Editing Literate programming (section)

=== Creation of macros ===
The following snippet of the <code>wc</code> literate program<ref name="noweb-wc" /> shows how arbitrary descriptive phrases in a natural language are used in a literate program to create macros, which act as new "operators" in the literate programming language, and hide chunks of code or other macros. The mark-up notation consists of double angle brackets (<code>&lt;&lt;...&gt;&gt;</code>) that indicate macros. The <code>@</code> symbol which, in a noweb file, indicates the beginning of a documentation chunk. The <code>&lt;&lt;*&gt;&gt;</code> symbol stands for the "root", topmost node the literate programming tool will start expanding the web of macros from. Actually, writing out the expanded source code can be done from any section or subsection (i.e. a piece of code designated as <code>&lt;&lt;name of the chunk&gt;&gt;=</code>, with the equal sign), so one literate program file can contain several files with machine source code.
<syntaxhighlight lang="c">
The purpose of wc is to count lines, words, and/or characters in a list of files. The
number of lines in a file is ......../more explanations/

Here, then, is an overview of the file wc.c that is defined by the noweb program wc.nw:
    <<*>>=
    <<Header files to include>>
    <<Definitions>>
    <<Global variables>>
    <<Functions>>
    <<The main program>>
    @

We must include the standard I/O definitions, since we want to send formatted output
to stdout and stderr.
    <<Header files to include>>=
    #include <stdio.h>
    @
</syntaxhighlight>
The unraveling of the chunks can be done in any place in the literate program text file, not necessarily in the order they are sequenced in the enclosing chunk, but as is demanded by the logic reflected in the explanatory text that envelops the whole program.