trying to write a code where I can enter a name and then it says hi, your_name?

Here is the code and codeblocks is saying cout was not declared in this scope. What does that mean?

Code:

---

#include <iostream>int
main()
{




cout<<"Please enter your name:\n";
string first_name;
cin>> first_name;
cout<<"Hello"<<first_name<<"!\n";


return 0;




}

---

cout, cin, and string belong to the std namespace, so instead of just writing cout, cin, or string, you're supposed to write std::cout, std::cin, and std::string e.g.,

Code:

---

#include <iostream>
#include <string>

int main()
{
    std::cout << "Please enter your name:\n";
    std::string first_name;
    std::cin >> first_name;
    std::cout << "Hello" << first_name << "!\n";
    return 0;
}

---

Notice that I placed the #include <string> for std::string. I also indented the code properly and removed blank lines that do not contribute to readability.

Because all three names are from the std namespace, you could also use a using directive within a local scope to bring them into scope and hence be able to use them without qualifying them with the namespace name, e.g.,

Code:

---

#include <iostream>
#include <string>

int main()
{
    using namespace std;
    cout << "Please enter your name:\n";
    string first_name;
    cin >> first_name;
    cout << "Hello" << first_name << "!\n";
    return 0;
}

---

Quote:

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Originally Posted by laserlight

cout, cin, and string belong to the std namespace, so instead of just writing cout, cin, or string, you're supposed to write std::cout, std::cin, and std::string e.g.,

Code:

---

#include <iostream>
#include <string>

int main()
{
    std::cout << "Please enter your name:\n";
    std::string first_name;
    std::cin >> first_name;
    std::cout << "Hello" << first_name << "!\n";
    return 0;
}

---

Notice that I placed the #include <string> for std::string. I also indented the code properly and removed blank lines that do not contribute to readability.

Because all three names are from the std namespace, you could also use a using directive within a local scope to bring them into scope and hence be able to use them without qualifying them with the namespace name, e.g.,

Code:

---

#include <iostream>
#include <string>

int main()
{
    using namespace std;
    cout << "Please enter your name:\n";
    string first_name;
    cin >> first_name;
    cout << "Hello" << first_name << "!\n";
    return 0;
}

---

---

Got a question for you. Deos that mean you only need to enter namespace std; once?

Quote:

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Originally Posted by solidusMGS

Deos that mean you only need to enter namespace std; once?

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Yes, within the scope in which it was used.

You can use it at file scope, but unless there are only a few functions, it usually is not a good idea because it means that all the names from all the standard headers included become injected into the global namespace throughout the file after the using directive.