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National Instruments Corporation
9-1
9
Creating VIs
This chapter introduces the basic concepts of virtual instruments and
provides activities that explain the following:
•
How to create the icon and connector
•
How to use a VI as a subVI
What is a Virtual Instrument?
A virtual instrument (VI) is a program in the graphical programming
language G. Virtual instrument front panels often have a user interface
similar to physical instruments. G also has built-in functions that are similar
to VIs, but do not have front panels or block diagrams as VIs do. Function
icons always have a yellow background.
How Do You Build a VI?
One of the keys to creating BridgeVIEW applications is understanding and
using the hierarchical nature of the VI. After you create a VI, you can use
it as a subVI in the block diagram of a higher-level VI.
VI Hierarchy
When you create an application, you start at the top-level VI and define the
inputs and outputs for the application. Then, you construct subVIs to
perform the necessary operations on the data as it flows through the block
diagram. If a block diagram has a large number of icons, group them into a
lower-level VI to maintain the simplicity of the block diagram. This
modular approach makes applications easy to debug, understand, and
maintain.
As with other applications, you can save your VI to a file in a regular
directory. With G, you also can save multiple VIs in a single file called a
VI library.
Saving VIs as individual files is more effective than using VI libraries
because you can copy, rename, and delete files more easily than if you are
