### 2.7 Comments in Octave Programs

A comment is some text that is included in a program for the sake of human readers, and that is not really part of the program. Comments can explain what the program does, and how it works. Nearly all programming languages have provisions for comments, because programs are typically hard to understand without them.

In the Octave language, a comment starts with either the sharp sign character, ‘`#`’, or the percent symbol ‘`%`’ and continues to the end of the line. The Octave interpreter ignores the rest of a line following a sharp sign or percent symbol. For example, we could have put the following into the function `f`:

         function xdot = f (x, t)

         # usage: f (x, t)
         #
         # This function defines the right hand
         # side functions for a set of nonlinear
         # differential equations.

           r = 0.25;
           ...
         endfunction

The `help` command (see Getting Help) is able to find the first block of comments in a function (even those that are composed directly on the command line). This means that users of Octave can use the same commands to get help for built-in functions, and for functions that you have defined. For example, after defining the function `f` above, the command `help f` produces the output

          usage: f (x, t)

          This function defines the right hand
          side functions for a set of nonlinear
          differential equations.

Although it is possible to put comment lines into keyboard-composed throw-away Octave programs, it usually isn't very useful, because the purpose of a comment is to help you or another person understand the program at a later time.