These classes are used to handle input and output to and from external devices, processes, files etc. as well as manipulating files and directories.
| QAbstractFileEngine | Abstraction for accessing the filesystem |
| QAbstractFileEngineHandler | Way to register custom file engines with your application |
| QBuffer | QIODevice interface for a QByteArray |
| QDataStream | Serialization of binary data to a QIODevice |
| QDir | Access to directory structures and their contents |
| QFile | Interface for reading from and writing to files |
| QFileInfo | System-independent file information |
| QFileSystemWatcher | Interface for monitoring files and directories for modifications |
| QIODevice | The base interface class of all I/O devices in Qt |
| QImageReader | Format independent interface for reading images from files or other devices |
| QImageWriter | Format independent interface for writing images to files or other devices |
| QProcess | Used to start external programs and to communicate with them |
| QProcessEnvironment | Holds the environment variables that can be passed to a program |
| QResource | Interface for reading directly from resources |
| QSettings | Persistent platform-independent application settings |
| QSocketNotifier | Support for monitoring activity on a file descriptor |
| QTemporaryFile | I/O device that operates on temporary files |
| QTextDocumentWriter | Format-independent interface for writing a QTextDocument to files or other devices |
| QTextStream | Convenient interface for reading and writing text |
| QUrl | Convenient interface for working with URLs |
| QUrlInfo | Stores information about URLs |