What is return value and what is its use?

Answer 1

AnKuR, from a mathematical perspective on functions, the return value is the result the function calculates.
In programming these return values can be empty (see "void"). If a return value is empty, the function is either empty or it has only side effects (no modification of parameters, but e.g. console output, modification of a global variable or memory that is not parameters in general).
Oftentimes, the return value is determined by convention. The main function is a good example: returning 0 means "no error occurred in the program", all other (positive) values are codes to signal the kind of error that occured.

Answer 2

main() returns an int type to operating system.therefore, evry main() shud end with a return(0) statement; otherwise a warning or an error might occur.note that default return type for all functions in c++ us int.
hope now u ll understand the concept of return.