you want to copy. Use the Coloring tool to click the object to which you want to apply the color. You also can copy the color of one object by using the Coloring tool and pressing the Ctrl key. Select Edit>>Undo if you make a mistake. To create more blank space on the block diagram, press the Ctrl key while you use the Positioning tool to draw a rectangle on the block diagram.

Debugging When single-stepping, use the following keyboard shortcuts: Ctrl-down arrow Steps into a node. Ctrl-right arrow Steps over a node. Ctrl-up arrow Steps out of a node.