You can insert 3.5 inch disks at anytime while using Bat Filer. If the disk is a properly formatted Macintosh disk, it will be mounted by the Macintosh system. You can then see info about the disk in the Mounted Volumes window (see below).
If the disk is not properly formatted, you are given the option to eject, or format the disk.
If you wish to add files to the Bat Filer file list that are located on several volumes, use the "Eject" button in the Add Files dialog to eject a disk; then, insert the next disk you wish to use.
When not adding files, you can eject disks by pressing [Command]-[Shift]-1 to eject from the internal drive, or [Command]-[Shift]-2 for the external.
Do not "overload" Bat Filer with disks. Try to keep the number of mounted, off-line disks to a minimum. Its best to select files from one or two different volumes at a time, do whatever operation you have planned on those files, then click "Clear All Files" to unmount unneeded volumes.
If you have ejected a disk previously mounted, and then access a file on that disk, you will see the "Please insert the disk..." box. When this happens, please do that. Pressing [Command]-[period] to dismiss the "Please insert" box will probably cause an error message soon thereafter.
