This implies each VI can be easily tested before being embedded as a subroutine into a larger program. Thus a virtual instrument can be run as either a program, with the front panel serving as a user interface, or, when dropped as a node onto the block diagram, the front panel defines the inputs and outputs for the node through the connector pane. Nodes are connected to one another using wires, e.g., two controls and an indicator can be wired to the addition function so that the indicator displays the sum of the two controls. Collectively controls, indicators, structures, and functions will be referred to as nodes. The structures and functions are found on the Functions palette and can be placed on the back panel. The back panel also contains structures and functions which perform operations on controls and supply data to indicators. All of the objects placed on the front panel will appear on the back panel as terminals.
The back panel, which is a block diagram, contains the graphical source code. Indicators are outputs: they indicate, or display, the results based on the inputs given to the VI. Controls are inputs: they allow a user to supply information to the VI. The front panel is built using controls and indicators. The last is used to represent the VI in the block diagrams of other, calling VIs. Each VI has three components: a block diagram, a front panel, and a connector panel. LabVIEW programs-subroutines are termed virtual instruments (VIs). LabVIEW integrates the creation of user interfaces (termed front panels) into the development cycle. Multi-processing and multi-threading hardware is exploited automatically by the built-in scheduler, which multiplexes multiple OS threads over the nodes ready for execution. Since this might be the case for multiple nodes simultaneously, G can execute inherently in parallel. These wires propagate variables and any node can execute as soon as all its input data become available. Execution is determined by the structure of a graphical block diagram (the LabVIEW-source code) on which the programmer connects different function-nodes by drawing wires.
The programming language used in LabVIEW, named G, is a dataflow programming language. 5.4 Parallel execution and race conditions.
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