C++ open input file failed

This is the beginning of the code i have and it keeps returning the "cannot open file" and i cannot see why...

Code:

#include <fstream> 
#include <cstdlib> 
#include <iostream> 
#include <iomanip> 
#include <math.h>

using namespace std; 

#define MAXD 100 

ifstream in_file; 
ofstream out_file;

void read_input(int& NJ, double COORD[MAXD][2], int& NS, int MSUP[MAXD][3], int& NMP, double EM[MAXD], int& NC, double CP[MAXD], int& NM, double MPRP[MAXD][4], int& NLJ, int JP[MAXD], double PJ[MAXD][2]);
void Struct_Stiffness(double KL[4][4], double L, double E, double A, double C, double S);

int main()
{
	int NJ, NS, NMP, NC, NM, NLJ;
	double COORD[MAXD][2]={0};
	int MSUP[MAXD][3]={0};
	double EM[MAXD]={0};
	double CP[MAXD]={0};
	double MPRP[MAXD][4]={0};
	int JP[MAXD]={0};
	double PJ[MAXD][2]={0};
	double Stiff[MAXD][MAXD]={0};

	int NP[4];
	
	int el=0;
	int i, j;
	
	in_file.open("input.txt");
	out_file.open("output.txt");
	
	
	if(in_file.fail()) 
	{ 
		cout << "The file cannot be opened." << endl; 
		exit(1); 
	} 	
	
	read_input(NJ, COORD, NS, MSUP, NMP, EM, NC, CP, NM, MPRP, NLJ, JP, PJ); 
	..................

 

It is in the working directory because when the output file is opened that is where it appears... sorry im quite new to this

 

I now realize that the program continues to run (loop) as well and i have to stop it manually... does this have something to do with it?