A lost cluster is a cluster on the disk which is marked as being used, but which is not a part of any known file and has no entry in the root directory. Lost chains are made up of these lost clusters. These lost clusters take up disk space and should usually be removed. One of the files will be bad. Using a file name will check fragmentation on that file or files as specified on the disk.
Contiguous files are files that are stored in adjacent sectors on the disk.
Noncontiguous files are those that are stored in non-adjacent sectors on the disk. The reason that you need to be concerned about noncontiguous files is that they access much slower than contiguous files. The user then has the option of converting lost chains into files that can either then be used or deleted. However, it is still a viable command because of its reporting functions. Explain the function and purpose of disk optimization programs.