Use the mtools programs to work with ms-dos based files, execute mtools for a full listing of available m* tools. There are a lot of files within the mtools package for working with ms-dos disks, also try the info documentation of mtools for more details.
The use of slashes: Note that with mtools commands you can use the slashes on the a: part either way (ie. backslash (windows-style) or forward slash (UNIX system style)).
mcopy a:/file_or_files /destination/directory
mmount a: /mnt/floppy
This program is used to check and repair ms-dos based filesystems. Use the -a option to automatically repair the filesystem (ie don't ask the user questions), the -t option to mark un-readable clusters as bad and the -v option to be more verbose (print more information).
dosfsck -at /dev/fd0