Need to call a function in C, that function has been defined in C++ and declared in customized header file, but facing <iostream> error

I'm new to this topic, so i started with basic program of printing 10 numbers.
The function has been defined in C++ and declared in my customized header file, now i want to access this function in C file. I have created the files, but i'm facing fatal error: iostream: No such file or directory
Please let me know where i'm going wrong. I have attached the programs below:
C++ code:

#include <iostream>
#include "my_header.h"

// Function definition
void printNumbers() {
    for (int i = 1; i <= 10; i++) {
        std::cout << i << " ";
    }
    std::cout << std::endl;
    int main()
    {
        return 0;
    }
}

Header file:

#include "my_cpp.cpp"

#ifndef NUMBERS_H
#define NUMBERS_H

// Function declaration
void printNumbers();

#endif

C code:

#include <stdio.h>
#include "my_header.h"
int main() {
    // Call the function defined in C++
    printNumbers();
    return 0;
}

Thanks in advance.

The mistake here is that you have included a source file in a header file

#include "my_cpp.cpp"

The results in your C compiler seeing your C++ code and hence you get the error you get.

C and C++ operate on a model of separate compilation, which that each C or C++ source file must be compiled independently. A source file and the header files it includes is called a translation unit.

How you compile each source file separately and then link them together depends on what compiler/IDE you are using, but using #include is not the way to do this.

Also you have other problems to do with mixing C and C++. It's not clear why you are doing this, it's a strange thing for a newbie programmer to be doing. But if you really want to you need to make the following changes. These changes are to give your C++ function C linkage, which is necessary to call a C++ function from C.

Change your header file like this

#ifndef NUMBERS_H
#define NUMBERS_H

#ifdef __cplusplus
extern "C" {
#endif

// Function declaration
void printNumbers();

#ifdef __cplusplus
}
#endif

#endif

The extern "C" part gives your function C linkage, but this code is only legal in C++. Therefore it has to be wrapped in #ifdef __cplusplus to make sure that this is only seen by the C++ compiler.

Additionally you can define your function with the same linkage in your C++ source file

// Function definition
extern "C" void printNumbers() {

though this is not really necessary, the declaration is sufficient as long as you follow best practise and include the header file in the source file.