Figure 9.7  Program Using strncpy and strcpy Functions to Separate Compounds into Elemental Components
/*
 *  Displays each elemental component of a compound
 */

#include <stdio.h>
#include <string.h>

#define CMP_LEN  30  /* size of string to hold a compound  */
#define ELEM_LEN 10  /* size of string to hold a component */

int
main(void)
{
    char compound[CMP_LEN];  /* string representing a compound */
    char elem[ELEM_LEN];     /* one elemental component        */
    int  first, next;

    /*  Gets data string representing compound                 */
    printf("Enter a compound> ");
    scanf("%s", compound);

    /*  Displays each elemental component.  These are identified
	by an initial capital letter.                             */
    first = 0;
    for  (next = 1;  next < strlen(compound);  ++next)
	if (compound[next] >= 'A'  &&  compound[next] <= 'Z') {
	       strncpy(elem, &compound[first], next - first);
	       elem[next - first] = '\0';
               printf("%s\n", elem);
               first = next;
	}

    /*  Displays the last component                                 */
    printf("%s\n", strcpy(elem, &compound[first]));

    return (0);
}
/*
Enter a compound> H2SO4
H2
S
O4                        */