# Programming Tutorials

## Matrix using nested for loops in C++

By: Ignatius Printer Friendly Format

This simple C++ program illustrates the use of three nested for loops. The program multiplies matrix x and y and stores the resulting matrix product xy in matrix z. Both x and y must be compatible for multiplication that means, the number of columns of x must be equal to the number of rows of y.

```#include <iostream> using namespace std; #define  m  3 #define  c  2 #define  n  4 int main() {      int i, j, k;      // first matrix...      int x[m][c] = {{1,2},{3,4},{5,6}};      // second matrix...      int y[c][n] = {{7,8,9,10},{11,12,13,14}};      // for storing the matrix product result...      int z[m][n];      for(i=0; i<m; i++)             for(j=0; j<n; j++)             {                    z[i][j] = 0;                    for(k=0; k<c; k++)                    // same as z[i][j] = z[i][j] + x[i][k] * y[k][j];                    z[i][j] += x[i][k] * y[k][j];             }      cout<<"\nMultiply matrix x and matrix y,";      cout<<"\nThen store the result in matrix z.";      cout<<"\nMatrix x is 3x2, and matrix y is 2x4,";      cout<<"\nso, the result, z should be matrix 3x4\n";      cout<<"\nThe matrix product is:  \n";      for (i=0; i<m; i++)      {             cout<<"\n";             for(j=0; j<n; j++)               // display the result...               cout<<"   "<<z[i][j];      }      cout<<endl;      return 0; } ```

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