program for multiplication of matrix in c language

C program :

#include <stdio.h>
int main ()
{
int a[' '][' '],b[' '][' '],d[' '][' '];

int i,sum,j,k,r,c,R,C;

printf("enter the size of row for first matrix:");
scanf("%d",&r);
printf("enter the size of column for first matrix:");
scanf("%d",&c);
for (i=0;i<r;i++)
{
  for (j=0;j<c;j++)
{
printf("Enter a[%d][%d]: ",i,j);
scanf("%d",&a[i][j]);
    }
    }
printf("enter the size of row for second matrix :");
scanf("%d",&R);
printf("enter the size of column for second matrix :");
scanf("%d",&C);
for (i=0;i<R;i++)
{
for (j=0;j<C;j++)
{
printf("Enter b[%d][%d]: ",i,j);
scanf("%d",&b[i][j]);
                }
              }
printf("\n printing the first multi dimentional array....\n");
for(i=0;i<r;i++)
   {
printf("\n");
for (j=0;j<c;j++)
{
printf("%d\t",a[i][j]);
  }
       }
printf("\n printing the second multi dimentional array....\n");
  for(i=0;i<R;i++)
{
  printf("\n"); for (j=0;j<C;j++)
  {
   printf("%d\t",b[i][j]);
       }
       }
    if(R != c)
  {
  printf("\n Multiplication not possible");
  }
  else
   {
     for (i = 0; i <= R-1; i++)
     {
     for (j = 0; j <= C-1; j++)
     { sum = 0;
     for (k = 0; k <= R-1; k++)
   {
       sum = sum + a[i][k] * b[k][j];
                                }
    d[i][j] = sum;
      }
                  }
   printf("\nMultiplication Of Two Matrices : \n");
       for (i = 0; i < R; i++)
         { for (j = 0; j < C; j++)
    { printf(" %d ", d[i][j]);
               }
       printf("\n");
               }
                    }
                  return 0;
                      }