Installing Applications from Disk Images

With the advent of packages, many applications do not require installation of additional components in scattered locations. In fact, it is now normal for an application to be just one file, a package (a special folder type that the Mac OS X presents to you like a single file), or a small group of files maintained in the same folder as the application. Thus, the ease of the drag install is currently the norm for Mac OS X applications.

Because of the ease of drag installations, shipping applications as disk image files is one of the most common distribution methods for applications. In fact, Apple uses it for distribution of Mac OS X applications, such as iTunes, iMovie, and AppleWorks.

Disk image files are usually obtained via download from the Internet, which includes the software folder of your iDisk where Apple provides a veritable cornucopia of software for Mac OS X — both from Apple and from third-party developers.

Copy the disk image file to your hard disk and double-click it. The disk image usually has a .IMG, .DMG, or .SMI file name extension (suffix). If the image has an .SMI extension, you may want to just drag it to the Disk Copy window (after launching Disk Copy, of course). Why? Because double-clicking an .SMI file may launch the Classic version of Disk Copy if it is present.

Disk image files mount just like external hard disks, CD-ROMs, or the venerable floppy — ready for you to install your software. To install the application in the Applications folder, you need to be logged in with an administrator account. Just drag the file to the folder where you want it to reside, and you’ll be able to run it from there.