/*
Program to demonstrate pointers (strings)
Version 1.0 / 2001.09.01.
Peter Schindler pstrainer@gmx.net
*/
#include <stdlib.h>
#include <stdio.h>
#include <conio.h>

/*	Declaration of globals	*****************************/
void suba (char x[]);
void subb (char *px);

/*	Main program	*************************************/
void main (void){
int i;
char s[100];
char *ps;

// init string
for (i=0;i<=100;i++) {s[i]='\0';}

printf("Pointer Test Program\n");
printf("Enter a string: ");
scanf("%s",&s);
printf("\n");

//	set pointer ps to the address of s
//	Mind: ps=s is equivalent to ps=&s[0]
//	Therefore s[i] is equivalent to *(s+i)
//	and &s[i] is equivalent to s+i
ps=s;

//	send string (pointer!) to subroutine
printf("main01 s=%s ps=%d\n",s,ps);
suba(s);
printf("main02 s=%s ps=%d\n\n",s,ps);

//	send pointer to subroutine
printf("main03 s=%s ps=%d\n",s,ps);
subb(ps);
printf("main04 s=%s ps=%d\n\n",s,ps);

printf("End of program\n");
_getch();
}

/*	Get string (pointer) and change it ******************/
void suba (char x[]) {
printf("suba01 x=%s\n",x);
x[0]='0';	//	change to '0'
x[1]='1';	//	change to '1'
printf("suba02 x=%s\n",x);
}

/*	Get pointer to string, change chars *****************/
void subb (char *px) {
int i;
char c;
//	print the incoming string
printf("subb01 *px=");
// warning! this does not work:		printf("%s",*px);
i=0;
c='$';
while (c!='\0') {
	c=*(px+i++);
	printf("%c",c);
	}
printf(" px=%d\n",px);

//	change string
*px++='$';	//	change to '$' and inc pointer
*px--='$';	//	change to '$' and dec pointer

//	print the changed string
printf("subb02 *px=");
i=0;
c='$';
while (c!='\0') {
	c=*(px+i++);
	printf("%c",c);
	}
printf(" px=%d\n",px);
}

/*	eof	************************************************/