Uses a Matrix class to show a way to add, subtract, and multiply square matrices.

matrixclass.cpp

#include<iostream>
#include<conio.h>
#include<iomanip>

using namespace std;

const int ROW = 5;
const int COL = 5;

class matrix
{
	int a[ROW][COL];
	int row;
	int col;
public:
	matrix() : row(0), col(0)
	{}
	void read(int r, int c, matrix m1, matrix m2);
	void display();
	matrix add(matrix m1, matrix m2);
	matrix subtract(matrix m1, matrix m2);
	matrix multiply(matrix m1, matrix m2);
};

void matrix::read(int r, int c, matrix m1, matrix m2)
{
	row = r;
	col = c;

	for (int i = 0; i < r; i++)
	{
		for (int j = 0; j < c; j++)
		{
			cout << "A[" << i << "][" << j << "] : ";
			cin >> a[i][j];
		}
	}

	for (int i = 0; i < m1.row; i++)
	{
		for (int j = 0; j < m2.col; j++)
		{
			if (m1.a[i][j] != m2.a[i][j])
			{
				cout << "These matrices are not squares.\n"
					<< "Please run the program again.\n";
				break;
			}
		}
	}
}

void matrix::display()
{
	for (int i = 0; i < row; i++)
	{
		for (int j = 0; j < col; j++)
			cout << setw(4) << a[i][j];
		cout << endl;
	}
}

matrix matrix::add(matrix m1, matrix m2)
{
	matrix temp;
	temp.row = m1.row;
	temp.col = m2.col;

	for (int i = 0; i < temp.row; i++)
	{
		for (int j = 0; j < temp.col; j++)
		{
			temp.a[i][j] = m1.a[i][j] + m2.a[i][j];
		}
	}

	return temp;
}

matrix matrix::subtract(matrix m1, matrix m2)
{
	matrix temp;
	temp.row = m1.row;
	temp.col = m2.col;

	for (int i = 0; i < temp.row; i++)
	{
		for (int j = 0; j < temp.col; j++)
		{
			temp.a[i][j] = m1.a[i][j] - m2.a[i][j];
		}
	}

	return temp;
}

matrix matrix::multiply(matrix m1, matrix m2)
{
	matrix temp;
	temp.row = m1.row;
	temp.col = m2.col;

	for (int i = 0; i < temp.row; i++)
	{
		for (int j = 0; j < temp.col; j++)
		{
			for (int k = 0; k < temp.col; k++)
			{
				temp.a[i][j] = 0;
				temp.a[i][j] = temp.a[i][j] + (m1.a[i][k] * m2.a[k][j]);
			}
		}
	}

	return temp;
}

int main()
{
	matrix m1, m2, m3, m4, m5, m6, m7, m8;
	int r1, c1;
	cout << "Enter the order of first matrix: ";
	cin >> r1 >> c1;
	int r2, c2;
	cout << "Enter the order of second matrix: ";
	cin >> r2 >> c2;

	if (r1 != r2 && c1 != c2)
	{
		cout << "This matrix is not a square.\n"
			<< "Please try again.\n";
	}
	else
	{
		cout << "Enter elements of first matrix:\n";
		m1.read(r1, c1, m1, m2);
		cout << "Enter elements of second matrix:\n";
		m2.read(r2, c2, m1, m2);

		m4 = m3.add(m1, m2);
		cout << "Added matrix is:\n";
		m4.display();
		m6 = m5.subtract(m1, m2);
		cout << "Subtracted matrix is:\n";
		m6.display();
		m8 = m7.multiply(m1, m2);
		cout << "Resultant matrix is:\n";
		m8.display();
	}

	system("pause");
	return 0;
}