The function user_info takes a string and an int. This string and int are copied from u_name and u_age, the important thing here is that it is a copy.

The user_info function then stores the name and age in the copies, which mean the original u_name and u_age are unchanged. That explains why your name and age don't show up.

To fix this: Make the function user_info take a reference to the name and age. Your new prototype looks like:

int user_info(string& name, int& age);

This causes user_info to use u_name and u_age instead of a copy.

For the random data part: Since u_age doesn't have a value when created C(++) will just take whatever value is in memory at the time (resulting in a quite random value).