File I/O, Complete Control the Old-Fashioned Way

Reading and Writing Files Directly

MFC's and App Wizard's built-in serialization capabilities are great if what you are doing is within defined parameters such as stream I/O. But what about an old-fashioned, powerful way of handling files like non-Windows programmers: creating, reading, and writing files directly? There is some nifty code on Code Guru that addresses this issue via custom functions; however, there is a simple, old-fashioned way of handling file I/O at a lower level, and it's VERY powerful!

The MFC Library has the CFile class. Here are the Member Functions of the CFile Class:

As you can see, the CFile class offers real file-handling power. Here is some practical sample code to demonstrate the use of the CFile class. This creates and opens a file, and writes a string to it:

    // Create the file to Write to.
    CFile file("TESTFILE.TXT", CFile::modeCreate | 
                               CFile::modeWrite);
    // Write data to the file.
    CString message("Hello World!");
    int length = message.GetLength();
    file.Write((LPCTSTR)message, length);

Reading from a file isn't much different than writing to one:

    // Open the file to Read from.
    CFile file("TESTFILE.TXT", CFile::modeRead);
    // Read data from the file.
    char s[81];
    int bytesRead = file.Read(s, 80);
    s[bytesRead] = 0;
    CString message = s;

These examples use hard-coded filenames. For a more pleasurable user experience, and to add a nice touch to your programs, use the MFC class CFileDialog (in the online help).