diff --git a/sys/msdos/fonts/README.txt b/sys/msdos/fonts/README.txt
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+The script makefont.lua converts the Terminus fonts from the BDF sources to
+PSF version 2 for use by the MS-DOS NetHack. The directory sys/msdos/fonts
+receives the converted fonts.
+
+makefont.lua is specifically meant for use with NetHack; it rearranges the
+input glyphs so the first 256 positions conform to IBM437. The fonts can then
+support IBMGraphics without using the Unicode table.