The program takes all the images in the first folder and looks for the EXIF info in them. This EXIF info is put there by some digital cameras and includes mayn useful information, including the time and date when the picture was taken. The program reads this time from the picture and adds it in the front of the file name. This way you can have many pictures from different cameras (and different names), that would normally be sorted by camera, not time, and can sort them by time. It is possible to select which information will be added to the file name. The user can select each or any of the following: year, month, day, hour, minute, second and the original file name of the image file.