Structures

LabVIEW 2018 Help


Edition Date: March 2018
Part Number: 371361R-01
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Owning Palette: Programming VIs and Functions

Requires: Base Development System. This topic might not match its corresponding palette in LabVIEW depending on your operating system, licensed product(s), and target.

Use the structures to build VIs.

Palette ObjectDescription
Array Index / Replace ElementsRight-click the border of an In Place Element structure and select the Add Array Index / Replace Elements option from the shortcut menu to place this border node on the In Place Element structure.
Array Split / Replace SubarraysSplit an array into subarrays along a dimension you specify and operate on the subarrays in place within the structure. Right-click the border of an In Place Element structure and select the Add Array Split / Replace Subarrays option from the shortcut menu to place this border node on the In Place Element structure.
Case StructureContains one or more subdiagrams, or cases, exactly one of which executes when the structure executes. The value wired to the case selector determines which case to execute.
Conditional Disable StructureHas one or more subdiagrams, exactly one of which LabVIEW uses for the duration of execution, depending on the configuration of the conditions of the subdiagram. Use this structure when you want to disable specific sections of code on the block diagram based on some user-defined condition. Right-click the structure border to add or delete a subdiagram. When you add a subdiagram or right-click the structure border and select Edit Condition For This Subdiagram from the shortcut menu, you can configure conditions in the Configure Condition dialog box.
Data Value Reference Read / Write ElementAccepts a data value reference or an external data value reference as an input, allows you to operate on the data within the In Place Element structure, and replaces that data in the original memory space.

You can enable read-only access to the data value reference by right-clicking the border node on the right of the structure and selecting Allow Parallel Read-only Access. When the border node on the right is unwired, LabVIEW allows multiple, concurrent read-only operations and does not modify the data value reference.
Diagram Disable StructureHas one or more subdiagrams, or cases, of which only the Enabled subdiagram executes. Use the Diagram Disable structure to disable a section of the block diagram.
Event StructureWaits until an event occurs, then executes the appropriate case to handle that event. The Event structure has one or more subdiagrams, or event cases, exactly one of which executes when the structure executes to handle an event. This structure can time out while waiting for notification of an event. Wire a value to the Timeout terminal at the top left of the Event structure to specify the number of milliseconds the Event structure waits for an event. The default is -1, which indicates never to time out.
Feedback NodeStores data from one VI execution or loop iteration to the next.
Flat Sequence StructureConsists of one or more subdiagrams, or frames, that execute sequentially. Use the Flat Sequence structure to ensure that a subdiagram executes before or after another subdiagram.

Data flow for the Flat Sequence structure differs from data flow for other structures. Frames in a Flat Sequence structure execute from left to right and when all data values wired to a frame are available. The data leaves each frame as the frame finishes executing. This means the input of one frame can depend on the output of another frame.
For LoopExecutes its subdiagram n times, where n is the value wired to the count (N) terminal. The iteration (i) terminal provides the current loop iteration count, which ranges from 0 to n-1.
Formula NodeEvaluates mathematical formulas and expressions similar to C on the block diagram. The following built-in functions are allowed in formulas: abs, acos, acosh, asin, asinh, atan, atan2, atanh, ceil, cos, cosh, cot, csc, exp, expm1, floor, getexp, getman, int, intrz, ln, lnp1, log, log2, max, min, mod, pow, rand, rem, sec, sign, sin, sinc, sinh, sizeOfDim, sqrt, tan, tanh. There are some differences between the parser in the Mathematics VIs and the Formula Node.
Global VariableUse global variables to access and pass data among several VIs.
In Place Element StructureControls how the LabVIEW compiler performs certain operations and, in some cases, increases memory and VI efficiency. Use the In Place Element structure when you operate on a data element within an array, cluster, variant, or waveform without requiring the LabVIEW compiler to copy data values and maintain those values in memory. You also can use this structure to operate on any data type that you want to maintain within the same data space in memory. Right-click the border of the structure and select the border node that matches the operation you want to perform.
In Place In / Out ElementRight-click the border of an In Place Element structure and select the Add In Place In / Out Element option from the shortcut menu to place this border node on the In Place Element structure.
Inline C NodeAdds C code or assembly code to the block diagram.
Local VariableUse local variables to read or write to one of the controls or indicators on the front panel of a VI.
MathScript NodeExecutes LabVIEW MathScripts and your other text-based scripts using the MathScript RT Module engine. You can use the MathScript Node to evaluate scripts that you create in the LabVIEW MathScript Window.

If a MathScript Node contains a warning glyph, LabVIEW operates with slower run-time performance for the node. You can modify your script to remove the warning glyph from the MathScript Node and improve run-time performance.
Shared VariableRepresents a shared variable on the block diagram. To bind a Shared Variable node to a shared variable from the active project, add a Shared Variable node to the block diagram and double-click or right-click the node and select Select Variable»Browse from the shortcut menu to display the Browse for Variable dialog box. You also can drag a shared variable from the Project Explorer window onto the block diagram of a VI in the same project to create a Shared Variable node.
Type Specialization StructureHas one or more subdiagrams, exactly one of which LabVIEW compiles and executes, depending on the order and the compilation result of the subdiagram. LabVIEW declines subdiagrams in order if they have syntax errors. LabVIEW accepts the first subdiagram that does not have syntax errors and ignores the remaining subdiagrams. If all subdiagrams have syntax errors, this structure accepts the last subdiagram.

Use this structure to customize sections of code in a malleable VI (.vim) for specific data types. You also can use this structure in conjunction with the Assert Type VIs and function to force a malleable VI to accept only a subset of the acceptable data types.
Unbundle / Bundle ElementsRight-click the border of an In Place Element structure and select the Add Unbundle / Bundle Elements option from the shortcut menu to place this border node on the In Place Element structure.
Variant Attribute Get / ReplaceRight-click the border of an In Place Element structure and select the Add Variant Attribute Get / Replace option from the shortcut menu to place this border node on the In Place Element structure.
Variant To / From ElementRight-click the border of an In Place Element structure and select the Add Variant To / From Element option from the shortcut menu to place this border node on the In Place Element structure.
Waveform Unbundle / Bundle ElementsRight-click the border of an In Place Element structure and select the Add Waveform Unbundle / Bundle Elements option from the shortcut menu to place this border node on the In Place Element structure.
While LoopRepeats the code within its subdiagram until a specific condition occurs. A While Loop always executes at least one time.


SubpaletteDescription
DecorationsUse the decorations located on the Decorations palette to group or separate objects on a block diagram with boxes, lines, or arrows. These objects are for decoration only and do not modify data.
Timed Loop VIsUse the Timed Loop VIs to create and manipulate timing sources for a Timed Loop.
Timed Structures and VIsUse the Timed Structures and VIs to control the rate and priority at which a timed structure executes its subdiagram, synchronize the start time of timed structures, create timing sources, and establish a hierarchy of timing sources.

Related Information

Loops and Other Structures

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