Defragmentation is a process that happens with digital files. Files are usually stored in one part. When a disk drive fills up, finding an empty space that is large enough becomes more difficult. When this happens, the file is split into different parts, and each part is stored on a different place in the disk. That process is known as fragmentation. Fragmentation happens because different parts of a file are not stored next to each other. When the file is read, the different parts must be assembled. Fragmented files take longer to assemble. Files that are stored in one part can be read faster. Defragmentation reverses fragmentation and puts the file into one piece.