# contains "stdio.h"

# Define the M 3 // matrix order

void main()

{

int a[M][M]，I，j，sum = 0；

Printf ("Please enter %d*%d matrix: \n", m, m);

for(I = 0； I & ltm；; I++)// Enter the M*M matrix.

for(j = 0； j & ltm； j++)

{

scanf("%d "，& ampa[I][j])；

if(I = = j)sum+= a[I][j]； //Find the sum of the elements of the main diagonal.

}

Printf("\n matrix is: \ n ");

for(I = 0； I & ltm；; I++)// output matrix

{

for(j = 0； j & ltm； j++)

printf("%5d "，a[I][j])；

printf(" \ n ")； //Output a newline character every m elements.

}

Printf ("\ nSum of main diagonals =%d\n", sum);

}