step function

[SAL2005]

Is there a step function in Labview module? I couldnt find it.

SAL

[Will.D]

There's a simulate signal express VI that you can use to simulate a square wave. 

Express->Input->Simulate Signal

[tst]

There are single-stepping buttons on the toolbar, but you should be aware that because of the

inherent parallel nature of LV code, it may be harder to follow. You can also place breakpoints (on your tools palette) and play the program in "slow motion" (Highlight Execution).

To learn more about LabVIEW, I suggest you try searching this site and google for LabVIEW tutorials. Here and here are a couple you can start with. You can also contact your local NI office and join one of their courses.
In addition, I suggest you read the LabVIEW style guide and the LabVIEW user manual (Help>>Search the LabVIEW Bookshelf).