File recovery, data recovery

File recovery entails fixing corrupted files and putting the fixed and uncorrupted files together again in their original structure, in the proper format.

File

A file may become corrupt by incorrect writing to the hard disk, either caused by a virus or malfunctioning of the hard disk.

E-mail

E-mail files with extensions such as .dbx and .pst (Outlook Express and Outlook) as well as Excel spreadsheets (.xls) and Word documents (.doc) can also be restored.

This can be done in different ways. For instance, with a text editor the original data can be read and the right data extracted. This data is then saved in as a new file (Word document, Excel sheet, etc.)

Pictures

Pictures are usually compressed using the JPEG or JPG format. JPEG (Joint Photographic Experts Group) is a standardized compression method to reduce the file size.
Photo viewer programs usually add an icon at the beginning of the files to enable the program to quickly show the pictures as thumbnails.
JPG uses various settings and compression techniques. More compression, resulting in a decrease in quality, can be applied to reduce the time it takes for the pictures to appear on the screen.
Different decoders exist that can create and read JPG files that may vary in quality. However, the difference in quality is usually not detectable by the human eye.
Each picture viewer has its own decoder with different specifications and some decoders are better in repairing damaged files than others.