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Comments
........

   Probably one of the most(1) (Note: Comments-Footnote-1) common
forms of escapes is the comment.

 - Escape: \"
     Start a comment.  Everything to the end of the input line is
     ignored.

     This may sound simple, but it can be tricky to keep the comments
     from interfering with the appearance of the final output.

     If the escape is to the right of some text or a request, that
     portion of the line is ignored, but the space leading up to it is
     noticed by `gtroff'.  This only affects the `.ds' and `.as'
     request.

     One possibly irritating idiosyncracy is that tabs must not be used
     to line up comments.  Tabs are not treated as white space between
     the request and macro arguments.

     A comment on a line by itself is treated as a blank line, because
     after eliminating the comment, that is all that remains:


          Test
          \" comment
          Test

     produces


          Test
          
          Test

     To avoid this, it is common to start the line with `.\"' which
     causes the line to be treated as an undefined request and thus
     ignored completely.

     Another commenting scheme seen sometimes is three consecutive
     single quotes (`'''') at the beginning of a line.  This works, but
     `gtroff' gives a warning about an undefined macro (namely `'''),
     which is harmless, but irritating.

 - Escape: \#
     To avoid all this, `gtroff' has a new comment mechanism using the
     `\#' escape.  This escape works the same as `\"' except that the
     newline is also ignored:


          Test
          \# comment
          Test

     produces


          Test Test

     as expected.

 - Request: .ig yy
     Ignore all input until `gtroff' encounters the macro named `.'YY
     on a line by itself (or `..' if YY is not specified).  This is
     useful for commenting out large blocks of text:


          text text text...
          .ig
          This is part of a large block
          of text that has been
          temporarily(?) commented out.
          
          We can restore it simply by removing
          the .ig request and the ".." at the
          end of the block.
          ..
          More text text text...

     produces


          text text text...  More text text text...

     Note that the commented-out block of text does not cause a break.

     The input is read in copy-mode; auto-incremented registers _are_
     affected (Note: Auto-increment).