C02 Answer

#include <stdio.h>
#include <stdlib.h>

/* Puzzle C02 -- print each element in an array of ints, 10 elements per line */

void printArray( int arr[], int size )
{
  const int N = 10;
  int j;
  
  for ( j=0; j<size; j++ )
  {
    if ( j%N == N-1 )
      printf("%4d\n", arr[j] );
    else
      printf("%4d ", arr[j] );    
  }
}

int main(int argc, char *argv[])
{
  int x[] = { 1,  2,  3,  4,  5,  6,  7,  8,  9, 10,
             11, 12, 13, 14, 15, 16, 17, 18, 19, 20,
             21, 22, 23, 24, 25, 26, 27, 28, 29, 30,             
             31, 32, 33, 34, 35, 36, 37, 38, 39, 40 };
  
  printArray( x, 40 );
    
  printf("\n");
  system("pause");	
  return 0;
}

Comments: The modulo operation j%N is used to convert the ascending sequence of array indexes (0,1,2,3,4,5,6,7,8,9,10,11,12,...) into a repeating sequence (0,1,2,3,4,5,6,7,8,9,0,1,2,...). Everytime the repeating sequence hits "9", a newline character is output, which means 10 values are output per line. This use of the modulo operation is common.