// exc4.c   example file  iteration, loops

#include <stdio.h>  // needed to do input and output

int main(int argc, char *argv[]) // argc is count of command line arguments
                                 // argv is list of command line arguments
{
  int i;             // declare loop variable
  int mat[4][3] = {{1,2,3},{2,3,4},{3,4,5},{4,5,6}}; // 4 by 3 matrix
  int sum;

  for(i=0; i<4; i++)  // columns of mat
    {                 // the } could be at end of previous line   
    for(int j=0; j<3; j++) //  j only exists inside loop
    {
      sum += mat[i][j];
    } // end j  optional comment
  } // end i  optional comment
  printf("sum=%d \n", sum);

  for(i=2; i<=10; i=i+2) { printf("i=%d \n",i); } // even numbers
  
  return 0;
} // end exc4.c   optional comment