A file only really exists if a program can do something with it. Different types of files are handled by different programs. For instance, you write letters is Microsoft Word, but you don’t manipulate photos in it; they have their respective tasks and the files they use/create are often different. MS word files usually have a “.doc” at the end, MS Excel files feature a “.xls,” etc etc. It’s nothing to be alarmed at, it’s simply the computer’s way of flagging the file so that the correct program tries to open it. Some files, of course, can be opened in a few different programs. It’s not to worry about though, as you can select at any time what the default program is to open any particular file type, and can open specific files in the non-default program if you wish, as well. That’s not going to be covered here, but keep an eye out – as the site grows, we’ll be adding more and more articles to help you out!
What’s this .dmg thing?
The .dmg extension is short for “Disk Image.” What’s that? Well, it’s kind of what it’s name implies. It’s a virtual disk that loads once you click on it. See, you can use nifty tricks to compress data into a .dmg file. So let’s say someone has a huge 75MB file. It would take forever to download across the internet, so maybe they have the tools to create a .dmg. Next thing you know, it’s only 45MB, and once you download the .dmg, the computer can re-expand it by opening the virtual disk, and see the entire 75MB file!
These are common tools for developers to get their programs across the internet. Usually, once you open these, and take the things you want off of the virtual disk that appears, you can throw the .dmg file away. But there’s a caveat! Since it’s a disk IMAGE, and the computer recognizes it as a disk once you double-click it, you have to eject the virtual disk first. This can be accomplished by either dragging the Disk Icon to the Trash Can (which will turn into an “Eject” Button when you begin to drag a disk), or you can open the finder and just hit the “Eject” button next to the Disk, which should be in the top half of your sidebar.
What’s this .pdf thing?
PDF stands for Portable Document Format. It’s relatively common, and most every computer can read these files, making them a favorite for companies to use in order to disperse information, especially flyers and paperwork (such as forms & applications to print).
The main drawback is that .pdf files are not easily modified. You can’t open them in just any word processor and change them; you need specialty software such as Adobe Acrobat Pro to do that. But, since 99% of all computers can open & view them, they’re great ways to share things across the internet, because there’s almost no chance for incompatibility.
Use these when you’ve created something you want to share with someone via email, but they don’t have the same program to open the file (say you made a document in Microsoft Word, but your friend doesn’t have Microsoft Word).
Here’s the easy way to make a .pdf file out of anything on the Mac: Open the file in whatever program opens it. Go to File>print, like you’re going to print it. At the bottom of the Print Dialogue on the left side, you’ll see a button labeled “PDF.” Click that and the system will ask you what you want to name it and where you want to save it. Viola! You’ve just “printed” a .pdf file that you can share with anyone across the internet.
What are these .jpg & .gif things?
JPEG is very, VERY widespread image format, as is GIF. They’ve been around a very long time, and in fact a lot of digital cameras output their pictures into the JPEG format. These are pictures you can view on your computer. If you double-click on a .jpg or .gif file, it’ll open in a Program called Preview (which opens most all image formats & also those .pdf files).
If you’d rather not see the generic icon when browsing your files, but instead a small version of the actual picture, you can enable this by making the Finder the active application and navigating to the “View” menu and selecting “Show View Options” (View>Show View Options). Once you’re there, if either the desktop or finder windows with the Icon View enabled are at the font, you can select the option “Show Icon Preview.” Viola again! You have now enabled the OS to show you a small preview of the picture instead of a generic icon. You’ll notice at the top of the View Options Menu Box an option to select whether the changes you make apply to ALL windows, or JUST the one window you have open. You’re choice, if you want every window to take those properties, you are welcome to select that checkbox.
What’s this .exe thing?
That’s trash. Okay, I may be jumping ahead here. An .exe file is a WINDOWS-ONLY file that “Executes” a command and essentially runs an application. A lot of windows viruses get spread using this tool, by getting sent along in an email and the next thing you know, a helpless Windows user has allowed their machine to become infected or contaminated.
You could get this by downloading something from the internet that is Windows-only, or perhaps as an email attachment someone sent to you. And here’s the thing about .exe files in email. Be careful. It’s not that you have to worry, as they won’t hurt you at all. But, you don’t want to forward them to friends your Windows-using friends if it’s a deviant program. How do you know? There’s no special trick, it’s just common sense deduction that’s mostly accurate. If you don’t know who sent it to you, it’s probably suspect. If you get an email from a Windows friend that seems funky, contact them and see what’s up. As general rule, however, just delete these to ensure you don’t accidentally send them to someone and assist in infecting their machine. Better safe than sorry. Sorry like your Windows friends. Zing!
.txt? What’s that?
Files that end with “.txt” are Plain Text files. These are often included with programs you download, usually just simply instructions on how to use. These – much like the .pdf files – are pretty much universal. About 99% of computers are write ".txt" files and read them as well, Mac OS X or Windows. They're far more limited however, as they are true to the implication of their name; they are plain text only! But still, if you just need to compose a few sentences or two, and you want to make sure that the recipient will be able to read it, ".txt" files are a good bet. What's your plain-text creating program? If you navigate to your applications folder, you should find a program called "Text Edit." It's part of the standard package of tools that ships with Apple's Mac OS X.
And with that, the What Are These edition of Quicktips is at a wrap. Use this information to make your experience more efficient & enjoyable!