Question

Please can someone write me this program head.

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

Answer 1

It is basically a header file that also includes every standard library and stl include file. So if we #include <bits/stdc++.h> in a C++ program then there is no need to include any other header files.

Its just a header file which also includes all other standard libraries and stl header files. I myself personally use it to avoid extra #includes and compiler errors which may sometimes arise due to missing header files. However, it includes too much stuff which is mostly not used at all and also adds to compilation time. Thus, also executable file created using bits/stdc++.h has slightly higher size than without it, although difference is negligible.
you can compile below two codes and compare the size of the two executables.

#include<bits/stdc++.h>

using namespace std;

int main() {

               int x = 0;

               cout << x;

               return 0;

}

#include<iostream>

using namespace std;

int main() {

               int x = 0;

               cout << x;

               return 0;

}