The Release Notes for each release of X11 specify the changes from the
previous release.  The X Consortium tries very hard to maintain compatibility
across releases.  In the few places where incompatible changes were necessary,
details are given in the Release Notes.  Each X11 distribution site on the
network also offers the Release Notes that go with the release they offer; the
file typically can be found at the top of the distribution tree.

[Stephen Gildea, 1/92]

Things that are incompatible in R6:
	- R6 Xt requires R6 Xlib.
	- R6 Xaw no longer has Clock, Logo, and Mailbox widgets.
	- R6 Xt retains binary compatibility with R5 for all data
	 structures except WMShellPart.  See section 13.4 of the Xt
	 specification for more details.
[Dave Wiggins (dpw@x.org)]

The comp.windows.x.intrinsics FAQ-Xt lists Xt differences among these
versions.

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