Addition of Diagonal Elements in Matrix

#include<stdio.h>
#include<conio.h>

void main()
{
int i,j,a[10][10],sum,m,n;

/* m - Number of rows 
   n - Number of Columns   */

printf("nEnter the number of Rows : ");
scanf ("%d",&m);

printf("nEnter the number of Columns : ");
scanf ("%d",&n);

/* Accept the Elements in m x n Matrix */

for(i=0;i<m;i++ )
       for(j=0;j<n;j++)
       {
       printf("Enter the Element a[%d][%d] : ", i , j);
       scanf("%d",&a[i][j]);
       }

/* Addition of all Diagonal Elements */

sum = 0;

for(i=0;i<m;i++ )
       for(j=0;j<n;j++)
       {
        if ( i == j )
        sum = sum + a[i][j];
       }

/*  Print out the Result */

printf("nSum of All Diagonal Elements in Matrix : %d",sum);

getch();

}

---

Output

Enter the number of Rows : 2

Enter the number of Columns : 2

Enter the Element a[0][0] : 1
Enter the Element a[0][1] : 1
Enter the Element a[1][0] : 1
Enter the Element a[1][1] : 1

The Addition of All Elements in the Matrix : 2

Explanation : 

Considering above 3×3 matrix  -

1. We have to add a[0][0],a[1][1],a[2][2]
2. By Observing , it is clear that when i = j Condition is true then and then only we have to add the elements