Definition: A function is a routine that returns a value when it executes.
It can be passed and it can return a value. Functions that are part of a class are usually called methods.
You can code your own functions or use built-in functions provided by Delphi RTL (run time library).
Examples:
function YearsOld(const BirthYear:integer): integer;
var
Year, Month, Day : Word;
begin
DecodeDate(Date, Year, Month, Day) ;
Result := Year - BirthYear;
end;
