TestDisk is free and open-source disk analysis and recovery utility for the Mac OS X operating system. It's primarily intended to aid in recovering lost information storage partitions or make non-booting discs bootable once again even when these conditions are caused by erroneous software, certain kinds of viruses or human errors (like forgetting to erase a hard partition table). In general, this utility allows users to create an image of a failed disk, either lost or not, and then make necessary repairs. This image can later be backed up and stored in a different place, making it easier to retrieve than if the hard drive was completely ruined.
However, one should note that there are some differences between this utility and other similar tools. For one, it's not compatible with all Mac OS X operating systems. It requires a Mac compatible PC or Mac laptop in order to run. Windows users may also find this tool inconvenient since it doesn't work well with this operating systems. Linux users can also expect a bit more difficulty in using the utility, mostly because most people use this as their primary CD/DVD burning program.
This utility can recover fat32 boot sector, formatted partitions, network attached external drives, logical drives and Zip disks. It can also backup encrypted files, restore checksums, restore partially written files and repair corrupted files and folders. This utility is very useful in troubleshooting damaged files, especially if they're part of a larger image or a set of images and have been accidentally deleted by the user or the operating system itself. Although most users can anticipate the need to perform a certain amount of disk recovery or other system troubleshooting tasks with this software, it still helps to know how to do so.