/*  MeanvalueArray.c  (c) Kari Laitinen

    http://www.naturalprogramming.com/

    2013-11-22 File created.
    2013-11-22 Last modification.
*/

#include  <stdio.h>

#define   ARRAY_SIZE     100

int main()
{
   double  array_of_numbers[ ARRAY_SIZE ] ;
   double  number_from_keyboard  ;
   int     number_index   =  0  ;

   printf( "\n This program calculates the mean value of"
           "\n the numbers that you enter from the keyboard."
           "\n The program stops when you enter a letter."
           "\n\n   Enter a number: " ) ;

   /*  The scanf() function returns 'false' if it will not
       get the value it is supposed to be given. */

   while ( ( scanf( "%lf",  &number_from_keyboard ) )  &&
           ( number_index  <  ARRAY_SIZE    )  )
   {
      array_of_numbers[ number_index ]  =  number_from_keyboard ;
      number_index  ++ ;
      printf( "   Enter a number: " ) ;
   }

   int     number_of_numbers_in_array  =  number_index ;
   double  sum_of_numbers  =  0 ;

   for (  number_index  =  0 ;
          number_index  <  number_of_numbers_in_array ;
          number_index  ++ )
   {
      sum_of_numbers  =  sum_of_numbers  +
                         array_of_numbers[ number_index ] ;
   }

   double  mean_value  =  0 ;

   if ( number_of_numbers_in_array  >  0 )
   {
      mean_value  =  sum_of_numbers /
                     (double) number_of_numbers_in_array ;
   }

   printf( "\n The mean value is: %f \n", mean_value ) ;
}