First, one must know how to files and programs stored on a hard drive. Of these, the following chart should give you an idea. The structure is shown not entirely accurate, however, illustrates the principle quite well.
To better imagine to what makes necessary at the fragmenting, which is the process which a defragmenting happens, we imagine the space in front as long strips, so a "rolled out" hard drive.
Thus, a contiguous defragmented part looks like the hard drive. Each file or program is stored in one piece.
Now we install a new program, which is white in the first free (white pictured) part because it does not fit cut, and stored the rest in another free part
Thus, the computer now knows where the second part (there may be many more) is located, must be set at the end of the first part is a kind of guide. This costs additional space and increases the load times because the disk must always jump from strand to strand.
Thus, our disk will look like after a while.
And so then after defragmenting.
Defragmenting also helps save some space on a permanent basis and may make the loading times of files and programs significantly shorten.
Defragment TIP: Every 3 months.