why cin.get work here??

[vkash]

In the first case, you use getline(). getline() processes input until a '\n'
is encountered. So after entering the year (followed by return), the '\n'
is still in the input stream buffer, so addess ends up empty (as you observed).

In the second case, you are using operator >> ... By default, operator >>
ignores whitespaces, so the fact that the '\n' is still in the input buffer
stream is not relevant.

so you mean if we get very next input by >>(after cin.getline) operator then no such probem will appear..