Getting input from file

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C++14

Hi guys, I've been working on a project and I'm having problems with the very beginning of it. I would appreciate any help.

So in this task, I should get my input from a file and from what I've learned I can do that using ifstream. I wrote a condition that if the file didn't open send me an error message.
and my problem is, it doesn't work and I keep getting the error message and it seems like it can't open the file and I can't find out why it won't open the file.

///////////////////////// my header file
#ifndef header_h
#define header_h


#include <iostream>
#include <fstream>
#include <vector>
#include <string>

using namespace std;

struct cam{
    string  name;
    string post;
    int age;
    int salary;
};

void data_input(string fn1, vector<cam> & W);         /*input data from our input file*/
#endif
/////////////////////////


/////////////////////////the main
#include <iostream>
#include <fstream>
#include "header.h"
using namespace std;

string inputfile="input.txt";
string outfile="output.txt";
vector<cam> employee_details;

int main()
{
    data_input(inputfile, employee_details);
    return 0;
}
/////////////////////////


/////////////////////////this the cpp file 
#include <stdio.h>
#include <iostream>
#include <vector>
#include <fstream>
#include "header.h"

using namespace std;

void data_input(string fn1, vector<cam> &W){
    string tmp;
    ifstream f1( fn1.c_str() );
   
    if( f1.is_open() )
    {
        while( f1.good() ))
        {
            //reading names
            getline (f1,tmp,';');
            cam tmp_cam;
            tmp_cam.name=tmp;
            W.push_back(tmp_cam);
            
            //reading the ages
            getline(f1,tmp,';');
            W.back().age = atoi( tmp.c_str() );
            
            //reading the ranks
            getline (f1,tmp,';');
            W.back().post = tmp;
            
            //reading the salaries
            getline (f1,tmp,';');
            W.back().salary = atoi( tmp.c_str() );
            
        }
      
        f1.close();
    }
    else
    {
        cout << "Error to open the file" <<  endl;
    }
    
}
/////////////////////////

What I have tried:

every thing I could find on the net but I feel I'm missing something really small that's why it came to my mind why not sharing it here and see it from different views