Multiplication of two matrices in C

Program to multiply two matrices in C

Product of matrices can be done when the matrices are compatible with each other.
The matrices are said to be compatible with each other when the number of columns of first matrix is equal to number of rows of second matrix.
Thus, if the first matrix has n columns and second matrix has q rows ; then n = q is essential.
Thus, the elements can be multiplied using the following formula: C_i,j = Sum of ( A_i,j* B_i,k) ; where k = 1 to k < n.

Approach:

First we will take the number of rows and columns of each matrix as our input.
Next we validate if multiplication is possible, based upon number of the condition n = q; where n is number of column of first matrix and q is number of rows of second matrix.
Next, using the above mentioned formula we calculate the product of the matrices.
Here we are passing arrays between function as an input to next function.

Code:

#include <stdio.h>
void multiply(int arr1[5][5], int arr2[5][5], int, int, int);
int display(int result[5][5], int, int);
int main()
{
   int arr1[5][5], arr2[5][5], r1, c1, r2, c2, i, j;
   printf("Enter rows and column for first matrix: ");
   scanf("%d %d", &r1, &c1);
   printf("Enter rows and column for second matrix: ");
   scanf("%d %d",&r2, &c2);
   // Column of first matrix should be equal to row of second matrix
   while (c1 != r2)
   {
       printf("Error! Column of first matrix is not equal to row of second matrix.\n\n");
       printf("Enter rows and column for first matrix: ");
       scanf("%d %d", &r1, &c1);
       printf("Enter rows and column for second matrix: ");
       scanf("%d %d",&r2, &c2);
   }
   // Storing elements of first matrix.
   printf("\nEnter elements of first matrix row wise:\n");
   for(i=0; i<r1; i++)
       for(j=0; j<c1; j++)
       {
           scanf("%d", &arr1[i][j]);
       }
   // Storing elements of second matrix.
   printf("\nEnter elements of second matrix row wise:\n");
   for(i=0; i<r2; i++)
       for(j=0; j<c2; j++)
       {
           scanf("%d",&arr2[i][j]);
       }
   multiply(arr1, arr2, r1, c2, c1);
       
   return 0;
}
void multiply(int arr1[5][5], int arr2[5][5], int r, int c, int c1)
{
   int i, j, k, result[5][5];
   
   // Initializing all the elements of result matrix to 0
   for(i=0; i<r; ++i)
       for(j=0; j<c; ++j)
       {
           result[i][j] = 0;
       }
   // Multiplying matrices arr1 and arr2
   for(i=0; i<r; i++)
       for(j=0; j<c; j++)
           for(k=0; k<c1; k++)
           {
               result[i][j]+=arr1[i][k]*arr2[k][j];
           }
    
  display(result, r, c);
}
int display(int result[5][5], int r, int c)
{
   int i,j;
   
   printf("\nResult of Matrix Multiplication is:\n");
   for(i=0; i<r; i++)
   {
       for(j=0; j<c; j++)
       {
           printf("%d\t", result[i][j]);
       }
       
       printf("\n");
    }
    return 0;
}

Output:

Enter rows and column for first matrix: 1 5 Enter rows and column for second matrix: 2 3 Error! Column of first matrix is not equal to row of second matrix. Enter rows and column for first matrix: 1 2 Enter rows and column for second matrix: 2 3 Enter elements of first matrix row wise: 1 2 Enter elements of second matrix row wise: 0 1 3 2 1 4 Result of Matrix Multiplication is:

4 3 11