Figure 13.3  Portion of Program That Uses Functions from a Personal Library
/*
 *  Beginning of source file in which a personal library and system I/O library 
 *  are used.
 */

#include <stdio.h>     /* system's standard I/O functions 	*/
 
#include "planet.h"    /* personal library with planet_t data type and 
operators 	*/
. . .