OMNeT++: "Error in module (cModule) (id=1) during network setup..." Solution

Problem:

Frame title: Confirm
Frame content:
Error in module (cModule) "network name in ned file" (id=1) during network setup: Class "class name in cc file and simple name in ned file" not found -- perhaps its code was not linked in, or the class wasn't registered with Register_Class(), or in the case of modules and channels, with Define_Module()/Define_Channel().

Solution:

Right-click the project > select Build Project
In the console frame, you should get the following successful message: 12:34:56 Build Finished (took 5s.864ms)

Right-click the project > Run As > OMNeT++ Simulation

How to learn and interact with Mathematics on the browser using GeoGebra?

-- Browse to
http://app.geogebra.org/
-- Click on the Algebra link
--  On the left input textfield, type the following and then hit the enter key:
---- c =1
---- m = 2
---- y=mx + c
-- Click on "Toolbar > Angle of two lines with alpha icon > Slope". Click on the line to view the slope in triangle form
-- Go to the slider, drag to the left or drag to the right to change the c or m values
-- Other than Algebra section, try other Mathematics sections like Geometry, Spreadsheet, CAS, 3D Graphics, and Probability

An example from the above steps:

 
References
-- Animation: Move a Point, https://www.geogebra.org/m/n5ddtD86
-- Draw two functions in one graph with restricted domains, https://www.geogebra.org/m/GXC4GVEE