two apps side by side
El Capitan now lets you run a pair of apps in tandem on a single full screen
1. Max your app
Start by clicking the green button at the top-left corner of one of the two apps you want to use to switch it to full-screen mode. Don’t worry about the menu bar disappearing: moving the pointer to the top of the screen will reveal it.
2. Add your second app
Press the Mission Control key (labelled F3), then hold å and click on your previous space in the top bar (which expands to shown spaces when you put the pointer over it). Now you can see the windows in that space, drag one from a second app on to the first app’s space in the top bar.
3. Reapportion space
As you drag the window over the space, you have a choice of dropping it onto the left or right side. Make that choice, and then click that space.
The two apps now sit side by side in the fullscreen display. Drag the black bar between them to adjust the amount of space allocated to each.