Finally got around to learning C++ but thats the warning I got from just putting in a Hello World program with <iostream.h> for a header:

backward_warning.h:32 #warning This file includes at least one deprecated or antiquated header. Please consider using one of the 32 headers found in section 17.4.1.2 of the C++ standard. Examples include substituting the <X> header for the <X.h> header for C++ includes, or <sstream> instead of the deprecated header <strstream.h>.

So I looked around and found that I should replace it with <iostream>, and thus these errors come up and the program no longer works

[Warning] In function `int main()':
4 ` cout' undeclared (first use this function)
(Each undeclared identifier is reported only once for each function it appears)
4 ` endl' undeclared (first use this function)
Code:
#include <iostream>
int main()
{
cout<<"Hello World"<<endl;
return 0;
}
I also tried it in this program
Code:
#include <iostream> 
int main() 
{ 
int thisisanumber; 
cout<<"Please enter a number:";
cin>>thisisanumber; 
cout<<"You entered: "<<thisisanumber;
return 0; 
}
it didn't run and had errors really similar to the hello world program except now its saying cout and cin is undeclared, but it works with iostream.h but the warning with the use of iostream.h came up again

And I have no clue what the errors mean
Also could someone explain to me what main does? I know that int main is declaring function main to return an integer but...what does that mean/do? I think return 0 just ends the program but is there a way to just leave the screen? I always have to add in an extra cin line so I can see if the last line of code actually worked