Still can't use a function defined in a separate .cpp file

Question

I've been searching through questions on this for hours, and it just isn't working for some reason, so sorry if there's already an answer and I just didn't understand it.

I'm doing a course on C++, and I've gotten to classes. As practice, he started by just calling a simple function that was defined in a separate .cpp file to show how a class would work later on. See code below:

//main.cpp
#include <iostream>
#include "Cat.h"
using namespace std;

int main() {
    speak();
    return 0;
}

============================

//Cat.cpp
#include <iostream>
#include "Cat.h"
using namespace std;

void speak() {
    cout << "Meow" << endl;
}

================================

//Cat.h
#ifndef CAT_H_
#define CAT_H_

void speak();

#endif //CAT_H_

I've triple checked everything I could think of. They're in the same directory and I'm cross-referencing everything exactly as he did. I expect it to output "Meow" in the console, but if I call the speak() function in main.cpp, I still just get an empty function, despite it being defined in class.cpp. I don't know what I'm missing, and it's quite frustrating. Is is because of my compiler? I'm using Visual Studio IDE.

Edits: Used the wrong commented name

I'm using the built-in Visual Studio IDE's "Build" and "Compile" options. I'm not running the compilation using Linux commands or anything else.

@273K Here is the screenshot of my 3 VS files: https://i.stack.imgur.com/9tbw8.png

Answer 1

The problem is that you are including Cat.h but named your header class.h instead of Cat.h.

To solve this rename the files from class.h and class.cpp to Cat.h and Cat.cpp respectively, as shown below

Cat.h

#ifndef CAT_H_
#define CAT_H_

void speak();

#endif //CAT_H_

Cat.cpp

#include <iostream>
#include "Cat.h"
using namespace std;

void speak() {
    cout << "Meow" << endl;
}

main.cpp

#include <iostream>
#include "Cat.h"
using namespace std;

int main() {
    speak();
    return 0;
}

Working demo

Answer 2

Thanks to @273K for the solution:

In the screenshot, the wrong project was "selected" in the solution explorer, so it was running the wrong project code.

I fixed it by right-clicking the project I wanted and clicking "Set as StartUp Project"

Before: https://i.stack.imgur.com/na0nF.png

After: https://i.stack.imgur.com/EJMLq.png