If by chance your Recovery HD is toast, then you can try this:
To display the onscreen keyboard, choose System Preferences→Keyboard→Keyboard tab, and then select the Show Keyboard & Character Viewer in Menu Bar check box. Close System Preferences and click the Input Menu icon that appears in your Finder menu bar — the icon looks like a square containing an asterisk or a country’s flag — and choose Show Keyboard Viewer. Jun 21, 2013 Go to the Apple menu then open System Preferences. Go to “Keyboard” preference panel, and then choose the “Keyboard” tab. Check the box next to “Show Keyboard & Emoji / Character Viewers in menu bar”. Pull down the newly visible Keyboard menu and choose “Show Keyboard Viewer”. Place the keyboard on screen in the desired location, and resize the newly visible keyboard as necessary. Get yosemite for mac.
Jun 16, 2016 Repair the Hard Drive and Permissions - Yosemite, Mavericks, Mountain Lion or Lion. Install OS X Using Internet Recovery. Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything. Jun 25, 2020 R is a language and environment for statistical computing and graphics. It is a GNU project which is similar to the S language and environment which was developed at Bell Laboratories (formerly AT&T, now Lucent Technologies) by John Chambers and colleagues. R can be considered as a different implementation of S. Jul 13, 2014 Yosemite Menu Bar for Rainmeter simulates MacOSX menu bar. It has menus with preset commands and menus that show applications shortcuts that you can easily customize. Start Menu - Rainmeter version of start menu. Applications - Menu with mostly used applications. You can easily customize this menu by opening Application Folder and adding.
Repair the Hard Drive and Permissions - Yosemite, Mavericks, Mountain Lion or Lion
Install OS X Using Internet Recovery
Be sure you backup your files to an external drive or second internal drive because the following procedure will remove everything from the hard drive.
Boot to the Internet Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND-OPTION- R keys until a globe appears on the screen. Wait patiently - 15-20 minutes - until the Recovery main menu appears.
Repair
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When the recovery menu appears select Disk Utility and press the Continue button. After Disk Utility loads select the Macintosh HD entry from the the left side list. Click on the First Aid tab, then click on the Repair Disk button. If Disk Utility reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit Disk Utility and return to the main menu. Select Restart from the Apple menu.
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The above will not replace the Recovery HD. The only way to do that is to install OS X from scratch.