1.5) Your First C++ Program: Returning A Value From main

The int part of int main() means that the main function returns an int (integer) value to its caller - which, in this case, is the operating system environment that invoked the program.

This returned value is the program exit status. By convention, an exit status of 0 means that the program ran successfully; non-zero values can be used to indicate error of different kinds

Program exit status is available for use by an operating system shell:

• In the Linux bash shell, it is stored in the shell variable $?
• In the Windows command shell, it is stored in the variable errorlevel