defrag [/C] [drive:] [{/F|/U}] [/Sorder[-]] [/B] [/X] [/A] [/FO]
drive: This is the drive letter of the drive you wish to defragment. For instance: defrag c: /C Defrag will not use its menu-driven user interface if you use this option. It will communicate through the command line instead. You must use the [drive:] option, as described above, when you use the /C switch. /F With this option, defrag will perform a full optimisation by making sure that all files are at the beginning of the disk, with no gaps in between. /U With this option, defrag will unfragment the files, but gaps may be left between files. /Sorder[-] Defrag will sort files into the given order: N by Name (alphabetic) E by Extension (alphabetic) D by Date & time (earliest first) S by Size (smallest first) Postfix the order with a hyphen - to sort descending. /B Reboots the computer after defrag completes the optimisation. /X Forces defrag to exit as soon as it completes the optimisation. /A With this option, defrag will give an audible warning before taking action. /FO: For use with the /C option, this tells defrag to give a more full output of information.
Fragmentation is a normal process on DOS disks.