# C++ : Multiply two Matrices by Passing Matrix to Function

Tutorial by:Manisha Dubey      Date: 2016-06-18 04:54:30

This program asks user to enter the size of the matrix (rows and columns) then, it asks the user to enter the elements of two matrices and finally it multiplies two matrix and displays the result. To perform this task three functions are made:

1. To take matrix elements from user
2. To multiply two matrix
3. To display the resultant matrix after multiplication

### Source Code to Multiply Matrix by Passing it to a Function

``````
#include <iostream>
using namespace std;
void take_data(int a[][10], int b[][10], int r1,int c1, int r2, int c2);
void multiplication(int a[][10],int b[][10],int mult[][10],int r1,int c1,int r2,int c2);
void display(int mult[][10], int r1, int c2);
int main()
{
int a[10][10], b[10][10], mult[10][10], r1, c1, r2, c2, i, j, k;
cout << "Enter rows and columns for first matrix: ";
cin >> r1 >> c1;
cout << "Enter rows and columns for second matrix: ";
cin >> r2 >> c2;

/* If colum of first matrix in not equal to row of second matrix, asking user to enter the size of matrix again. */

while (c1!=r2)
{
cout << "Error! column of first matrix not equal to row of second." << endl;
cout << "Enter rows and columns for first matrix: ";
cin >> r1 >> c1;
cout << "Enter rows and columns for second matrix: ";
cin >> r2 >> c2;
}
take_data(a,b,r1,c1,r2,c2);  /* Function to take matrices data */
multiplication(a,b,mult,r1,c1,r2,c2); /* Function to multiply two matrices. */
display(mult,r1,c2); /* Function to display resultant matrix after multiplication. */
return 0;
}

void take_data(int a[][10], int b[][10], int r1,int c1, int r2, int c2)
{
int i,j;
cout << endl << "Enter elements of matrix 1:" << endl;
for(i=0; i<r1; ++i)
for(j=0; j<c1; ++j)
{
cout << "Enter element a" << i+1 << j+1 << " : ";
cin >> a[i][j];
}

cout << endl << "Enter elements of matrix 2:" << endl;
for(i=0; i<r2; ++i)
for(j=0; j<c2; ++j)
{
cout << "Enter element b" << i+1 << j+1 << " : ";
cin >> b[i][j];
}
}

void multiplication(int a[][10],int b[][10],int mult[][10],int r1,int c1,int r2,int c2)
{
int i,j,k;
/* Initializing elements of matrix mult to 0.*/
for(i=0; i<r1; ++i)
for(j=0; j<c2; ++j)
{
mult[i][j]=0;
}
/* Multiplying matrix a and b and storing in array mult. */
for(i=0; i<r1; ++i)
for(j=0; j<c2; ++j)
for(k=0; k<c1; ++k)
{
mult[i][j]+=a[i][k]*b[k][j];
}
}

void display(int mult[][10], int r1, int c2)
{
int i, j;
cout << endl << "Output Matrix: " << endl;
for(i=0; i<r1; ++i)
for(j=0; j<c2; ++j)
{
cout << " " << mult[i][j];
if(j==c2-1)
cout << endl;
}
}``````

Output

```Enter rows and column for first matrix: 3
2
Enter rows and column for second matrix: 3
2
Error! column of first matrix not equal to row of second.

Enter rows and column for first matrix: 2
3
Enter rows and column for second matrix: 3
2

Enter elements of matrix 1:
Enter elements a11: 3
Enter elements a12: -2
Enter elements a13: 5
Enter elements a21: 3
Enter elements a22: 0
Enter elements a23: 4

Enter elements of matrix 2:
Enter elements b11: 2
Enter elements b12: 3
Enter elements b21: -9
Enter elements b22: 0
Enter elements b31: 0
Enter elements b32: 4

Output Matrix:
24 29

6  25
```

## C++

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