Visible comments

/* ... */ is a long comment (it may extend over several lines).

// ... is a short comment (terminated by the next newline).

@(...@) is a meta-comment. Meta-comments are a localized form of the N mode (see Languages). Tangled meta-comments are begun by the contents of the style-file entry meta.top and terminated by meta.bottom. Each line of the meta-comment is begun by meta.prefix. Woven meta-comments are begun by meta_code.begin and ended by meta_code.end. See Miscellaneous params.

     @n
     @a
             program main
     /* Get input. */
             call get_input // Read the parameter file.
     /* Process information.  Comments like this
        can be split over several lines. */
     @(
     Meta-comments provide a poor-person's alignment feature
      i --- counter
      x --- data value
     @)
             i = 1
             x = 2.0
             call exec(i,x)
             end
     

The use of meta-comments is not recommended; they are only marginally supported. Use ordinary long comments instead. Inside of them, use the various powerful features of TeX or LaTeX (such as \halign or \begin{verbatim} ... \end{verbatim}) to format your comment appropriately.