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What to do when your computer won't turn on

One of the scariest things that can happen to your Mac is a failure to turn on at all. You press the power button and nothing happens - no startup sound, no light, nothing. If this happens, you can check several things before hauling your Mac to the nearest Apple Store for repair.

First, trace the entire flow of electricity to your Mac. Check your Mac's power cord to ensure it is firmly seated where it connects to the computer as well as where it plugs into the wall. If it goes through an outlet strip or a UPS, make sure that's also connected and turned on. Also check that any surge protectors are still working - a power surge might have knocked them off. You can confirm that an outlet is good by plugging in something else, such as a light. If the outlet and all cable connections check out, make sure the power cord has no crimps, breaks, or other damage.

Once you've established that your AC power path is good, it's time to look at your Mac itself. Unplug everything you can - not the power cord, your mouse and keyboard if they're wired, and your monitor if it's not built in - but disconnect everything else and try pressing the power button again. If your Mac turns on, you know that one of your peripherals was at fault.

If your Mac doesn't turn on, it's worth trying to reset your Mac's SMC (System Management Controller), a chip that manages a number of hardware functions - including the operation of the power button. Directions vary by Mac model; see Apple's instructions for details (http://support.apple.com/kb/ht3964).

If you have a Mac laptop, its battery should last through most power outages, so you may not notice that you have a power-related problem until the battery runs out, at which point your Mac might simply appear to be dead. So try all the above tips, but also check your power adapter. If you have an AC cable attached to the adapter (as opposed to a plug going directly into the wall), make sure that cable is securely connected. If you have access to another AC adapter, switch to it briefly - that will tell you whether the original adapter is bad or whether it's something in your Mac itself.

Still no luck? In that case, it's time for professional help. An Apple Store or authorized repair center should be able to diagnose and fix the problem.

Window snapping in macOS Sierra

Mac users now have a window snapping feature built directly into macOS Sierra, which allows users to easily snap windows to aspects of the screen or against one another. This offers a nice way to quickly and precisely align windows, and it's more or less the Mac equivalent feature of window snapping from the Microsoft Windows world.

Window snapping on the Mac will snap windows to any of the following targets: edges of other windows, the menu bar, the top of the Dock (if visible), and the sides of the screen.

With several windows open on the Mac display, grab one and drag it against a snap target. You'll "feel" the dragged window snap to place, repeat with additional windows as desired

The window snapping ability in macOS is a bit more full featured than what is offered in the Windows world, with a broader range of snap targets. You can snap however many windows together that you can fit on screen, regardless of their size.

While you can't completely turn off window snapping, you can temporarily disable window snapping in macOS with a keystroke action when moving windows around on the screen. To temporarily disable window snapping, hold down the Option (alt) key when you're dragging and moving windows around.

Essential keyboard shortcuts for the Open and Save dialog

The next time you end up in an Open or Save dialog window, try out a few of these helpful keyboard shortcuts to make navigating around the dialog and filesystem much faster.

Command+D
Selects Desktop as the destination.

Command+Shift+H
Sets the Home directory as the destination.

Command+Shift+A
Sets Applications directory as the destination.

Command+Shift+.
Toggle invisible items.

Command+Shift+G
Bring up Go To Folder window.

Command+R
Open the selected item in the Finder.

Command+F
Move the cursor to the Find field.

Command+.
Close the Open/Save dialog window.

Spacebar
View the selected item in Quick Look.

Tab
Tab key auto-completes paths and file names from the aforementioned Go To Folder window.

Fine-tune volume and brightness in macOS

When you use the volume controls on a Mac to increase or decrease the sound coming from your speakers, those levels increment in whole steps on a scale from one to ten, press the up volume button once, for example, and the volume goes up one step out of ten. However…

If you hold down Shift and Option (Alt) before pressing the volume keys on your keyboard, you could adjust the volume in quarter-steps instead of whole ones. In addition to using this Shift and Option (Alt) combination to control the volume more finely, you can also use it when you adjust the brightness on your Mac. Press Shift and Option (Alt), then press one of the brightness keys on a Mac keyboard, and you'll notice that the brightness changes in quarter-steps. This is nice if you find your display is just a bit too bright or too dim.

Prepare your Mac for sale

When you get ready to sell or give away your Mac, there are some steps you should take. You'll want to back up your computer, disable some features and services, and erase the hard drive.

Moving to a new Mac? Learn how to move your files to your new Mac. Do this before you erase the hard drive or follow any other steps. 

• Create a backup. Be sure you have an up-to-date backup of your important files and data. Learn how to back up your data in OS X.

• Sign out of iTunes. Open iTunes. From the menu bar at the top of your computer screen or at the top of the iTunes window, choose Account > Authorizations > Deauthorize This Computer. When prompted, enter your Apple ID and password. Then click Deauthorize. Learn more about deauthorizing your computer using iTunes, including how to deauthorize all the computers you've used with your iTunes account.

• Sign out of iCloud. If you use Find My Mac or other iCloud features on your Mac, you should first archive or make copies of your iCloud data. After that, choose Apple Menu > System Preferences, click iCloud, and then deselect the Find My Mac checkbox. Finally, sign out of iCloud. In System Preferences, click iCloud, and then click the Sign Out button. When you sign out of iCloud, you're asked whether you want to remove iCloud data from your Mac. Your iCloud data will remain on any other devices that are using the same Apple ID.

• Sign out of iMessage. If you're using OS X Mountain Lion or later, sign out of iMessage. In the Messages app, choose Preferences > Accounts. Select your iMessage account, then click Sign Out.

• Erase and reinstall OS X. To reformat your hard drive and reinstall OS X, follow these instructions. After you reformat your hard drive and reinstall OS X, the computer restarts to a Welcome screen and asks you to choose a country or region. If you want to leave the Mac in an out-of-box state, don't continue with the setup of your system. Instead, press Command-Q to shut down the Mac. When the new owner turns on the Mac, the Setup Assistant will guide them through the setup process.