diff -r dbf3a6323fda -r 87e3bb5086e8 README.md
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/README.md	Mon Apr 20 10:14:32 2020 -0500
@@ -0,0 +1,31 @@
+
+# libtu
+
+Written 1999–2007 by Tuomo Valkonen <tuomov@iki.fi>
+
+Libtu is a small utility library for programs written in C, used by my old C codes.
+
+Most of this library may be distributed and modified under either under
+the Clarified Artistic License or the GNU LGPL, version 2.1 or later,
+both reproduced in the file LICENSE. The red-black tree code is under
+the GNU LGPL; see `README.rb` for details.
+
+To build the library, first edit system.mk to customize it for your
+system if necessary. Then `make depend && make`.
+To install it run `make install` (perhaps as root depending on
+where you are installing it).
+
+If you want to use it in your programs, you may try to figure out how
+by reading the header files (`include/*.h`) and test programs (`tester*.c`).
+Or you could try urging me to write some sort of a manual.
+
+## Requisites
+
+Libtu needs the functions asprintf and vasprintf. These do not
+exist on most platforms. One implementation by Mark Martinec
+is included in `snprintf_2.2/` and is used by default. To use the
+system's versions of these functions, if available, modify
+system.mk.
+
+The implementation of red-black trees is based on that by
+James S. Plank; see `README.rb` for details.