For macs with el capitan, with airplay mirroring, we can have Extend Desktop which lets you use full screen apps on one screen whilst working on something different on another. This is very useful for classrooms where for example a class is working on some questions on an interactive whiteboard connected to an apple tv, and at the same time, the teacher could be recording a roll online without interrupting the student activity.
October 1, 2015
OS X El Capitan 10.11 has been released on the mac app store.
To make a bootable usb format an 8 GB (or preferably 16GB) USB3 drive which should be called Untitled and formatted as Mac OS Extended (Journaled). The installer should be called Install OS X El Capitan.app and should be in your Applications folder.
Run this in terminal and wait about 20 minutes:
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
You can boot up from it by selecting it from the startup manager you get when starting your computer and holding down the option key.
If the installation creates a core storage logical volume you can revert it to get partitions back to normal by running these 2 commands in terminal.
diskutil cs list
diskutil coreStorage revert lvUUID
where lvUUID is the last lvUUID reported by the previous Terminal command.
Then restart for everything to get back to normal after you have run these commands in Terminal.