Matrix Operations

#include <stdio.h>
int r1, c1, r2, c2, i, j, k, sum = 0;
int *ptf, *pts, *ptr;
int first[10][10], second[10][10], result[10][10];
void add()
{
  for(i=0;i<r1;i++)
    for(j=0;j<c2;j++)
      *(ptr+(i*10 +j)) = *(ptf+(i*10+j)) + *(ptf+(i*10+j));
}
void sub()
{
    for(i=0;i<r1;i++)
      for(j=0;j<c2;j++)
        *(ptr+(i*10 +j)) = *(ptf+(i*10+j)) - *(ptf+(i*10+j));
}
void mul()
{

  for ( i = 0 ; i < r1 ; i++ )
  {
    for ( j = 0 ; j < c2 ; j++ )
    {
      *(ptr + (i * 10+j)) = 0;
      for ( k = 0 ; k < r2 ; k++ )
       *(ptr  + (i * 10+j)) += *(ptf + (i*10 + k)) * *(pts + (k*10 + j));
    }
  }
}

int main()
{
  int choice;

  printf("Enter the number of rows and columns of first matrix\n");
  scanf("%d%d", &r1, &c1);
  printf("Enter the number of rows and columns of second matrix\n");
  scanf("%d%d", &r2, &c2);


  printf("Enter the elements of first matrix\n");
  for (  i = 0 ; i < r1 ; i++ )
  {
    for ( j = 0 ; j < c1 ; j++ )
      scanf("%d", &first[i][j]);
    printf("\n");
  }
  printf("Enter the elements of second matrix\n");
  for ( i = 0 ; i < r2 ; i++ )
  {
    for ( j = 0 ; j < c2 ; j++ )
      scanf("%d", &second[i][j]);
    printf("\n");
  }

  printf("First matrix is:-\n");
  for ( i = 0 ; i < r1 ; i++ )
  {
    for ( j = 0 ; j < c1 ; j++ )
      printf("%d\t", first[i][j]);

    printf("\n");
  }
  printf("Second Matrix is:-\n");
  for ( i = 0 ; i < r2 ; i++ )
  {
    for ( j = 0 ; j < c2 ; j++ )
      printf("%d\t", second[i][j]);

    printf("\n");
  }

  ptf = &first[0][0];
  pts = &second[0][0];
  ptr = &result[0][0];

  printf("1. Add 2. Subtract 3. Multiply: ");
  scanf("%i",&choice);
  printf("The result is:-\n");

  switch (choice)
  {
    case 1: add(); break;
    case 2: sub(); break;
    case 3:if ( c1 != r2 )
            {
              printf("Number of columns of first matrix and rows of second matrix must be same.\n");
              return (0);
            }
            mul(); break;
  }

  for ( i = 0 ; i < r1 ; i++ )
  {
    for ( j = 0 ; j < c2 ; j++ )
      printf("%d\t", result[i][j]);

    printf("\n");
  }
  return 0;
}
//Output
//Enter the elements of second matrix
//1
//2
//3

//4
//5
//6

//7
//8
//9

//First matrix is:-
//1       2       3
//4       5       6
//7       8       9
//Second Matrix is:-
//1       2       3
//4       5       6
//7       8       9
//1. Add 2. Subtract 3. Multiply: 1
///The result is:-
//2       4       6
//8       10      12
//14      16      18