The main function takes no parameters and returns a value

(See Listing 1.)

Every C++ program that runs in a stand-alone mode requires a function named main. 

Execution of the program begins and ends in the main function.

For simple programs at least, when the main function runs out of things to do, the program terminates.

Different formats can be used for the main function.

This format takes no parameters and returns a value of type int.