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

int main ( int argc, char *argv[] );
void test_a ( );
void timestamp ( );

/******************************************************************************/

int main ( int argc, char *argv[] )

/******************************************************************************/
/*
  Purpose:

    matrix_test() demonstrates the use of a doubly indexed matrix in C.

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    30 September 2024

  Author:

    John Burkardt
*/
{  
  timestamp ( );
  printf ( "\n" );
  printf ( "arrays_test():\n" );
  printf ( "  C version\n" );
  printf ( "  Set up a matrix with 5 rows and 4 columns.\n" );

  test_a ( );
/*
  Terminate.
*/
  printf ( "\n" );
  printf ( "arrays_test():\n" );
  printf ( "  Normal end of execution.\n" );
  printf ( "\n" );
  timestamp ( );

  return 0;
}
/******************************************************************************/

void test_a ( )

/******************************************************************************/
/*
  Purpose:

    test_a() demonstrates the use of a doubly indexed matrix in C.

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    30 September 2024

  Author:

    John Burkardt
*/
{
  int a[5][4];
  int i;
  int j;
  int k;

  printf ( "\n" );
  printf ( "test_a():\n" );
  printf ( "  Use 'int a[5][4]' to create a doubly dimensioned array.\n" );
  printf ( "  Show how to assign values.\n" );
  printf ( "  Show we can use [i][j] double index to inspect values.\n" );
/*
  Use double indexing to set values.
*/
  for ( j = 0; j < 4; j++ )
  {
    for ( i = 0; i < 5; i++ )
    {
      a[i][j] = 10 * ( i + 1 ) + ( j + 1 );
    }
  }
/*
  We can access values using two indices.
*/
  printf ( "\n" );
  printf ( "  The matrix A[][]:\n" );
  printf ( "\n" );
  printf ( "       i       j       k    A[i][j]\n" );
  printf ( "\n" );

  k = 0;
  for ( i = 0; i < 5; i++ )
  {
    for ( j = 0; j < 4; j++ )
    {
      printf ( "  %6d  %6d  %6d  %6d\n", i, j, k, a[i][j] );
      k = k + 1;
    }
  }

  return;
}
/********************************************************************/

void timestamp ( )

/********************************************************************/
/*
  Purpose:

    timestamp() prints the current YMDHMS date as a time stamp.

  Example:

    May 31 2001 09:45:54 AM

  Licensing:

    This code is distributed under the MIT license. 

  Modified:

    03 October 2003

  Author:

    John Burkardt

  Parameters:

    None
*/
{
# define TIME_SIZE 40

  static char time_buffer[TIME_SIZE];
  const struct tm *tm;
  time_t now;

  now = time ( NULL );
  tm = localtime ( &now );

  strftime ( time_buffer, TIME_SIZE, "%d %B %Y %I:%M:%S %p", tm );

  printf ( "%s\n", time_buffer );

  return;
# undef TIME_SIZE
}