Can you have an ifstream and ofstream open for one file at once?

[mosdef]

This is my first post, so please go easy on me .

I intend to both read from and write to a file. Can I have an ifstream and ofstream open for the same file at the same time? Or do I have to close one before I open the other?

Also, will the following code work to ensure the file I am writing to does not already exist, thus preventing overwriting?

    ofstream target_out; // ofstream to write to target file
    bool done = false;
    char targetname[80];

    while( !done ) {
        cout << "Enter data target file: ";
        cin >> targetname;
        target_out.open( targetname, ios::nocreate );

        if( target_out.is_open() ) {
            cout << "The file you entered already exists." << endl;
            target_out.close();
        }
        else
            done = true;

    }

    target_out.open( targetname, ios::noreplace );

Thanks!