If you look closely at a moderate to high compression JPEG image, you will see blotchy areas or banding. If you were to take a picture right off the scanner, save it as a JPEG image with moderate compression, then open it into your image editing software, then save it again in another format, all those defects of compression will be carried over. As a consequence, the JPEG image cannot be edited again once having been compressed and saved. In this document I generally use the full acronym for the graphics format, which may contain four characters. Many graphics formats were developed for Unix systems that allow file names to use almost any combination of letters, numbers or punctuation.
File names can be of almost any length and include spaces.
To accommodate use of these format in the DOS and Windows operating systems, the format names were shortened. The DOS file extension allows only three characters, so JPEG becomes JPG, TIFF becomes TIF, GIF and PNG have only three letters so they can be used as is. By the way, you may someday see the term JFIF used when talking about a JPEG image. Actually, JPEG stands for the specific compression and image encoding formula and JFIF was originally the name of the file format for storing JPEG images. This format is widely used in the desktop publishing community because it stores images with all the quality of the original.