If you are new to the Mac, you will obviously want to try out new applications. How does one install those applications though? Even if you have managed to get some applications working, for the purpose of this tutorial, just assume that you do not know how to install them. And I’m not saying that just to get you to read this tutorial either—it’s entirely possible that you think you’ve got it right but are in fact doing it all wrong.

There are two basic ways to install applications on Mac OS X:

1. The first and most common approach works for apps that are enclosed in a disk image. Think of it as a virtual CD-ROM.

After you download a disk image (Firefox.dmg, for example), you’ll need to first mount it onto your desktop. Just double-clicking it should do the trick, assuming that it wasn’t automatically mounted for you beforehand. Once you do that, you will notice that it creates a virtual image on your desktop and in the Finder sidebar. For certain applications, it might also automatically pop open a window.

Once you open the mounted image now (assuming that it didn’t do so automatically), you will notice that the application resides in there. Do not double-click on the application icon and run it from there. This is the part where most new users, accustomed to the Windows way of doing things, go wrong.

Since this is just a mounted disk image, running the application from here is akin to watching a movie on a DVD. Once you eject the disk, the movie goes along with it unless you’ve ripped and saved it on your Mac. Similarly, to give this application a permanent home on your Mac, you need to copy it from the disk image and paste it somewhere on your Mac’s hard disk (preferably in the applications folder). In this case, the developer has put the Firefox application and provided the applications folder alias so you can directly drag the Firefox icon into the Applications folder, as the graphic illustration indicates.

(You can click the little pill to get into full Finder mode.)

You might also come across barebones disk images, ones will have to copy the application from into the applications folder on your hard drive. There won’t be any fancy illustrations to guide you and they won’t automatically pop open for you. In either case, once you have copied the application, you will need to eject the disk image, much like you would eject a CD.

To eject a disk image, simply drag it from your desktop to the trash or click the eject button beside its name in the Finder sidebar. Whenever you want to launch the application now, you can do so from the applications folder on your hard drive. For the sake of convenience, you could drag the application onto your Dock, but only from the applications folder on your hard drive, not the disk image. Another option is to hit ⌘-Space to invoke the Spotlight search field, type the first few letters of its name and hit return (yes, it actually works, for a change).

2. The second method is used for more complex applications which require access to the internals of the system—Photoshop, iTunes and applications of the iLife suite being some examples. In this case, you may get a similar disk image but the file inside it will generally not have the icon of the application, instead sporting an open box. It might also spell the words “Install XYZ” or “Setup”. In this case, double-click on the installer and proceed with the instructions much like you did on a Windows PC. Note that you will need to give your administrator password in most cases so be sure that you are not installing anything that may be malicious in nature, although the chances of that are extremely rare on a Mac (to the point of being practically non-existent).

Deleting: Once you have your application up and running, what if you decide that it doesn’t quite live up to the hype after all? How does one go about getting rid of an application, specially given that there is no “Add/Remove Programs” system on Mac OS X? To delete an application you select it in the applications folder, and drag it to the trash. It is as simple as that. You do not need to worry about the tiny preference files that the application might create as they do not affect the system.

However, that only applies to applications installed via the first method. Applications that get installed through an installer, on the other hand, need to be uninstalled the same way. You need to run the installer again and choose the option to uninstall it this time. Simply deleting the application from your hard drive in this case will only remove the front-end of the app, leaving it’s inner workings behind to wallow in your system folder. It’s always advisable to use the installer instead.

Things you need to know:

• The application file (with the ‘.APP’ extension) is actually a special kind of folder. In this case, if you right-click on Firefox and select “Show Package Contents”, you will see all the internals of the application residing in that app folder.
• Windows executables (EXEs) will not work on the Mac so you can’t expect to install Windows applications. There are, of course, better applications for the Mac in most cases, so you don’t need to worry about that.
• You don’t need to worry about viruses when installing applications by the first method. As long as you don’t give your username and password, the application cannot do any damage to your system. (Ed note: Don’t tell anyone that you heard this here but even applications that do ask for your username and password are fairly trustworthy on the Mac, given the fact that there isn’t a single known virus for Mac OS X in the wild as of this writing. Shhh!)

Tagged as: applications, Basics, beginners, guide, switchers, tutorial