Problem writing ASCII characters in file

Hi,
I wrote a program to convert decimal numbers 0 -254 to characters and write it in a file. The program reads the characters back and gives the corresponding decimal numbers. But when I write corresponding characters of numbers 10,11,12, and 13, the program reads them back as 204. I cannot figure out how to get 10,11, 12 and 13 back. Any help will be appreciated. Here's the code:

Code:

---

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

int main ()
{        int x = 11;
        ofstream outfile ("output.dat", ios::out);

    if (!outfile)
        {                 
                exit (1);
        }
                      outfile<<( unsigned char)(x);
                outfile.close();

    int p;
    char ch;
        unsigned char ch1;
        ifstream infile;

        infile.open("output.dat");

        if (!infile)
        {       
                exit (1);
        }

        while ((ch= infile.peek()) !=EOF )
        {
                infile >> ch1;

    p = int (ch1);

                cout<<p<<endl;
        }

        infile.close();
       
        return 0;
}

---

Note that peek() returns an int, not a char.

Code:

---

int ch;
ch= infile.peek();

---

Also

Code:

---

infile >> ch;

---

Won't put anything in ch1 if there is a problem with the stream. You could check this by putting a value in ch1 before that line and outputting the value afterwards.

Code:

---

ch1 = '@';
infile >> ch1;
cout << "ch1=" << ch1 << endl;

---

Four things:
> ofstream outfile ("output.dat", ios::out);
Open the file in binary mode:

Code:

---

        ofstream outfile ("output.dat", ios::binary);

---

> outfile<<( unsigned char)(x);
Use put here:

Code:

---

                      outfile.put(x);

---

> infile.open("output.dat");

Again open the file in binary mode:

Code:

---

        infile.open("output.dat", ios::binary);

---

> infile >> ch1;
Use get here:

Code:

---

                ch1 = infile.get();

---

Or

change

Code:

---

infile >> ch1;

---

To

Code:

---

infile >> noskipws >> ch1;

---

As ASCII characters 10,11, 12 and 13 are whitespace.

sho1,

Here's why you have to use binary mode to read/write these values:

When you read/write a file in text mode (the default mode) the data is changed. Lines of text on the disk are stored differently from the way strings are stored in C++.

A line of text on a disk is terminated with a carriage return (13) and/or line feed (10) depending on your operating system.

When you save a string (in text mode) these values are added to the file. When you read a line from a file, these characters are not included in the string.

With C-style strings, the null-termination is thrown-away and replaced by carriage return/line feed when you save a file (in text mode).

When you read a line from a file (in text mode) into a C-style string, the carriage return/line feed is replaced with the null-termination.

I'm not exactly sure why you are having trouble with 11 and 12, except that maybe you are reading the numbers in sequence, and it gets fouled-up as soon as it reads 10.

>I'm not exactly sure why you are having trouble with 11 and 12
Maybe because 11=VT (Vertical Tab) and 12=FF (Form Feed).