MOUNT.COM is a command inside DOSBox that can connect physical folders and drives to virtual drives inside DOSBox. When you enter the command MOUNT from the DOSBox prompt you should see
Z:\>MOUNT Current mounted drives are: Drive Z is mounted as Internal Virtual Drive
To mount a folder as a drive, follow this basic template.
MOUNT [Drive-Letter] [Local-Directory]
The local directory can be specified relative to the working directory from which DOSBox was started.
To unmount a drive, follow this basic template.
MOUNT -u [Drive-Letter]