Assigning data from file to matrix C++

Array indices start at 0, not 1.

Here's a typical, robust, albeit not perfectly optimal general method for reading input: Read each line first, and then parse each line into tokens. Length checking can be added of course so that you don't attempt to read a file with billions of lines, but I leave that to you.

Note that we never explicitly call close(), since that's not needed.

#include <iostream>
#include <sstream>
#include <iterator>  // for istream_iterator
#include <string>    // for getline and string
#include <vector>    // for vector
#include <cstdlib>   // for exit

namespace
{
    void die(int code, char const * msg)
    {
        std::cerr << msg << std::endl;
        std::exit(code);
    }
}

int main()
{
    std::ifstream tm("TM.txt");

    if (!tm) { die(1, "Could not open file."); }

    std::vector<std::vector<int>> matrix;

    for (std::string line; std::getline(tm, line); )
    {
        std::istringstream iss(line);
        std::vector<int> row(2);

        if (!(iss >> row[0] >> row[1])) { die(1, "Invalid line!"); }

        matrix.push_back(row);
    }

    // done, now use matrix[i][j]
}

In C++11 you could add various small optimisations, but never mind about that now. In a more general setting, you could also remove the restriction that each row consist of only two elements and instead read as many as there are, possibly checking the final size:

std::vector<int> row(std::istream_iterator<int>(iss), std::istream_iterator<int>());
// check that row.size() has the desired value!

Finally, you might like to add a counter to the outer loop and abort if there are more lines than expected (e.g. 46 in your case), so that you can't be sabotaged by a huge input file.

Thanks @KerrekSB for your response. This level of C++ programming is quiet one step ahead of basic knowledge of C++. Nevertheless, I tried your suggestion and rewrite the code as is posted:

#include <stdlib.h>
#include <malloc.h>
#include <iostream>
#include <fstream>
#include <sstream>
#include <iterator>  // for istream_iterator
#include <string>    // for getline and string
#include <vector>    // for vector
#include <cstdlib>   // for exit

using namespace std;

namespace
{
    void die(int code, char const * msg)
    {
        std::cerr << msg << std::endl;
    std::exit(code);
    }
}

void AllocateMatrix(int **& A, int row, int col)
{
int i;
A = new int*[row];
for (i=0; i<col; i++)
    A[i] = new int[col];
}

void ReadData(int **& A, int row, int col) // read data from file
{  
int i,j,in;
ifstream REL1;
REL1.open ("REL");  // open file for reading                
for(i=0;i<row;i++)   // row loop
{
    REL1 >> in; // read data into matrix
    for(j=0;j<col;j++)  // column loop
    {
        A[i][j]=in;
    }
}
REL1.close(); // close the file                
}

void Display(int **& A, int row, int col) // display matrix
{ 
int i,j;
for(i=0;i<row;i++)
{
    for(j=0;j<col;j++)
    { 
        cout << A[i][j] << "\t ";  // display numbers
    }
}
cout <<endl;    
}

void Cero(int **& A, int row, int col) // display matrix
{
int i,j;
for(i=0;i<row;i++)
{
    for(j=0;j<col;j++)
    {
        A[i][j]=0;
    }
}   
}   

int main()
{
int tm,rowR,colR,rowM,colM,**A,**B; 

ifstream TM;
TM.open("TM");
TM >> tm;
TM.close();

rowR = 46; 
rowM = colM = tm;
colR = 2;

AllocateMatrix(A, rowM, colM);
AllocateMatrix(B, rowR, colR);
Cero(A, rowM, colM); 
//Display(A, rowM, colM);
//ReadData(B ,rowR, colR);


std::ifstream rel("REL");
if (!rel) { die(1, "Could not open file."); }
std::vector<std::vector<int> > matrix;
for (std::string line; std::getline(rel, line); )
{
    std::istringstream iss(line);
    std::vector<int> row(2);
    if (!(iss >> row[0] >> row[1])) { die(1, "Invalid line!"); }
    matrix.push_back(row);
}




Display(B, rowR, colR);
}

And when I execute it, it prompet :

Invalid line!