Structures
Owning Palette: Programming VIs and Functions
Requires: Base Package. 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 Object | Description |
|---|---|
| Array Index / Replace Elements | Right-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 Subarrays | Split 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 Structure | Has one or more subdiagrams, or cases, exactly one of which executes when the structure executes. The value wired to the selector terminal determines which case to execute and can be Boolean, string, integer, enumerated type, or error cluster. Right-click the structure border to add or delete cases. Use the Labeling tool to enter value(s) in the case selector label and configure the value(s) handled by each case. |
| Conditional Disable Structure | Has 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 Element | Accepts a 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. Right-click the border of an In Place Element structure and select Add Data Value Reference Read / Write Element from the shortcut menu to place this border node on the In Place Element structure. You cannot find these border nodes in the palette search or quick drop search. |
| Diagram Disable Structure | Has 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 Structure | Has one or more subdiagrams, or event cases, exactly one of which executes when the structure executes. The Event structure waits until an event happens, then executes the appropriate case to handle that event. The Time output responds to the Control event you use. Right-click the structure border to add new event cases and configure which events to handle. Wire a value to the Timeout terminal at the top left of the Event structure to specify the number of milliseconds the Event structure should wait for an event to occur. The default is –1, indicating never to time out. |
| Feedback Node | Stores data from one VI execution or loop iteration to the next. |
| Flat Sequence Structure | Consists 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. |
| For Loop | Executes 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 Node | Evaluates 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 Variable | Use global variables to access and pass data among several VIs. |
| In Place Element Structure | Controls 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 Element | Right-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 Node | Adds C code or assembly code to the block diagram. |
| Local Variable | Use local variables to read or write to one of the controls or indicators on the front panel of a VI. |
| MathScript Node | Executes 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. |
| Shared Variable | Represents 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. |
| Stacked Sequence Structure | Consists of one or more subdiagrams, or frames, that execute sequentially. Right-click the structure border to add and delete frames or to create sequence locals to pass data between frames. Use the Stacked Sequence structure to ensure a subdiagram executes before or after another subdiagram. |
| Unbundle / Bundle Elements | Right-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 To / From Element | Right-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 Elements | Right-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 Loop | Repeats the subdiagram inside it until the conditional terminal, an input terminal, receives a particular Boolean value. The Boolean value depends on the continuation behavior of the While Loop. Right-click the conditional terminal and select Stop if True or Continue if True from the shortcut menu. You also can wire an error cluster to the conditional terminal, right-click the terminal, and select Stop on Error or Continue while Error from the shortcut menu. The While Loop always executes at least once. |
| Subpalette | Description |
|---|---|
| Decorations | Use 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 VIs | Use the Timed Loop VIs to create and manipulate timing sources for a Timed Loop. |
| Timed Structures and VIs | Use 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. |
Example
Refer to the labview\examples\general\structs.llb for examples of using the Structures.