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'cout' was not declared in this scope [FIXED]

C++

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In this article, we have explored the reason behind the compilation error "cout was not declared in this scope" and how to fix it.

Table of contents:

  1. Reason for error
  2. Fix 1: using namespace
  3. Fix 2: Scope resolution operator

The quick fix is to add the following line in your C++ code just after the include statements:

using namespace std;

Reason for error

While compiling a C++ code, you may get this compilation error:

'cout' was not declared in this scope

If you compile this C++ code, you will get this compilation error:

#include <iostream>

int main() {
    std::cout << "data" << std::endl;
    return 0;
}

Fix 1: using namespace

The easiest fix is to add the code line "using namespace std;" at the top of the code after include statements. This tells the compiler that functions like cout and endl are under the namespace std.

using namespace std;

Following is the complete working C++ code:

#include <iostream>
using namespace std;

int main() {
    cout << "data" << endl;
    return 0;
}

Fix 2: Scope resolution operator

An alternative fix is to add the namespace std with cout and endl using the scope resolution operator. Following are the required changes:

  • Replace "cout" with "std::cout"
  • Replace "endl" with "std::endl"

Following is the complete working C++ code:

#include <iostream>

int main() {
    std::cout << "data" << std::endl;
    return 0;
}

With the fixes in this article at OpenGenus, you must have solved this issue. Continue with your C++ development.

Geoffrey Ziskovin

Geoffrey Ziskovin

Geoffrey Ziskovin is an American Software Developer and Author with an experience of over 30 years. He started his career with Haskell and has interviewed over 700 candidates for Fortune 500 companies

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Improved & Reviewed by:


OpenGenus Foundation OpenGenus Foundation
'cout' was not declared in this scope [FIXED]
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