An important feature of Prograph is that the editor and interpreter can run concurrently. Therefore, the user can pause a running application, modify the elements of the user interface, and resume the application with new functionality. The Application Builder is similar to the interface construction tools provided with other products such as Visual Basic. LabVIEW combines structured programming and data flow programming paradigms and embeds them in a graphical editing and execution system. It uses a virtual instrument metaphor in which a program is viewed as a hierarchy of instrument-like modules containing interactive front panels and block diagrams.
Arrows represent the flow of data between boxes.
In the boxgraph notation, boxes may be hierarchically nested and arrows may point from a box at any level in the hierarchy to another box at any other level, as long as no cycle is created in the boxgraph. STL uses the concept of consistency for program control, emulating an IF-THEN construct without the introduction of specific flow control ideas. A boxgraph becomes inconsistent when there is a conflict of some type among the data flowing into the box. Figure 2 shows an example arithmetic problem which is designed to give an answer only when two expressions are equal. STL provides a number of box types to perform arithmetic operations, iterations, higher order functions, and database construction.