Guide to LaTeX (4th Edition) (Tools and Techniques

9.4. Keyword index 227
An entry may be terminated with the character sequences |( or |)
to designate the beginning and end of a range of page numbers. For
example,
\index{table|(} on page 95
\index{table|)} on page 110
produces the entry ‘table’ with page numbers given as 95–110.
Instead of having the page number printed after the entry, a reference
may be made to another index entry. For example, with
\index{space|see{blank}}
\index{table|seealso{array}}
the entries ‘space, see blank’ and ‘table, see also array’ are made in the
index.
The three characters !, @, and | therefore have special functions for
the MakeIndex program. In order to print these characters literally as
text without their functions, the quote character " must precede them.
For example, "! represents a literal exclamation point and not the entry
divider.
The quote character itself is thus a fourth special symbol and must be
entered literally as "". However, there is a special rule in MakeIndex syntax
that says a quote character preceded by a backslash will be interpreted
as part of a command: thus \" may be used to put a German umlaut in
an entry (as in \index{Knappen, J\"org}). This special rule can lead to
additional problems at times: in this book the index entry \! had to be
typed as "\"!.
It is possible to specify varying fonts for the page number. For example,
in the index of this book, page numbers are set in bold face to indicate
the page where a command is defined or first explained. This is achieved
with an entry of the form
\index{blank} on page 11, and
\index{blank|textbf} on page 22
which in the second case puts the page number for this entry as the
argument of a command \textbf. The line in the theindex environment
becomes
\item blank, 11, \textbf{22}
Note: The vertical bar in the \index entry is not a typing error, but
must replace the backslash as the L AT E X command symbol under these
circumstances.
There is a file idx.tex in the L AT E X installation, which can improve the read-
! ability of the .idx files. By processing the idx.tex file (that is, calling latex
idx), the user is prompted for the name of the.idx file to list: