Updated runtime files.
diff --git a/runtime/doc/windows.txt b/runtime/doc/windows.txt
index f4c9001..9bf0960 100644
--- a/runtime/doc/windows.txt
+++ b/runtime/doc/windows.txt
@@ -1,4 +1,4 @@
-*windows.txt* For Vim version 7.4. Last change: 2016 Feb 01
+*windows.txt* For Vim version 7.4. Last change: 2016 Jun 10
VIM REFERENCE MANUAL by Bram Moolenaar
@@ -76,6 +76,16 @@
The main Vim window can hold several split windows. There are also tab pages
|tab-page|, each of which can hold multiple windows.
+Each window has a unique identifier called the window ID. This identifier
+will not change within a Vim session. The |win_getid()| and |win_id2tabwin()|
+functions can be used to convert between the window/tab number and the
+identifier. There is also the window number, which may change whenever
+windows are opened or closed, see |winnr()|.
+
+Each buffer has a unique number and the number will not change within a Vim
+session. The |bufnr()| and |bufname()| functions can be used to convert
+between a buffer name and the buffer number.
+
==============================================================================
2. Starting Vim *windows-starting*