The ability to examine the contents of a hard disk or other storage device at a very deep level has long been a fundamental requirement of technical support personnel and data recovery specialists. They need to analyze the data below the level of the operating system, on a per-byte or per-sector basis, rather than per-file. Those bytes or sectors often comprise current files, but this may not always be the case. Often, the data will represent remnants of deleted files, or information from the partition table, directory structure or other key elements of the copious metadata that exists on every hard disk, CD, DVD, USB pen drive, SD card, and similar devices.
Beyond even the requirements of support personnel and data recovery specialists is a level of device examination product known as forensic examination software.