#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

//Define functions.
void input(ifstream& fin, char& fileName);

int main()
{
    ifstream fin;
    char fileName[20];
    input(fin, fileName);
    return 0;
}

void input(ifstream& fin, char& fileName)
{
    cout << "Input file name: ";
    cin >> fileName;
    fin.open(fileName);

    if(fin.fail())
    {
        cout << "The file:  " << fileName << " does not open." << endl;
        exit(1);
    }
    //return;
}

#include <iostream>
#include <fstream>
#include <cstdlib>
using namespace std;

//Define functions.
void input(ifstream& fin, string& fileName);

int main()
{
    ifstream fin;
    string fileName;
    input(fin, fileName);
    return 0;
}

void input(ifstream& fin, string& fileName)
{
    cout << "Input file name: ";
    cin >> fileName;
    fin.open(fileName.c_str());

    if(fin.fail())
    {
        cout << "The file:  " << fileName << " does not open." << endl;
        exit(1);
    }
    //return;
}

void input(ifstream *fin, char *fileName);

input(&fin, &fileName); // call