added a general comment to dwm.h how dwm is basically organized

dwm.h

@@ -1,6 +1,46 @@
 /*
  * (C)opyright MMVI Anselm R. Garbe <garbeam at gmail dot com>
  * See LICENSE file for license details.
+ *
+ * dynamic window manager is designed like any other X client as well. It is
+ * driven through handling X events. In contrast to other X clients, a window
+ * manager like dwm selects for SubstructureRedirectMask on the root window, to
+ * receive events about child window appearance and disappearance.  Only one X
+ * connection at a time is allowed to select for this event mask by any X
+ * server, thus only one window manager instance can be executed at a time.
+ * Any attempt to select for SubstructureRedirectMask by any connection after
+ * another connection already selected for those events, will result in an
+ * error generated by the server. Such errors are reported through calling the
+ * current X error handler.
+ *
+ * Calls to pop an X event from the event queue of the X connection are
+ * blocking.  Due the fact, that dwm reads status text from standard input, a
+ * select-driven main loop has been implemented which selects for reads on the
+ * X connection and STDIN_FILENO to handle all data smoothly and without
+ * busy-loop quirks..  The event handlers of dwm are organized in an array
+ * which is accessed whenever a new event has been popped. This allows event
+ * dispatching in O(1) time.
+ *
+ * Each child window of the root window is called a client in window manager
+ * terminology, except windows which have set the override_redirect flag.
+ * Clients are organized in a global doubly-linked client list, the focus
+ * history is remembered through a global stack list. Each client contains an
+ * array of Bools of the same size as the global tags array to indicate the
+ * tags of a client. There are no other data structures to organize the clients
+ * in tag lists, because a single global list is most simple. All clients which
+ * have at least one tag enabled of the current tags viewed, will be visible on
+ * the screen, all other clients are banned to the x-location 2 * screen width.
+ * This avoids having additional layers of workspace handling.
+ *
+ * For each client dwm creates a small title window which is resized whenever
+ * the WM_NAME or _NET_WM_NAME properties are updated.
+ *
+ * Keys and tagging rules are organized as arrays as well and defined in the
+ * config.h file. These arrays are kept static in event.o and tag.o
+ * respectively, because no other part of dwm needs access to them.
+ *
+ * The current mode is represented by the arrange function pointer which wether
+ * points to dofloat or dotile. 
  */
 
 #include "config.h"