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26 GNU Octavethen runs the interpreter with the given argument and the full argument list of the executedprogram. The first argument in the list is the full file name of the Octave program. Therest of the argument list will either be options to Octave, or data files, or both. The ‘-qf’option is usually specified in stand-alone Octave programs to prevent them from printingthe normal startup message, and to keep them from behaving differently depending onthe contents of a particular user’s ‘~/.octaverc’ file. See Section 2.1 [Invoking Octave],page 13. Note that some operating systems may place a limit on the number of charactersthat are recognized after ‘#!’.Self-contained Octave scripts are useful when you want to write a program which userscan invoke without knowing that the program is written in the Octave language.If you invoke an executable Octave script with command line arguments, the argumentsare available in the built-in variable argv. See Section 2.1.1 [Command Line Options],page 13. For example, the following program will reproduce the command line that is usedto execute it.#! /bin/octave -qfprintf ("%s", program_name);for i = 1:narginprintf (" %s", argv{i});endforprintf ("\n");2.7 Comments in Octave ProgramsA comment is some text that is included in a program for the sake of human readers, andthat is not really part of the program. Comments can explain what the program does, andhow it works. Nearly all programming languages have provisions for comments, becauseprograms are typically hard to understand without them.In the Octave language, a comment starts with either the sharp sign character, ‘#’, orthe percent symbol ‘%’ and continues to the end of the line. The Octave interpreter ignoresthe rest of a line following a sharp sign or percent symbol. For example, we could have putthe 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;...endfunctionThe help command (see Section 2.3 [Getting Help], page 16) is able to find the firstblock of comments in a function (even those that are composed directly on the commandline). This means that users of Octave can use the same commands to get help for built-infunctions, and for functions that you have defined. For example, after defining the functionf above, the command help f produces the output