About Use of #include Preprocessor Directive in C++ - c++

Question

I stumble on the following compilation error in C++ with g++ compiler:
error on line line 1 with message:
invalid preprocessing directive #a
(with a caret above the character a) which is followed by another,probably consequent, error on line 4 with message:
cout was not declared in this scope.
The editor i am using is Code blocks 10.05 with mingw.I tried removing .h extension from the iostream file include statement;switching among different File encoding options;and replacing the angular bracket with single quotes and double quotes as well.i am stuck on it.Pardon if it is a duplicate(although i went through several already asked questions in relevance).
The following code illustrates the problem:
#‪include ‬<iostream.h>
int main()
{
cout<< "abc"+8;
cout<< "def"+4;
cout<< "ha";
return 0;
}

Answer 1

cout exists within the namespace std
So either
#‪include‬<iostream>
//...
std::cout << "abc" << 8;
//...
or
#‪include‬<iostream>
using namespace std;
//...
or
#‪include‬<iostream>
using std::cout;
//...
I tend to prefer the 1st if I'm only using it once or twice, The second if I'm using a lot of different pieces from a namespace (and only in a cpp file), or the third if I'm only using a piece or 2 from a namespace but using the same couple many times.
Additionally as stated in the comments, don't use the 2nd one in headers. See: "using namespace" in c++ headers
Also, you have an invalid character in your #include. You can see it in a hex editor or Note how stackoverflow doesn't highlight them the same:
#‪include‬<iostream>
#include<iostream>
Fully working code:
#include<iostream>
using std::cout;
int main()
{
cout << "abc" << 8;
cout << "def" << 4;
cout << "ha";
return 0;
}
Produces the following output abc8def4ha after I corrected for trying to add 8 to a char*

Answer 2

You have to use std::cout, which means that the "cout" keyword is part of the standard library.

Answer 3

The "invalid directive" error is caused by some invisible Unicode characters in the #include directive; perhaps you copied this from a website that embedded some formatting characters in the code. They can be seen in the question, if you look at the source in a hex editor. That error should be fixed by deleting and retyping the #include line.
You'll probably have other errors, since the code is fifteen years out of date; most modern compilers don't provide pre-standard libraries. These days, the standard library headers don't have a .h extension:
#include <iostream>
and nearly all the names they declare are scoped inside the std namespace:
std::cout << "ha";
Finally, "abc"+8 doesn't do anything sensible. The string literal is an array of four characters, and +8 tries to give you a pointer to the ninth character, which doesn't exist. The result is undefined behaviour.
If you want to print "abc" followed by "8", then you want:
std::cout << "abc" << 8;

Answer 4

Try using it like this:-
#‪include ‬<iostream>
using std :: cout;
cout is the part of std library

Answer 5

If you've got caret above a, try retyping your #include.
You might accidentally type alternative i which looks similar but has different code.
Suggestions about std:: are only relevant for the second error you're getting.
I also didn't fully understand what you were trying to achieve with "abc"+8.