Earlier, you found that the main function returned a value and by default this value is zero. When your application finishes, you can return an error code back to the command line; this is so that you can use the executable in batch files and scripts, and use the value to control the flow within the script. Similarly, when you run an executable, you may pass parameters from the command line, which will affect how the executable will behave.
Run the simple application by typing the simple command on the command line. In Windows, the error code is obtained through the pseudo environment variable ERRORLEVEL, so obtain this value through the ECHO command:
C:\Beginning_C++\Chapter_01>simple ...
