i dont know how to create an instream file that can be readable by c++
and how can i know when to use ifstream and ofstream

Tutorial on Input/Output with files
http://www.cplusplus.com/doc/tutorial/files/

ifstream - when you want to read input from an existing file.
ofstream - when you want to write output to a new file.

Chervil wrote:
ofstream - when you want to write output to a new file.

You can also use it to write to an existing file.

@ Peter87 Thanks for the clarification. I was trying to keep things very simple, but sometimes that can be misleading too. :)

and how to create file that c++ can read (like a txt file)
do lots of ways and still fails
ex :
the contain of file :
When I see your face


After running the program, it shows:
Filename: 1.txt
The content:
When I see your face


and my c++ program :
#include <iostream.h>
#include <fstream.h>
#include <assert.h>
#include <windows.h>
#include <conio.h>
#include <stdio.h>
typedef struct Node
{
char character[80];
Node *next, *pre;
}Line;
Line *currentline;
Line *firstline;
Node *head, *tail;
int col;
int row;
void createfirstline()
{
Node *p;
p = new Node;
currentline = p;
head = currentline;
tail = currentline;

}
void newline()
{
Node *p;
p = new Node;
p -> next = NULL;
p->pre = currentline;
currentline->next = p;
tail = p;
currentline=p;

}

void readfile()
{
Node *p;
p = head;
if (head == NULL)
cout << "\nFile is empty!\n" << endl;
else
{
cout << "\nThe content: " << endl << endl;
while (p != NULL)
{
cout << p->character;
p = p->next;
}
}
}
void gotoxy()
{
int x;
int y;
COORD coord;
coord.X = x;
coord.Y = y;
SetConsoleCursorPosition(GetStdHandle(STD_OUTPUT_HANDLE), coord);
}
void main()
{
cout << "Filename: ";
char filename[30];
cin.getline (filename,30);
ifstream instream;
instream.open(filename,ios::in);
if (!instream)
{
cout << "Cannot open the file\n";
}
else
{
char reading;
currentline = firstline;
createfirstline();
while(instream.read(&reading,sizeof(reading)))
{
if (reading == '\n')
newline();
else
{
col++;
currentline->character[col] = reading;
char input;
do
{
input = getch();
switch (input)
{
case 72:
row--;
continue;
case 80:
row++;
continue;
case 77:
col++;
continue;
case 75:
col--;
continue;
}
gotoxy(col,row);
}
while (input != 13);
}
}
}
readfile();
instream.close();
}

can you explain more details about ifstream and ofstream, it still hard for me to understand, what difference between new file and existing file