Answer C9

#include <stdio.h>
#include <stdlib.h>
  
int main(int argc, char *argv[])
{
  double sum = 0.0;
  int j;
  
  if ( argc == 0 )
  {
    printf("Nothing entered?\n");
    return 0;
  }
  
  j=1;
  while ( argv[j] )
  {
    sum += atof( argv[j] );
    j++ ;
  }
  printf("sum: %lf\n", sum);
    
  return 0;
} 

A slightly better version that echoes its arguments for error checking:

#include <stdio.h>
#include <stdlib.h>
 
int main(int argc, char *argv[])
{
  double sum = 0.0;
  int j;
  
  if ( argc == 0 )
  {
    printf("Nothing entered?\n");
    return 0;
  }
  
  printf("values:");
  j=1;
  while ( argv[j] )
  {
    double val = atof( argv[j] );
    printf("%lf ", val );
    sum += val;
    j++ ;
  }
  printf("\nsum: %lf\n", sum);
  
  
  return 0;
}