thank you

I can understand that is is all new to you, and that it is difficult to grasp it all, but why use char array when there is a string class? Why do you refuse to read or look up documentation?
You do #include <string> so why don't you use it?

i doesn't return to loop ,, how can i do??

i got a result:::

#include <fstream>
#include <iostream>
#include <string>
using namespace std;

int main()
{
const int i=20;
char word[i];
int Counter;
cout<<"Enter word to search \n";
cin.get(word,i);


char fileName[80];
string buffer; // for user input
cout << "Enter file name: ";
cin >> fileName;


ifstream fin(fileName);
if(!fin.is_open())
{
cout << "Unable to open file";
system("pause");
exit(1);
}

Counter=0;
while(fin!='\0')
{
getline(fin,buffer);

size_t a = buffer.find(word,0);
if (a != string::npos)
{
cout<<buffer<<endl;
Counter++;
size_t b = a + 1;
a = buffer.find (word, b);
}
}
if(Counter>1)

cout << "Total "<<Counter<<" tLines\n";
else
cout << "Total "<<Counter<<" Line\n";
system("pause");
return 0;
}
____________________________________________

So,how can i link this program to dos??

that should be , because word[i] is a char, and word is a char array
Likewise this should be , otherwise you are comparing the first character only, and not the whole word