GNU troff
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This manual documents GNU troff version 1.23.0.

Copyright © 1994--2021 Free Software Foundation, Inc.

     Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with the Front-Cover texts being ``A GNU Manual,'' and with the Back-Cover Texts as in (a) below.  A copy of the license is included in the section entitled ``GNU Free Documentation License.''

     (a) The FSF's Back-Cover Text is: ``You have the freedom to copy and modify this GNU manual.  Buying copies from the FSF supports it in developing GNU and promoting software freedom.''

Built-in Registers
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The following lists some built-in registers that are not described elsewhere in this manual.  Any register name that begins with a . is read-only.  A complete listing of all built-in registers can be found in Register Index.

Here's a stand-alone cross-reference to that index.  See Register Index.  And now one that is (parenthetical; see Register Index).

Register Index
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The macro package or program a specific register belongs to is appended in brackets.

A register name x consisting of exactly one character can be accessed as \nx.  A register name xx consisting of exactly two characters can be accessed as \n(xx.  Register names xxx of any length can be accessed as \n[xxx].