Some good websites to brush up DBMS and OS for interviews within 4-5 days ????

Have a coding round for job tommorow!
Feeling scared and nervous !!!!!!!!!!!!

Have a job interview in 4 days any tips on what all stuffs to focus on ?

Friend : Hey bro I made an awesome program which shows your future wife's name.

Me : Hey that sounds interesting, show me the source code bro !!

Friend shows the code :

#include <bits/stdc++.h>
using namespace std;

int main()
{
string first_name , last_name;

cout << "Enter your first name\n";
cin >> first_name ;

cout << "Enter your last name\n";
cin >> last_name ;

cout << "Your wife's name is " << "Mrs " << last_name << "\n";

}

Me : Dude you are gonna crack Google some day :P