What does it mean to mount or unmount a disk image?
Answer: Mounting a hard disk makes it accessible by the computer. This is a software process that enables the operating system to read and write data to the disk. Most disks are automatically mounted by the operating system when they are connected.
While disk images are not physical disks, they must also be mounted in order for the computer to recognize them. Disk images may be mounted by either the operating system or a disk utility program, such as Nero for Windows or Apple Disk Utility for the Mac. Once the disk image has been mounted, its contents will appear as a physical disk in the computer. However, unlike a physical disk, most disk images are read-only, meaning new data cannot be written to the disk.
Unmounting a disk is, not surprisingly, the opposite of mounting a disk. It takes a mounted disk and makes it inaccessible by the computer. External storage devices should typically be unmounted before being disconnected to avoid corrupting files. Disk images can also be unmounted, which may free up some RAM used by the system to mount the image. To unmount a disk image in Windows, open "My Computer," select the disk image, and click "Eject this disk." In Mac OS X, select the disk image on the desktop and drag the disk image to the trash, which will change to an Eject icon.