C :: Strstr Function / Search And Replacing New String

Code:

#include<stdio.h>
#include<string.h>
#define MAX 25
int main(void)
{
int ch;

[Code]....

i think that cause this program to be error.because when i using the reference from internet, the program was executed for sure.This code what i mean

Code:
#include <stdio.h>
#include <string.h>
#define MAX 10
int main () {
int ch;
char str[] ="This is a simple string";
char str1[MAX];
char str2[MAX];

[Code]....

and rather than that i didnt have anymore idea to make that replacing string.