Exercise 2: Building a Three-Region Layout — Possible Solution
===============================================================

Steps (inside a session):

  vim config.yaml               # window 0, the editor
  Ctrl-a S                      # split: top and bottom regions
  Ctrl-a Tab                    # move to the bottom region (empty)
  Ctrl-a c                      # new window 1 in it
  tail -f /var/log/syslog       # (any log file you can read)
  Ctrl-a |                      # split the bottom region side by side
  Ctrl-a Tab                    # move to the new, empty right region
  Ctrl-a c                      # new window 2
  top

You now see the editor across the top, the log bottom-left and top
bottom-right, all updating at once.

Detach and reattach:

  Ctrl-a d
  screen -r

What you see: normally a single full-size region showing one window.
The split layout has gone. But nothing inside has stopped — switch
with Ctrl-a n and you'll find vim, tail and top all still running.

Why: regions belong to the display (your terminal), not to the
session. When the display detaches, its layout goes with it. The
windows belong to the session, so they survive. Screen's "layout"
commands can save an arrangement if you want to keep it.

WHY THIS WORKS AS AN ANSWER
------------------------------
It walks through the empty-region step that catches most people out,
and uses the reattach to show the difference between regions (display)
and windows (session).