Write a C program to read elements in a matrix and find the sum of main diagonal (major diagonal) elements of matrix. Find sum of all elements of main diagonal of a matrix. Logic to find sum of main diagonal elements of a matrix in C programming.

**Example**

**Input**

Input array elements: 1 2 3 4 5 6 7 8 9

**Output**

Sum of main diagonal elements = 15

## Required knowledge

Basic C programming, For loop, Array

### Main diagonal of matrix

Main diagonal of a matrix **A** is a collection of elements **A**_{ij} Such that *i = j*.

Read more – Program to find sum of opposite diagonal elements of a matrix

## Program to find sum of main diagonal elements of a matrix

```
/**
* C program to find sum of main diagonal elements of a matrix
*/
#include <stdio.h>
#define SIZE 3 // Matrix size
int main()
{
int A[SIZE][SIZE];
int row, col, sum = 0;
/* Input elements in matrix from user */
printf("Enter elements in matrix of size %dx%d: \n", SIZE, SIZE);
for(row=0; row<SIZE; row++)
{
for(col=0; col<SIZE; col++)
{
scanf("%d", &A[row][col]);
}
}
/* Find sum of main diagonal elements */
for(row=0; row<SIZE; row++)
{
sum = sum + A[row][row];
}
printf("\nSum of main diagonal elements = %d", sum);
return 0;
}
```

Output

Enter elements in matrix of size 3x3: 1 2 3 4 5 6 7 8 9 Sum of main diagonal elements = 15

Happy coding ðŸ˜‰