## Introduction

I have used CodeBlocks compiler for debugging purpose. But you can use any C++ programming language compiler as per your availability.

#include <iostream> using namespace std; int main () { static int array[10][10]; int i, j, m, n, a; cout<<"Enter the order of the matix \n"; cin>>m; cin>>n; if (m == n) { cout<<"Enter the co-efficients of the matrix\n"; for (i = 0; i < m; ++i) { for (j = 0; j < n; ++j) { cin>>array[i][j]; } } cout<<"The given matrix is \n"; for (i = 0; i < m; ++i) { for (j = 0; j < n; ++j) { cout<<" "<<array[i][j]; } cout<<"\n"; } for (i = 0; i < m; ++i) { a = array[i][i]; array[i][i] = array[i][m - i - 1]; array[i][m - i - 1] = a; } cout<<"The matrix after changing the \n"; cout<<"main diagonal & secondary diagonal\n"; for (i = 0; i < m; ++i) { for (j = 0; j < n; ++j) { cout<<" "<<array[i][j]; } cout<<"\n"; } } else cout<<"The given order is not square matrix\n"; }