All readable data is stored in an "ISO" image file which can be read by various software such as "Daemon Tools", "WinRar" (needs iso-plugin) and most burner software like "Nero" etc.
Every succsessfully read sector is stored in the image file (*.ISO) and will be marked "good" in the corresponding "flag" file (*.FLG). If a read error is encountered a dummy sector will be written which will remain marked "bad".
In this case a random number of sectors are skipped for faster progress. Reaching the end of the disk a retry loop will be entered until all sectors have been read or a selectable "Give Up Time" has been reached.
You can download this wonderful tool here