Cin is not a member of std in C++

Introduction

The std::cin function is a highly useful function that allows us to input user data from the console into our C++ program. However, we can often get errors from the compiler such as:

error: ‘cin’ is not a member of ‘std’

This error is pretty straight-forward to fix as we will see below.

Potential causes

The cin is not a member of std error could be caused by multiple reasons.

Fix #1: Add iostream to your depedencies

Essentially, the std::cin function needs to have access to the iostream module in order to be executed by the compiler.

Therefore, you must add the following #include header to the top of your code (in the include(s) part) such as:

#include <iostream> //Add this

int main() {
    int x;
    std::cin >> x;
    std::cout << "You wrote: " << x << std::endl;
    return 0;
}

The compiler should now recognize the std::cin function, thus fixing the cin is not a member of std error.

If the std error still persists, keep reading below.

Fix #2: Using namespace std

Note that we have previously typed: std::cin instead of cin. We can type “cin” only if we are declaring that we are using its namespace.

In other words, we would need to type “using namespace std” in the header if we only want to type cin (which is obviously shorter) instead of std::cin. For instance, we can have something like:

#include <iostream>
using namespace std; //Add this

int main() {
    int x;
    cin >> x;
    cout << "You wrote: " << x << endl;
    return 0;
}

It is okay to type std::cin without typing “using namespace std”. In fact, it is generally recommended to type the full std::cin function name (and therefore avoiding using namespace std) when working with multiple libraries because it can reduce future confusion.

However, if you still want to type “cin” instead of “std::cin”, then you need to add “using namespace std” to the header

References

Read more about the std::cin function here: https://www.cplusplus.com/reference/iostream/cin/