Check Unit Matrix

Unit Matrix : An unit matrix is a diagonal matrix whose elements in the diagonal are all ones.
eg
                                         1 0 0 0
                                         0 1 0 0
                                         0 0 1 0
                                         0 0 0 1

#include<iostream.h>

#include<conio.h>

void main()
{
int mat[10][10];
cout<< "\n Enter dimension of square matrix;";
int n;
cin>>n;
cout<< "\n Enter the elements for the matrix :";

for(int i=0; i< n ; i++)
 for (int j = 0; j< n ; j++)
 { cout<<"\n Element for positon : " << i+1 << " , " << j+1 << ":"; cin>> mat[i][j];
}

int flag = 0;
for(int i=0; i< n ; i++)
for (int j = 0; j< n ; j++)
 { if(i == j)
     if(mat[i][j] ! = 1 )
            { flag = 1;
              break; }
 if(i != j)
    if(mat[i][j] ! = 0)
       { flag = 1; break; }
 }

if(flag == 0)
    cout<< "\n An UNIT Matrix .";
else
  cout<<"\n Not an UNIT matrix.";

cout<<"\n\n Matrix :";
for(int i=0; i< n ; i++)
{
for (int j = 0; j< n ; j++)
cout<< mat[i][j] << " ";
cout<< endl;
}
getch();

}