Both programs and data have filenames and often extensions that further identify the type or purpose of the file. After reading the above definitions it is easy to see that there are number of important aspects of filing systems. The extension .dll refers to the fact that this file is a 'dynamic link library' file. The concept of file extensions is an important one and a seperate document covering this aspect should be read. Such fragmentation slows disk access and degrades the overall performance of disk operations, although usually not severely.
Utility programs are available for rearranging file storage on fragmented disks.
This process is known as 'defragmentation'. The process of fragmentation and defragmentation is shown in the following figure.